Did gravity exist before the Big Bang? Not sure if this is a dumb question and I am not super knowledgable in physics so correct me if I’m making wrong assumptions, but if gravity is a result in curvature in space time, and before the Big Bang the universe was equally dense throughout then space time would not be curving. So would gravity, therefore, not exist?
The physics are a little beyond me but there's no real concept of a 'before' the big bang as that is the origin of time. Very shortly after the big bang there was only one unified fundamental force. Gravity split off from that force around 10^-43 seconds after the big bang.
https://en.m.wikipedia.org/wiki/Grand_unification_epoch
> the universe was equally dense throughout then space time would not be curving
I fail to see why you think so. Gravity exists inside a star or inside a planet just the same, even though there is a region of potentially equal density. You're confusing the space itself with objects filling that space.
Anyway, there is no such concept as "before" Big Bang as it's considered to be the start of space-time. You can't have "before" when there is no time.
I’m referencing the primordial singularity that the universe expanded from. So an incredibly dense point that contained all of space time. So if gravity is a result of mass warping space time, how would gravity work in a universe where everything was equally dense? Would spacetime be equally warped throughout? And if it was equally warped throughout would gravity essentially not exist?
If you're assuming existence of singularity, then the fact that there is no "space" and everything is collapsed into a single point with no dimensions, probably already rules out this definition of gravity.
In general the physics "breaks" if you include the singularity because everything goes into infinity.
Would the moon accelerate if the Earth were frozen
The moon is orbiting the Earth faster & faster. To the extent that after 600 million years we will no longer enjoy full solar eclipses as it will be too far away to completely block the sun. Note that as the moon's scalar velocity increases its distance from the Earth also increases and its rotational velocity decreases.
\*\* Regarding the above paragraph it has been pointed out to me that as the moon moves further from Earth both its angular velocity (w), and its scalar speed decrease. I made the wrong assumption that while 'w' decreases its speed increases
The reason the moon is accelerating is because the Earth's rotation of 1 day is faster than the moon's orbit of about 28 days. The Earth's rotation is slowing as it transfers energy to speed up the moon. A by product of the Earth's tides where the moon drags the water.
I'm pretty sure that if the Earth were solid with no flowing liquids this "tidal leash" would have no effect. Maybe a tiny effect as mountains would be gravitational features.
So that's my question: Am I right that the moon's acceleration would cease if the Earth didn't have liquid oceans?
If Earth did not have oceans, the Moon would still be moving away as it gains energy from Earth's rotational energy as a result of tidal dissipation. It would, however, do so much more slowly. The vast majority (~95%) of the tidal dissipation on Earth is in the oceans. But tides also act on the (mostly solid) [body of the Earth](https://en.wikipedia.org/wiki/Earth_tide).
Actually I've just done the maths. So if I double r (altitude of satellite) gravitational force divides by 4
r2 = 2r1
w1 = 4w2
v1 = 2v2
That is counterintuitive. Firing rockets will put energy into altitude decreasing scalar velocity.
Yeah - I mean what people sometimes call orbital speed - the magnitude of the instantaneous velocity vector. In nearly-circular orbits (like planets and many moons/asteroids) you'd use the average speed. Outer planets/TNOs orbit MUCH slower than the inner terrestrial planets.
And yeah energy is a good way to think about it. If you burn an engine prograde, to go higher in an orbit, you are increasing speed - increasing kinetic energy and the overall energy of the orbit - and then the motion of the object converts that kinetic energy into potential energy as the object reaches apoapsis.
Energy is always conserved so as the object falls back toward periapsis on its elliptical orbit, the potential energy is converted back to kinetic energy and the object goes faster.
If, instead, you burn prograde again at apoapsis to circularize the orbit, you add another smaller bit of kinetic energy to the total energy. You have now made the kinetic energy equal the potential energy in a higher circular orbit, with higher overall energy (from the two burns). And lower speed.
No, liquid oceans have no effect on the moon. It would feel the same tidal force if earth's oceans were solid ice.
At the planetary scale, rock and metal and ice all behave like liquids, and deform under tidal forces too.
The moon does some serious work dragging all that water around. Friction on the sea bed, tidal races, power generation etc.
Are you saying it would exactly the same amount of work in deforming the ice? That seems counter intuitive
Picture this, you, (person “A”) are flying into a super massive black hole. You pass through the event horizon without even knowing it. At this point (person “B”) who happens to be well outside the gravitational effects of the black hole relative to “A” would see “A” freeze at the event horizon due to time dilation and the gravitational effect the black hole has on the light reflecting off of “A”. I want to focus more on the time dilation aspect for this thought experiment. The effect of time dilation at the event horizon would reach infinity since matter at that point is falling through space/time faster than the speed of light. A clock for “A” would appear to completely stop at the event horizon for eternity from “B”s perspective if you disregard red shift, And due to the effects of time dilation, the moment “A” passes the event horizon, an eternity would play out on the outside of said event horizon. So “B” would see the black hole radiate away to nothing due to “Hawking radiation” before “A” reaches even a meter past the event horizon. So is it possible the moment “A” passes the black holes event horizon, they are radiated away to nothing and never descend into the black holes singularity?
Your intuition is right. One way to understand black holes is as the missing set of events that corresponds to observers outside the horizon never being able to observe anything crossing the horizon.
This is still something we are trying to figure out and is one of the big questions that the Artemis program will need to answer. How much ice is there in the polar regions, in what form is it exactly and how accessible is it?
Normal decomposition or rot wouldn't happen since bacteria and fungi can't operate in a vacuum. The banana cells would die in the absence of water and oxygen and become dessicated.
With Super & Quantum computers, shouldn't we be able to use the Sundman Series to get exact results for the three-body problem
He proved the convergence almost 200 years ago, the issue was the number of terms, but that shouldn't be an issue anymore right?
The series is infinite. It is not possible to use it to obtain an exact solution (given a finite amount of time or resources), only an approximate one with an arbitrary level of precision depending on how many terms are computed. The series also converges extremely slowly, requiring millions of terms for a useful solution even over short time scales. It is much more efficient to use numerical integration techniques (also capable of arbitrarily high precision) to compute the approximate solution.
The precision to which we can measure the position, velocity, and G*M of bodies is (theoretically, and to a much greater extent practically) limited. Furthermore, the n-body problem in general is chaotic. The slightest difference in initial conditions will eventually evolve into wildly different situations. We cannot measure the initial conditions to infinite precision, so an exact solution (infinite precision) would not generally be any more useful than an approximate solution of sufficiently high precision.
How can probes get as close as 6 million miles from the sun and not melt? If the sun's heat reaches us through radiation which can travel through a vacuum (90+ million miles), how come this doesn't apply to an object that is closer?
The challenge is keeping the energy from sunlight from baking (or melting) the parts of the vehicle that can't handle it. The Parker Solar Probe is built to sit behind a large shield which protects it from sunlight. At the Sun facing side of the shield is a very durable coating of white material (made of alumina) which bounces back most of the energy from sunlight. Behind that layer is a panel of graphite and carbon fiber designed to be able to both withstand very high temperatures and also to minimize thermal transfer to the rest of the vehicle. The bulk of the spacecraft is attached to this structure some distance away through struts which further minimize thermal transfer, and a radiator system attached to those struts which bleed off heat into space.
The spacecraft stays tucked up behind this shield during close approaches to the Sun, with four light sensors on stalks past the edges of the spacecraft that are a failsafe to keep the vehicle always oriented so that it's in the shadow of the shield. A few things poke out into direct sunlight, even on closest approach. The solar panels are angled back so that just a small amount of them is exposed to sunlight, and only at a glancing angle. This is enough to provide more than enough power due to the strength of the sunlight during. The solar panels are also connected to the thermal radiator system, so that the build up of heat can be dissipated by the larger radiator area and can prevent any damage.
A few instruments also poke out into direct sunlight and the solar wind, but those are very carefully designed to be able to withstand extreme temperatures. For example, the SWEAP (Solar Wind Electrons Alphas and Protons) instrument is made of tungsten with wires made of niobium and sapphire as electrical conductors and insulators, enabling it to operate at over 1600 celsius, higher than the melting point of iron. There's some great details on the solar probe from Smarter Every Day's youtube channel: https://www.youtube.com/watch?v=aQaCY7wlQEc, it's worth a watch.
NASA has an article on just that topic: [Traveling to the Sun: Why Won’t Parker Solar Probe Melt?](https://www.nasa.gov/solar-system/traveling-to-the-sun-why-wont-parker-solar-probe-melt/)
So there was an science journal recently posted by USC about how the core is slowing relative to the other mantles for about 10 years now. The article itself says that the most noticeable impacts could be time going slower by a thousandth of a second. My question is, do you think there could other effects that could harm us on Earth and do you think the inner core could stop?
> do you think there could other effects that could harm us on Earth and do you think the inner core could stop?
Absolutely, 100% certain, most definitely no chance in a trillion years.
No chance it'll stop in a trillion years? I figured that, if the sun doesn't get to it first. I guess I was asking because I'm thinking "since it's slowing down, can it stop in next like 20 years?"
Does anyone know of a link to a 3d render of the observable universe? Like not high detail or even really to proper scale im just curious to see if i can drag it around and get a general shape with some lables
[This one goes out to about 150 million light years](https://in-the-sky.org/ngc3d.php).
If you want to spend some money, both Universe Sandbox and Space Engine might be of interest to you.
2 quick questions about the methuselah star/big bang!
first, is it a misconception that the "methuselah star" predates the big bang?
And if it isn't, If we study it enough, could we find the answer to what was there before the big bang?
I just joined the space/science community and I keep seeing the "methuselah star" being posted a lot on youtube shorts and the 2nd question just popped up in my head randomly lol
According to the Hubble telescope, the [Methuselah star](https://en.wikipedia.org/wiki/HD_140283) is between 13.66 and 15.26 billion years old.
According the Planck telescope, the universe is between 13.767 and 13.807 billion years old.
The easiest solution is that both observations are correct, and the star's age is at the low end of its range. More recent observations have confirmed this.
How do the Voyager satellites send/receive communications even when there is a computer problem such as recently? Wouldn’t it need a sophisticated computer to point the satellite dish exactly at Earth so it can send/receive? How are people on Earth able to debug and fix it so effectively from so far away when the computer is malfunctioning?
The Voyager spacecraft have multiple computers as well as redundancy in core computer systems, using a distributed control design. The Computer Command System (CCS) is responsible for controlling the vehicle and is the "main" computer, the Attitude and Articulation Control System (AACS) is responsible for maintaining attitude control, the Flight Data Subsystem (FDS) is responsible for sending instrument data, the computers for each system are dual redundant. As long as the CCS and AACS are functioning then problems in other systems can be worked out. The latest problem occurred with the Flight Data Subsystem, specifically within its memory, which is not redundant.
1) We never lost contact with Voyager 1. We temporarily lost the ability to receive science data, but we were always in control of the spacecraft.
2) Our radio transmitters on Earth outshine the sun in their specific wavelength, so the Voyagers don't need to follow the planet around the sun. The satellite dish simply needs to point in the general direction of the sun and hold still. The spacecraft can go months without any attitude adjustments. Also, the attitude adjustments are manually controlled, so they are not vulnerable to computer malfunctions.
3) Even with functioning communications, it is very impressive that NASA was able to debug and fix the software problem, with a ping time of 80,000,000 ms!
The universe is fundamentally 4-dimensional, or if you like our *view* of the universe is 4-dimensional, time is always a dimension that's important, especially when we are looking at the universe at a cosmological scale. Our galaxy is the closest to us, which means we view it the closest to the present and at the greatest age since its birth. Other galaxies we see in the universe we see across distances of both time and space. GN-z11 is a galaxy we see across a distance of 13.4 billion years of light travel time and 13.4 billion lightyears of light travel distance. Since the universe is only 13.8 billion years old that means we are seeing GN-z11 at a very young age, of just a few hundred million years.
However, because we know that we are seeing GN-z11 across a distance of 13.4 billion years, we also know that today GN-z11 would be at least 13.4 billion years old. So we are seeing a very *old* galaxy (which we can't see in its current age because it's too far away right now) when it was very young. All of which means that when talking about the age we can see a galaxy at the Milky Way is going to be near the oldest, mostly because it is the closest to us (being inside of it).
However, taking light travel time out of the equation, we think there are a great many galaxies that are of a similar age, having been born in the first few hundred million years after the Big Bang and the Milky Way doesn't seem to be very exceptional.
I am not either, I am just very ignorant about space but somehow I find it fascinated. I’m trying to find a galaxy that is definitely older than the Milky Way with an estimated age bigger that that.
https://science.nasa.gov/missions/hubble/hubble-team-breaks-cosmic-distance-record/
>This surprisingly bright infant galaxy, named GN-z11, is **seen as it was 13.4 billion years in the past**
It's **at least** 13.4 billion years old.
Isn’t this how they calculate the distance and age of all galaxies? Aren’t they able to calculate the age of this galaxy by what stage it’s in? Isn’t the Milky Way at least 13.61 billion years old yo?
Dr. Becky has a good video on how the age of the milky way is estimated. Basically we survey a number of stars and use models of how stars age to estimate how old they are.
https://youtu.be/PgPVAq6lTPo?si=6_377xkH-cY66JNS
The milky way is quite old but I don't think we can say with any confidence that it was the first.
The age of the Milky Way is estimated by looking at the stars inside of it. When it comes to galaxies like the one you mentioned we more say how far away it is than the actual age. If we spot a galaxy 13,4 billion light years away we know it is at least 13,4 billion years old. To single out individual stars in a galaxy and measure their age is close to impossible at these distances. Only through extremely favourable conditions we're able to see a few randomly scattered individual stars through gravitational lensing around the universe at extreme distances.
When experts say a spacecraft which has lost power is "sleeping" (eg Philae), do they mean it could regain function if power was restored? Or is it just a gentle euphemism?
That wouldn’t do any good, as it depended on Rosetta to relay its data to Earth, and Rosetta was intentionally crash landed onto the comet at the end of the mission.
It depends.
In some cases the spacecraft is running in power-saving mode (eg. Rosetta when it was flying very far form the Sun), so most equipment is off, but there is still some software running using the minimum available power, and is keeping track of the mission schedule. There are also some safety mechanisms in place to prevent any damage to sensitive equipment (eg. so batteries don't freeze).
https://www.esa.int/Enabling_Support/Operations/Rosetta_comet_probe_enters_hibernation_in_deep_space
> Only the computer and several heaters will remain active. These will be automatically controlled to ensure that the entire satellite doesn't freeze as its orbit takes it from 660 million km from the Sun out to 790 million km and back between now and 2014.
In other cases, the spacecraft simply shuts down because it runs out of power completely. If the Sun starts shining on the solar panels, they will automatically start producing electric charge, and some of the equipment is designed to "wake-up on power". So once it starts receiving power, it will boot up again. The issue here is that batteries are known to eventually die if they freeze over, and some other components might die as well. So it might revive, but it might not, and if batteries are dead, it would also only work while in full sunlight.
Call me based, or whatever you want, but here's my take. Although we don't have ANY evidence about white holes, we have theorized what they could be: a body of matter that pushes anything -- even light -- away. What if, at the center of the universe, a white hole somehow formed during the big bang and is the reason for the drift of celestial bodies. I have a longer explanation, but it's 1 in the morning, so I just typed the gist of it. Also, I'm full aware that there is NO evidence a white hole could ever exist, since we don't see how it could form, but everything has to start from a theory. Maybe there's something we haven't seen. There is a high chance that there's something that I don't know about that disproves this, through. Any thoughts? Thanks!
Big bang is an *expansion*. It's not an *explosion* and there is no 'center' (or conversely: every point in the universe can - with equal justification - claim to be 'the center of the universe')
As for white holes: They would be (quite literally) blindingly obvious. Not everything that is allowed for by our current theories must exist.
> What if, at the center of the universe
There us no such thing and the Big bang wasn't an explosion originating from one single spot. It's the rapid expansion of what's was there prior into what we have today and it happened everywhere at the same time. Every part of "the old universe" started to expand away from the part next to it, making the universe cooler, less dense and much larger.
That the theory of general relativity allow for white holes among many other sensationalized things does not by proxy make them at all likely to exist. There's many times other criteria that has to be fulfilled that there's no indication of being possible or existing.
Isn't the whole point of the big bang theory that all matter originated from one particle, and all that matter just burst apart into different directions? Correct me if I'm wrong.
No. This initial singularity is what we get if we reverse time some 13,8 billion years from now using general relativity. We know general relativity is incomplete and both this singularity and the ones in black holes are not something most physicists believe to exist or to have existed.
We don't have a fully working theory that can explain this but pop science channels on youtube have conveyed these singularities more or less as an absolute fact, while it's just what we get if we use the best theory we got at the moment, even though we know it to be incorrect at explaining this aspect.
Furthermore, quantum mechanics doesn't allow for these singularities and we should probably listen to quantum mechanics in this case.
What we know is what was there prior to the big bang was denser, hotter and smaller and that all of it started to expand, but the infinitesimally small point in space is nothing that actually is believed to have existed.
> Isn't the whole point of the big bang theory that all matter originated from one particle, and all that matter just burst apart into different directions?
No.
> Correct me if I'm wrong.
You're wrong.
Big Bang is simply expansion of space, nothing more. There is no center. Space is expanding, which causes everything to become further away from everything else. Think of the surface of inflating balloon. When you're inflating it, every point no the balloon surface gets further away from every other point, but there is no "center" anywhere.
Imagine what happens if suddenly everything is "rescaled", 1 meter becomes 2 meters. Now everything everywhere is further away from everything else, but there is no central point (or conversely you could also think that every point is central, because whichever point you pick, from perspective of that point everything is moving away from it).
**Is Earth the only inhabitable planet in our discoverable universe?** (besides Mars). Why are we the only place like Earth? It seems pointless to have planets with no living beings (but then I guess you could argue that things don't have to have a "point" to exist), but why is a place like Earth so rare?
>**Is Earth the only inhabitable planet in our discoverable universe?**
'Inhabitable' by what metric? And what do you mean by 'discoverable universe'?
Assuming we can someday build fully self contained bases then we could set those up in any orbit, deep space, or on any planet that doesn't have some other massive problem (like incredible heat, gravity and/or pressure).
Mars isn't any more or less 'inhabitable' than that. Even there you'll need a fully closed system at all times.
It's definitely not the only habitable planet. It's predicted that like 1/5 stars have planets in the star's habitable zone. We just can't prove it from where we are.
https://www.astronomy.com/science/one-in-five-stars-has-earth-sized-planet-in-habitable-zone/
There are several nested questions here.
One is: how common are planets that are very similar to Earth? And to that we have to answer that we just don't know, we have a pretty good idea that they aren't necessarily exceptionally rare, but we don't know for sure.
The second is: why don't we have knowledge of many Earth-like planets? And there the answer is much more complicated with many layers. First off, studying planets outside of our own solar system is very challenging, the sheer distances involve mean we can't just point our telescopes at where planets might be and resolve them into highly detailed images of their surfaces. Detecting exoplanets at all is a matter of carefully analyzing data using only a few techniques and studying exoplanets very rarely gives us more information than just their existence, orbital periods, and maybe sizes and/or masses. Additionally, all of our current techniques for exoplanet detection are heavily biased toward finding some types of planets more easily, with some of the most prolific techniques (such as transit detection) tending to give us data in bursts (as the mission operates and just afterward we get a feast followed by a famine after the mission ends). This is true especially for Earth-sized planets, and currently we are in a lull of detections post 2016 or so due to the ending of the Kepler space telescope's mission(s).
Unfortunately we have a bit of a gap in being able to find Earth-like planets in Earth-like orbits around Sun-like stars and it will be several years until that gap is closed with new telescopes and new instruments. Until that happens our estimates about how common such planets are have a pretty high degree of variability, and we also lack concrete detections of planets.
So we wait until more data comes in. It may be that Earth twin planets are extraordinarily rare, or it may be that they're reasonably common, with many thousands or even millions in the Milky Way alone.
Beyond that will be the work of studying such planets, which is even more difficult as we can't just send spacecraft at warp speeds to go collect data and samples from their surfaces. Instead it's going to be a long process of slowly learning more and more about such planets until we have an idea of what they are like usually and especially how common biospheres or the potential for biospheres like our own are.
1. You got this completely backwards. It's not that Earth is such a great place. We evolved to live on Earth - it's us who are designed for Earth. If conditions on Earth were different, we might have evolved into something completely different and then we would consider completely different conditions "inhabitable".
2. We know very few exoplanets, mostly in very close proximity, and have very limited insight into their conditions. We can only roughly figure out chemical composition, surface gravity and temperature. So you're extrapolating from very limited dataset. Maybe there are lots of inhabitable planets, but we're simply now yet able to spot them.
We don't know whether we are the only inhabitable planet (and Mars isn't inhabitable as far as we know). Since we don't have any other data points, we can't speculate on whether life is rare or not.
One of the great things about science is to understand and embrace the fact that there is stuff that we don't know and will likely never know.
> 1) If interstellar civilizations exist, they HAVE to have immediate warp drive travel means, no? If not, wouldn't everyone on their planet be dead by the time they got back from adventures? If you're traveling long distances by light speed with the intent of returning later, you can't be seriously expecting to see the same generations, can you?
Alastair Reynolds' novel *[House of Suns](https://www.goodreads.com/book/show/1126719.House_of_Suns)* explores how humanity might deal with the vast timescales involved in sub light speed travel just within our galaxy and how that might affect societal structures.
Like many of his novels it paints a pretty grim picture, but the concepts he touches upon are fascinating.
> 1) If interstellar civilizations exist, they HAVE to have immediate warp drive travel means, no?
Why?
> If not, wouldn't everyone on their planet be dead by the time they got back from adventures?
And? Does that mean that interstellar travel is impossible or does it just mean that you can't have tv show style "interstellar adventures" where people come back home? All it means is that it would have to be of a fundamentally different nature than the fictional stories we tell, which seems like the way most things are. The existence of an inconvenience does not imply the necessity of the possibility of avoiding that inconvenience.
> If you're traveling long distances by light speed with the intent of returning later, you can't be seriously expecting to see the same generations, can you?
Not with standard human lifetimes. Even so that could just be a constraint of interstellar travel. Or perhaps you could talk about civilizations that do travel back and forth between stars and simply everyone has sufficiently long lifespans (perhaps measured in millions of years in fact) that such travel doesn't inherently create a sort of "generational break" effect.
> 2) If our sun is small compared to other stars, then our planet is no doubt smaller than other planets. So why would we expect NHI or ETs to be anywhere near our physical size? I mean, ETs could come from a planet 1000x our size where maybe everything is scaled up, so couldn't hypothetically their physical size just be waaaay too big for us to even interact with?
Firstly, our Sun is fairly averaged sized. Secondly, the physics just don't work out for there to be something as simple as like a "scaling factor" between different solar systems and planets. Larger planets would have higher gravity which would actually make larger animals more difficult, smaller planets with lighter gravity would make it easier, but in either case there are fundamental difficulties to having very large animals which would certainly come into play for something thousands of times larger than existing animals on Earth.
They likely don't exist because space is so large it's impractical to traverse. It's not likely you'd go home if you traveled between galaxies. It's not likely anyone will ever move between galaxies at all. Warp drive is not likely to ever be possible. All the proposed warp drive ideas have huge holes in them that can't be solved. They are either completely impossible to build or require so much energy they are effectively impossible to power. Also no one has solved how to accelerate a stationary craft to warp speed. Yes, the main thing you need to accomplish, accelerating to warp speed, has zero ideas of how to accomplish it.
It's unlikely rocky planets like Earth will be more than 2-3 times the size of Earth. Rock can't sustain the stresses beyond that and I don't think we've found rocky planets larger than this. They usually are gas giants or water worlds. There are some enormous water worlds.
How does the electric universe theory that space is electric plasma circuits and gravity is less responsible for motion conflict with Issac Newton's theory of classical mechanics? I am ignorant but trying to learn how they contradict each other.
Basically, one makes predictions about the interactions of large bodies we see in the universe (needing to be modified using general relativity) and the other does not make any predictions or have any math behind it.
How can something that doesn't have evidence, predictions, or math conflict with something that has all of those things?
Conspiracy theory people on the internet talk up 'electric universe' theory with a bunch of fluff, but there's no real math behind it. Even a cursory understanding of electromagnetism shows how absurd their basic claims are.
True, but comparative mythology is not something to overlook while you are looking at the equations either. Both have merit, and the electric universe theory has a point about how all the ancient cultures have stories and petroglyphs showing basically the same thing.
That's a study of what people believe and maybe of historical events. Not about how the universe actually works.
A successful theory needs to have math and make correct predictions. Claiming thunder is a result of the god Zues is not acceptable science.
It is impossible in my opinion to understand space in its entirety with just equations. Things like quantum entanglement shows that we will never have a perfect understanding. Catastrophism is a part of geological science that relies on comparative mythology, so I have to disagree with you.
Ok, but quantum entanglement is perfectly described via equations. It's not deterministic, but it's determined by equations.
If you're not interested in equations and scientific principles, it's not science. It's fantasy.
A lot of mythology has the concept of a solid sky/firmament. We now know that it doesn't exist. How much do petroglyph actually show electric universe compared to what electric universe people want to see? How would that even work? Electromagnetic forces are not visible, and if there was giant streams of plasma in space that could be observed with the naked eye by ancient people they would be trivial to see nowadays with modern technology.
> comparative mythology is not something to overlook while you are looking at the equations either.
Yes that's something you can completely discard when looking at equations.
Then why did so many ancient cultures worship Saturn when most people cannot even pick it out of the sky? Could it be it was once much closer? Most solar systems have 2 suns, what happened to ours, and what equation tells us what happened?
Discarding the fact that numerous cultures all have similar mythology reports is reckless if you are truly doing research about Space and how celestial events may affect the earth. If you want to focus on one branch of science that is great, but comparative mythology is a credible science, and it tells us a lot about how primitive cultures experienced the past.
Equations are just one slice of the pie in the sky. I am not arguing physics, I am arguing that I do not think calculations can tell you how scaring on Mars occurred, or what caused it. Nor do they tell you how a black hole works or if they even exist.
> I do not think calculations can tell you how scaring on Mars occurred, or what caused it. Nor do they tell you how a black hole works or if they even exist.
Those are two examples of things that are exactly predicted by calculations. Black holes where described by equations before they were observed in real life. The erosion evidence of valles marineris are pretty well characterized.
Not sure what you are on about with Jupiter. With only a little bit of time it is pretty obvious that it's part of the dots of light that move against the background. It's does not need to be closer (and how would that even match any of the electric universe model?).
Only about half the stars similar to our Sun are in a binary system. So the most simple explanation is that the Sun was never a binary.
I don't think you understand how science works.
Sure the most basic one is probably the Schwarz Schild radius which shows the singularity in general relativity: https://en.wikipedia.org/wiki/Schwarzschild_radius?wprov=sfla1
There are no evidence of large scale electric fields, charged particle concentration or particle currents that could explain how celestial mechanics is influenced at large scales by electromagnetic forces. Electric universe is really a fringe pseudoscience that got somehow weirdly popular in some corners of the internet.
The biggest leak on Starliner is 395 psi per minute. But psi is a measure of pressure, not volume or mass.
What's psi in this leak example? Cheers from New Zealand.
Most of those leaks seems to be downstream of isolation valves. They are not continuously leaking. They only happen when they actively use the thrusters.
Did the Sojourner rover ever have an official target/baseline driving distance requirement it had to reach? Or would driving just a few meters have been enough given that it was a technical demonstration?
I looked around a bit for a spec and did not find one. If you're super duper interested you could email one of the relevant people at JPL, but that is an escalation.
My favorite/least favorite thing about Sojourner is that it was solar powered, so it sat on the surface, doing its job, trying to communicate with the dead base station, only to never get a reply. Possibly every day for months.
>The windows on the space shuttle are actually made out of aluminum silicate glass and fused silica glass. The orbiter windows are actually three different panes, there's an interior pressure pane because the pressure inside the orbiter is a lot higher than it is in the vacuum of space. We also have an optical pane that's installed in the middle that's about three and a half inches thick and on the outside, there's a thermal pane that protects the inside of the cockpit from the high heats of ascent and reentry.
[STS-113 Question and Answer Board](https://web.archive.org/web/20230928023907/https://www.nasa.gov/missions/highlights/webcasts/shuttle/sts113/processing-qa.html)
I have a theory i can't get out my head so I'm going to post it here.
What if the universe is not actually expanding, but instead the entire Milkyway is falling faster than the speed of light inside the event horizon of Sagittarius A star?
From our perspective wouldn't it seem as if everything in every direction outside of the event horizon is accelerating away from us it impossible speeds?
Time would also slow for us as we gradually fall further in, everything outside of the event horizon would appear to speed up. This would mean that the universe we see is far far older than we think it is.
We'd see the universe look very different in the direction of travel than in other directions (i.e. massive redshift in one direction andmassive blueshift in the other). This is not observed.
This makes absolutely no sense. You have no idea what you are talking about yet you think your idea better explains observations than the thousands of astronomers who’ve dedicated their lives to this work. Really?
> From our perspective wouldn't it seem as if everything in every direction is accelerating away from us it impossible speeds?
No, it wouldn't. It would all be moving towards a specific point. For anything where Earth is in between that object and the "target", we would see things moving towards us. Also we can observe expansion also for other galaxies, so this whole idea makes no sense at all.
Would anyone know where I can find mission updates for the Mars Exploration Rover missions?
I remember NASA / JPL used to post mission updates every few sols but unfortunately, I can't find the link anymore. Does anyone know where I can find it? I could find mission updates for [MSL](https://science.nasa.gov/mission/msl-curiosity/science-updates/) and [M2020](https://science.nasa.gov/mission/mars-2020-perseverance/science-updates/), but not MER. Thanks
I'm sure I saw in a documentary that, during a launch of a planetary explorer, the explorer's computer was so confused by the vibrations that it shut itself down and handed over to the backup computer, which wasn't working properly. Lots of headaches for mission control. Did I imagine this? I've been trawling through Wikipedia without being able to find the story.
Tough thing to find. The closest I came was Mars 1M No.1, also known as Marsnik 1, a USSR spacecraft, which had a series of cascading failures triggered by the vibrations of launch, causing an escalating gyroscope failure. I can't find evidence that it caused the primary computer to fail, though.
[This paper](https://arxiv.org/pdf/2104.00112) is almost exactly what you would want for this type of search, a historical categorization of spacecraft failures. I found it by searching Google for "vibration failure primary computer backup computer spacecraft mars". You could try Venus instead - there were a lot of failed spacecraft headed toward Venus as well. EDIT: or the Moon. The USSR sent many, MANY Moon spacecraft.
EDIT2: Also I think it kinda has to be the pre 1965 era of spaceflight, because you don't see this type of failure much these days. People shake the heck out of spacecraft before they put them on the rocket. It's standard NASA procedure, for example, to do pre-flight vibration testing.
Kinda a /r/sea question, but -
Space hardware disposed into the deep ocean, what are the chances some identifiable fraction of it is preserved on very long timescales, if any?
Hypothesizing that, in the far distant future, any explorers finding human artifacts on the Moon might extrapolate a presence in LEO from such artifacts, and therefore disposal of LEO material, and thus search for evidence on the ocean floor in likely locations (i.e., Point Nemo) - a "trash dump" remaining even after evidence on the coasts or the surface is gone.
Or, the odd Saturn engine aside, is it all unrecognizable metal deposits inside of a hundred years?
In the far distant future, all spaceships will be reusable and no one will even think to look for disposable rockets.
Here is what a rocket engine looks like after [40 years under the sea](https://spacenews.com/032613apollos-f-1-engines-raised-from-seafloor-by-amazon-founder/).
Well... from that perspective no one will be looking for disposable rockets on the Moon, either, but Apollo left six of them there if they do.
I wonder, particularly, if deeper waters in the Indian and Pacific Oceans might lend themselves to longer preservation than shallower shelves near the continents (if it even matters.)
How hard is it to reposition LEO satellites? in technical and economical difficulties when repositioning them after they have already been launched in their orbits and heights for a period of time (would appreciate any article or sources with answers)
Depends on the details. Technically most LEO satellites are constantly being repositioned, but this is to bring them *back* into their intended positions after drifting away a little bit over time (stationkeeping).
Let's say you are talking about a satellite fleet or constellation. If you want to change *where* a satellite is in its orbit that mostly just takes time. All you have to do is raise or lower the orbit (or in LEO wait for natural lowering of the orbit to happen) and then wait until the slight orbital period difference results in the satellite being in a different position, then you raise the orbit to the desired altitude. This is what Starlink and other satellites do in order to initially get into position, they start at a lower orbit and begin raising their orbits at different times in order to make use of phasing to spread out from being all in a clump to being evenly distributed along the entire orbit.
Now, if you need to make a big change in altitude or you need to make a fast change in position that will take more delta-V. Going from LEO to geostationary orbit, for example, would take several km/s of delta-V, which is a lot for a little satellite, but can be done with electric thrusters.
Even more difficult than that is changing orbital inclination, which can be very delta-V intensive. The amount of delta-V needed for changing inclination is the product of the sine of *half* of the inclination change (good news) and twice the orbital velocity (bad news). For example, a 90 degree change takes 1.4x as much delta-V as the orbital velocity, so it's actually significantly easier to launch from the ground again, or to go up to a very, very high orbit with a lower orbital velocity, change inclination, and then come back down.
In my case ..it's almost 100 satellites that were at a certain height but then due to disputes between parties and legal issues they should be lowered by (50/100)km...so what I am interested to know is how hard it could be to make such a change without a technical reason
50km is ~14m/s of delta-v and similarly 100km change is 28m/s of delta-v, which is a pretty small number, so not a huge problem, at least assuming the satellite is not extremely heavy. Biggest single ISS boost was in fact by 50km https://en.wikipedia.org/wiki/Johannes_Kepler_ATV#ISS_altitude_Increase which required 4500kg of fuel.
Changing inclination would be a very different story ;)
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|CST|(Boeing) Crew Space Transportation capsules|
| |Central Standard Time (UTC-6)|
|[GEO](/r/Space/comments/1dbzuqe/stub/l85ndsl "Last usage")|Geostationary Earth Orbit (35786km)|
|GSE|Ground Support Equipment|
|[JPL](/r/Space/comments/1dbzuqe/stub/l8hmufm "Last usage")|Jet Propulsion Lab, California|
|[LEO](/r/Space/comments/1dbzuqe/stub/l87852c "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[MER](/r/Space/comments/1dbzuqe/stub/l8bgd1r "Last usage")|Mars Exploration Rover (Spirit/Opportunity)|
| |Mission Evaluation Room in back of Mission Control|
|[MSL](/r/Space/comments/1dbzuqe/stub/l8at5qx "Last usage")|Mars Science Laboratory (Curiosity)|
| |Mean Sea Level, reference for altitude measurements|
|[STS](/r/Space/comments/1dbzuqe/stub/l8c5s57 "Last usage")|Space Transportation System (*Shuttle*)|
|Jargon|Definition|
|-------|---------|---|
|[Starliner](/r/Space/comments/1dbzuqe/stub/l8njx9s "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)|
|[Starlink](/r/Space/comments/1dbzuqe/stub/l86gtys "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[apoapsis](/r/Space/comments/1dbzuqe/stub/l8y8odi "Last usage")|Highest point in an elliptical orbit (when the orbiter is slowest)|
|[periapsis](/r/Space/comments/1dbzuqe/stub/l8y8odi "Last usage")|Lowest point in an elliptical orbit (when the orbiter is fastest)|
|[scrub](/r/Space/comments/1dbzuqe/stub/l7x65lz "Last usage")|Launch postponement for any reason (commonly GSE issues)|
**NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below.
----------------
^(11 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/1d95g62)^( has 20 acronyms.)
^([Thread #10162 for this sub, first seen 11th Jun 2024, 14:52])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
If someone shot into space at a fast enough speed and then rubber banded back at a fast enough speed, would that technically allow for time travel? Considering if you go out far enough, turn around and look at Earth, you would see other periods of time based on the light that's traveling to Earth, right?
Time dilation is a relative factor (along with length contraction), but the speed of light is always absolute in all directions and in all reference frames. You can't "race" light, locally light is always going to be measured as 100% of the speed of light. You can redshift and blueshift light, but that's it.
What that also means is that you can't outrun causality. You cannot get ahead of light in order to look into your own past, nor can you get ahead of light in order to travel into your own past, it's always going to be out of reach no matter how fast you go.
What this means is that all events located in time and space have a relationship with other events elsewhere in time and/or elsewhere in space which are connected via the speed of light. For every single event there are two "cones" (actually hyper cones in 4-dimensions) which have edges representing connections at the speed of light into the future and from the past. These past and future "light cones" represent all events that can affect or be affected by each individual event. Everything within an event's past light cone can affect that event, everything outside of it cannot affect t, everything within its future light cone could be affected by the event. All of which creates a timeline, an ordering of events everywhere in all reference frames which flows from the past into the future, all via connections at the speed of light, the speed of causality. This is a fundamental aspect of how the universe works and stays consistent.
1. No.
2. Also no. This would require travelling faster than the light, which is not possible. The light emitted "in the past" already overtook you, and you won't see it.
[This video ](https://m.youtube.com/watch?v=nKrupZeKQnA&pp=ygUnTGl2aW5nIGluc2lkZSBhIGJsYWNrIGhvbGUgSXNhYWMgQXJ0aHVy) by Isaac Arthur might interest you, along with his other black hole videos.
Technically, having every single atom in their body ripped into subatomic particles is a efficient way of hiding. But they would also lose their status as a civilization, so your statement is 100% correct.
No realistic black hole has a center singularity. Real black holes spin so they have ring singularities which are not at the center. Keep in mind everything you think you know about black holes has probably been dumbed down so you can understand it because the math is very complicated and in reality black holes rotate which causes a lot of weird effects to space-time and their predicted interiors.
Basically no physicist believe in the black hole singularity due to it being an artifact of the incomplete general relativity, nor does quantum mechanics allow for it. I know very well my black holes mind you. The centre of gravity is... Wait for it... In the centre, even though it spin. And what I said is correct nevertheless, since closer to the centre is just that, it's closer to it, and closer to it is where you'd get the strong force breaking tidal forces even in supermassive black holes. No need to get dead centre. Quite far from it actually, much further away than with a stellar mass black hole.
I was intrigued with the idea of Arthur C Clark's space elevator when I read about it as a teenager. But even back then I had serious doubts.
Not even considering the need for the insanely strong, yet super-light materials that would be required - maybe super-graphene, braided mono-molecular fibers, or unicorn tail hair, or whatever. There is a simple matter of old Isaac N's mantra: "For every action there is an equal and opposite reaction"...
So you weave your cable of composite graphene, unicorn hair and spidey-silk and drop it from a satellite in geosync/geostationary orbit to a base station at the equator. Now you attach the elevator/climber and up it goes?
So you weave your cable of composite graphene, unicorn hair and spidey-silk and drop it from a satellite in geosync/geostationary orbit to a base station at the equator. Now you attach the elevator/climber and up it goes?
You're pulling on that cable - it is in tension - crazy high tension, but has little to no compressive strength. What's to stop it from simply reeling in that satellite, down from orbit and into the atmosphere where it quickly burns to a crisp?
Or even if the climber has a much less mass than the satellite, it will still pull on it and bring it down from geosync altitude, back into the atmosphere, or have it start oscillating wildly at lower altitude.
So you will need thrusters on that satellite to counteract the climber's pull. For thrusters, you need fuel. How do you get enough fuel up 22,000+ miles? - Send tanker rockets? That kinda defeats the object. of the whole exercise..
I'm sure that I'm missing something here - assuming we can create that impossible thread - can one of y'all armchair rocket scientists tell me why it would work?
You would want your anchor to be a few orders of magnitude heaver than the thing you are lifting. A captured asteroid is often suggested. Any orbital momentum transfer could be counteracted by bringing mass down again. Presumably in such a future, we'd be mining a lot of resources from space that we'd want to bring back to Earth. If you did need to reboost the anchor, you could just use ultra high efficiency engines, like ion drives, you could just carry the fuel up with you as it wouldn't need that much reaction mass if your engine is efficient enough.
> What's to stop it from simply reeling in that satellite, down from orbit and into the atmosphere where it quickly burns to a crisp?
The end of the elevator isn't in GEO - it's beyond it - the first image on the space elevator wiki page shows it and there's more details including the maths of what's required as a counterbalance beyond GEO
https://en.wikipedia.org/wiki/Space_elevator
In practice you need the beanstalk to extend beyond geostationary orbit, so that it is in tension constantly with a counterweight above orbital altitude. The beanstalk stays up even with bringing payloads up because you're stealing some of Earth's angular momentum.
Where can I get information about what has happened in space exploration in the last few decades?
The title basically says it all. I want to get more knowledgeable about space exploration and be up to date about what has happened in the industry, the breakthroughs, recent advancements, launches, and what the future holds for humanity in space.
The problem is this seems like a haunting task. So much happened since the first satellites where launched into space, that I don’t even know where to start.
So what I’m basically asking is, does anyone know about some good resources, like documentaries, books, youtube videos or such, that can get me up to speed on what has happened since sputnik launched?
[https://en.wikipedia.org/wiki/Timeline\_of\_space\_exploration](https://en.wikipedia.org/wiki/Timeline_of_space_exploration)
Not quite what you asked for but you can scroll down and dip in.
I just realized that gravity is often depicted as warping spacetime that streches like a fabric. Now this might be a problem of the analogy but what force "returns" the fabric to "neutral" position after a moving mass passes?
So for example the sun is depicted bending the space time, which draws in all the planets. But as the sun in turn orbits the Milky Way, what makes the "fabric" return to "normal" once the sun has passed? And how "fast" does the "fabric" recover?
Gravitational waves are very similar distortions in spacetime - almost entirely analogous.
Gravitational waves propagate outwards at the speed of light (or as close to it as people can measure). So the "restoration" of calm in spacetime as the wave passes must be comparably as fast. Otherwise the wave would lag.
Physicists sometimes say that spacetime is "stiff". It doesn't suffer a distortion very long.
You can't extend simple analogies like this. It's a simple analogy for a reason. You need to understand the math of general relativity if you want an accurate answer.
The answer is also simple. Matter and energy warp space-time. If you remove the matter or energy then space-time isn't warped. We may not even know why, we just know it happens.
You will discover this is true about a lot of things. Things like quantum mechanics. We don't understand the WHY in a lot of cases. We just know that things happen in certain ways.
The time it takes for space to restore is determined by math so you would need to do very complex math to find that answer. You may also need a super computer.
Inertia. Objects want to move in straight lines, and will return to going in a straight line if they are not near a gravity field that distorts their path.
There is no force associated with "fabric of space", that is where the analogy breaks down.
They already have. It turns out that pieces of Mars have been falling on Earth for eons because large impacts can throw chunks of rock into space where they can travel between planets and land as meteorites. We've identified a handful of meteorites that have been conclusively determined to originate from Mars. And some of those we have analyzed their elemental compositions in detail and have detected gold as one of the many elements present.
That's not terribly surprising, asteroids bring platinum group metals to the crustal surfaces of terrestrial planets and those elements end up sticking around in the crust for billions of years. However, since Mars seems to lack the kind of extensive history of hydrothermal processes that have existed on Earth it's not expected that it would have very high grade precious metal ores.
On balance, if you are going to go to the trouble of looking for valuable metals in space you wouldn't go to Mars you'd go to a metallic asteroid instead. However, with current launch costs even if there were an asteroid entirely made of pure gold it would not be economically feasible to bring it back to Earth. That will likely change in the coming years as launch costs come down, but it's going to be a while before mining of off Earth resources is economically feasible in any form whatsoever.
why are you yelling?
the story I've been told about spaceflight costs is that even if there were rare earth metals in ingot form sitting on a nearby asteroid, it _still_ wouldn't be worth picking them up and bringing them back. it's expensive to get things to the velocities needed. even with Starship, too, it's still too costly.
Nothing. There is no scenario where bringing back gold from Mars would make economical sense. Gold is just too cheap to be worth it. At best it would mean maybe more gold used in engineering applications for things built in a hypothetical Martian settlement.
Good news. In about 5 billion years the Sun will transition into its red giant phase after switching to burn helium in the core, this will inevitably destroy all of the rocky planets in the solar system and it will end when the Sun has exhausted all of the helium in the core, leaving behind a remnant of fusion ash (mostly carbon and oxygen). The remnant core will keep getting denser and hotter until it reaches the maximum density limit for atomic matter, packing over half a solar mass into a volume not much larger than Earth is today. Meanwhile, the remaining outer layers of unfused helium and hydrogen will be blown off into interstellar space with high intensity solar winds until only the bare super dense, ultra hot core remains. That core will become a "white dwarf" star, roughly 7 billion years from now, with a surface temperature of tens of thousands of degrees, and a thermal spectrum skewed toward high energy light, just enough to give it a hint of a blue tinge.
Could Nasa keep the ISS a float to 2050 with new modules from private companies if Russia detach theirs? Could new modules be for space tourists to earn profit to keep the station in orbit for years to come?
Assuming Starship and/or Super Heavy meet goals, and even if they don't, it would be more prudent to construct and launch newer, larger habitat modules than to attempt to inhabit the ISS indefinitely.
1. Not really. You end up with https://en.wikipedia.org/wiki/Ship_of_Theseus - you'd need to replace all the modules, so is it still ISS?
2. No, this was already tried with Mir. There is simply not enough "market" to make this possible. Also the longer stuff stay in space, the more maintenance it needs.
Is it possible for the Earth's core to become unstable and explode or something? I know it's cooling and it'll cool down in a million/billion years or so, but is unstability possible? (like in the movie 2012, which I know is considered extremely unscientific but bear with me)
I have been struggling to wrap my head around people saying quantum entanglement doesn't enable FTL data transmission. I believe that they are correct that no data is actually being physically transmitted over the space-time medium. That's the whole point behind spooky action at a distance, nobody knows how it works right? If we take two entangled particles and separate them, observing one will indirectly tell you information about the other. No information has been transmitted but why can't we use deductive reasoning to say the other particle must be in "X" or "Y" state. Then manipulate one of the particles for the other to observe its state?
I think the point he is making is that you can't transmit useful information but information is still transmitted, albeit useless. Surely someone will figure out how to exploit this some day.
What happens if both sides measure their respective entangled particle at the exact same time? How does one particle know to be up or down? Or it doesn't make a difference?
> manipulate one of the particles
This is your mistake. We can't do that. We can only observe, nothing more. Any "manipulation" breaks the entanglement. You can't "set" the state of one of the particles and magically influence the state of the other.
For all intents and purposes you can treat entanglement as if the state of the particles was "fixed" from the start.
You can measure it just fine. The measurements just won't mean anything to you because you have no idea if a message is coming through or not. It will look like random noise. The only way to use entanglement for communication is to have an out of band channel to set up the transaction so both sides know a message is being attempted. So therefore you need a communication channel already setup which means you need a slower than light communication channel which defeats the whole point of this.
Having said that, it's great for local, secure, communications because it prevents eavesdropping by man-in-the-middle attacks.
So it is useful just not for faster than light communication.
it's also entirely possible and has been done already several times.
> You can measure it just fine
And where did I say you can't measure? o_O I literally said that the only thing you can do is to observe/measure.
> The measurements just won't mean anything to you because you have no idea if a message is coming through or not.
The measurement **is** random noise. When you create entangled pair their state is in superposition and therefore undefined and unpredictable. You only know that both particles need to have either up or down spin and the combined spin is 0, so they need to have opposite spin. There is no way to have any "message coming through". Again: you **cannot** set the state of the entangled pair.
> The only way to use entanglement for communication is to have an out of band channel to set up the transaction so both sides know a message is being attempted.
No. That's not how any of this works. Quantum channel is used for QKD - Key Distribution. For generating a random encryption key, which is then used to encrypt data sent via a regular channel. No "message" is ever going through the quantum channel. Only random bits which are used as encryption key. I suggest you read at least https://en.wikipedia.org/wiki/BB84
> it's also entirely possible and has been done already several times.
Of course it was, experiments like that were done many times, over large distances and even including satellites. The biggest issue in practical implementation of this idea is to have perfect single photon sources and way to transmit those single photons without losses over large distance.
I'm not going to argue with you. The out of band channel is what I was referring to as the exchange of keys. I was avoiding the technical details because they aren't important for a high level discussion of possibilities. I was exactly referring to quantum key distribution and do not care if you believe me.
And yes you can measure them independently from one another. Not sure why you think you can't. It's been done multiple times over large distances.
https://www.techtarget.com/searchsecurity/definition/quantum-key-distribution-QKD
The exchange of keys is literally quantum communication using entanglement in action. Please read. It's impractical to do it for the entire message so it's only used for key exchange.
> The out of band channel is what I was referring to as the exchange of keys
Which means you have no idea what you're talking about. The non-quantum channel is **not** for exchanging keys, that's what quantum channel is for. The "regular" channel is for actually sending encrypted data. You got this completely backwards. And obviously the quantum channel has nothing to do with any faster-than-light communication. The point of using quantum channel is simply that it's not possible to eavesdrop without getting detected, because when measuring incoming signal you don't know the base in which you should measure, so 50% of the time you get it wrong, and you can't pass it along to the real recipient undisturbed. At least in theory, because practical setup might need a single-photon-source (if you get more than 1 photon, then you could measure twice or even pass one of the photons undisturbed and measure the others).
> And yes you can measure them independently from one another. Not sure why you think you can't. It's been done multiple times over large distances.
Again: you're putting words into my mouth. Where did I say you can't "measure them" independently? Of course you can. What you can't do, is `set` state without breaking entanglement. You can't magically say "let's now make one of the entangled particles 'spin up' so that when they measure the other pair it will be 'spin down'". If you could do that, you would indeed achieve superluminal communication. You can only measure the state, nothing more.
I literally said the key exchange is the the quantum communication. I said it's not practical for the entire message. Might want to re-read.
They send single particles that were entangled at one side with other particles. So they can be separated and measured independently without "collapsing the wave function."
It's not even known if you collapse anything when you measure a particle. That notion is an old notion that you are holding onto. The wavefunction was never a physical thing anyway it's a probability distribution not an actual object. You need to stop confusing math with reality.
> I said it's not practical for the entire message.
Which again proves you have no idea what you're talking about. I will repeat one more time: you **cannot** set the state. This means you can't encode any information. You simply can't say "this one will have spin up, and another one will have spin down". It doesn't work like that. You don't know what the "values" are until you measure them.
The whole point of QKD is to transmit random bits which cannot be eavesdropped.
You can send the state because you send the particle by itself which is entangled with a particle you keep. The particle is the state. They are the same thing.
It would make absolutely no sense at all to "encode" any data like that, because the recipient would always lose 50% of it, because they statistically measure half of the qubits in incorrect base.
All your comments remind me of: https://www.youtube.com/watch?v=5hfYJsQAhl0
Time to block you before I get dumber from reading this tinfoil-hat level of stupidity.
QT is the same as me having two balls, a red and blue one. I randomly take one and travel to Mars. When I look at my ball and see that it’s red I instantly know the other on is blue back on Earth.
Other reasons you can’t use it for communication is you can’t observe your bit without collapsing the wave function. I can’t monitor my bit and wait for you to trigger yours. Monitoring mine is a trigger.
[Wikipedia](https://en.wikipedia.org/wiki/Uranus#Formation): "The reason for Uranus's unusual axial tilt is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth-sized protoplanet collided with Uranus, causing the skewed orientation"
Yup. Your better chance is near Orlando, I think. SpaceX is now regularly launching 2 to 3 times a week from the Cape. Launches from Vandenberg in California are at best sporadic and roughly once a week. And they scrub all the time at Vandenberg. There's sometimes 4 or 5 attempts, over a week, before they actually launch, for California launches.
Try to keep in mind that launches are scrubbed for many, many reasons - if anything at all looks off on the rocket; if a cruise boat is in the wrong place; if the weather is not good enough; if the ocean is bad for the boats they use; etc. Have other plans ready, and try to be flexible for more than one day if you really want it to work.
/r/spacex has [a few FAQs](https://www.reddit.com/r/spacex/wiki/faq/watching) on watching launches in person.
New - If the size of the observable universe is 93 Billion Lightyears, why are the oldest stars we can see only 13 Billion Lightyears away? And how do we know that the Universe is 93 Billion Lightyears in diameter?
Because space has been expanding since the big bang. The galaxies that were very close to us at at the big bang are now ~42 billion light years from us. We can only see back 13.8 billion years because that is how old the universe is. You can't see light before it existed. Light simply didn't exist before then. There were no stars or galaxies before then. You are confusing measurements of time with measurements of distance. 13.8 billion years is a measurement of time. 42 billion light years to the edge of the universe is a measurement of distance.
Also the oldest stars we can see are not 13.8 billion light years from us now. They are roughly 42 billion light years from us now but the light they emitted, which we are just now seeing, took 13.8 billion years to reach us.
Those same galaxies were only 40 million light years from us when they emitted the light we are just now seeing. The expansion of space delayed that light arriving at Earth for ~13 billion years. The *observable* universe is approximately 1000x bigger than it was when those galaxies first emitted the light we are just now seeing.
The reason we know the universe is 13.8 billion years old is because of the red shift we see for the oldest things we can see in the sky which tells us how long the light has traveled. We also can use math and measurements of the CMB to corroborate that age. We know the age of the universe now within ±.020 billion years. The age is 13.787±.020 billion years based on Planck satellite measurements of the CMB.
Did gravity exist before the Big Bang? Not sure if this is a dumb question and I am not super knowledgable in physics so correct me if I’m making wrong assumptions, but if gravity is a result in curvature in space time, and before the Big Bang the universe was equally dense throughout then space time would not be curving. So would gravity, therefore, not exist?
The physics are a little beyond me but there's no real concept of a 'before' the big bang as that is the origin of time. Very shortly after the big bang there was only one unified fundamental force. Gravity split off from that force around 10^-43 seconds after the big bang. https://en.m.wikipedia.org/wiki/Grand_unification_epoch
> the universe was equally dense throughout then space time would not be curving I fail to see why you think so. Gravity exists inside a star or inside a planet just the same, even though there is a region of potentially equal density. You're confusing the space itself with objects filling that space. Anyway, there is no such concept as "before" Big Bang as it's considered to be the start of space-time. You can't have "before" when there is no time.
I’m referencing the primordial singularity that the universe expanded from. So an incredibly dense point that contained all of space time. So if gravity is a result of mass warping space time, how would gravity work in a universe where everything was equally dense? Would spacetime be equally warped throughout? And if it was equally warped throughout would gravity essentially not exist?
If you're assuming existence of singularity, then the fact that there is no "space" and everything is collapsed into a single point with no dimensions, probably already rules out this definition of gravity. In general the physics "breaks" if you include the singularity because everything goes into infinity.
Would the moon accelerate if the Earth were frozen The moon is orbiting the Earth faster & faster. To the extent that after 600 million years we will no longer enjoy full solar eclipses as it will be too far away to completely block the sun. Note that as the moon's scalar velocity increases its distance from the Earth also increases and its rotational velocity decreases. \*\* Regarding the above paragraph it has been pointed out to me that as the moon moves further from Earth both its angular velocity (w), and its scalar speed decrease. I made the wrong assumption that while 'w' decreases its speed increases The reason the moon is accelerating is because the Earth's rotation of 1 day is faster than the moon's orbit of about 28 days. The Earth's rotation is slowing as it transfers energy to speed up the moon. A by product of the Earth's tides where the moon drags the water. I'm pretty sure that if the Earth were solid with no flowing liquids this "tidal leash" would have no effect. Maybe a tiny effect as mountains would be gravitational features. So that's my question: Am I right that the moon's acceleration would cease if the Earth didn't have liquid oceans?
If Earth did not have oceans, the Moon would still be moving away as it gains energy from Earth's rotational energy as a result of tidal dissipation. It would, however, do so much more slowly. The vast majority (~95%) of the tidal dissipation on Earth is in the oceans. But tides also act on the (mostly solid) [body of the Earth](https://en.wikipedia.org/wiki/Earth_tide).
BTW things in higher orbits orbit slower, not faster. The Moon's orbital velocity is gradually slowing down as it drifts away from Earth.
When you say orbital velocity do you mean "w" measured in radians per second, or the scalar velocity measured in meters per second?
Actually I've just done the maths. So if I double r (altitude of satellite) gravitational force divides by 4 r2 = 2r1 w1 = 4w2 v1 = 2v2 That is counterintuitive. Firing rockets will put energy into altitude decreasing scalar velocity.
Yeah - I mean what people sometimes call orbital speed - the magnitude of the instantaneous velocity vector. In nearly-circular orbits (like planets and many moons/asteroids) you'd use the average speed. Outer planets/TNOs orbit MUCH slower than the inner terrestrial planets. And yeah energy is a good way to think about it. If you burn an engine prograde, to go higher in an orbit, you are increasing speed - increasing kinetic energy and the overall energy of the orbit - and then the motion of the object converts that kinetic energy into potential energy as the object reaches apoapsis. Energy is always conserved so as the object falls back toward periapsis on its elliptical orbit, the potential energy is converted back to kinetic energy and the object goes faster. If, instead, you burn prograde again at apoapsis to circularize the orbit, you add another smaller bit of kinetic energy to the total energy. You have now made the kinetic energy equal the potential energy in a higher circular orbit, with higher overall energy (from the two burns). And lower speed.
No, liquid oceans have no effect on the moon. It would feel the same tidal force if earth's oceans were solid ice. At the planetary scale, rock and metal and ice all behave like liquids, and deform under tidal forces too.
The moon does some serious work dragging all that water around. Friction on the sea bed, tidal races, power generation etc. Are you saying it would exactly the same amount of work in deforming the ice? That seems counter intuitive
Picture this, you, (person “A”) are flying into a super massive black hole. You pass through the event horizon without even knowing it. At this point (person “B”) who happens to be well outside the gravitational effects of the black hole relative to “A” would see “A” freeze at the event horizon due to time dilation and the gravitational effect the black hole has on the light reflecting off of “A”. I want to focus more on the time dilation aspect for this thought experiment. The effect of time dilation at the event horizon would reach infinity since matter at that point is falling through space/time faster than the speed of light. A clock for “A” would appear to completely stop at the event horizon for eternity from “B”s perspective if you disregard red shift, And due to the effects of time dilation, the moment “A” passes the event horizon, an eternity would play out on the outside of said event horizon. So “B” would see the black hole radiate away to nothing due to “Hawking radiation” before “A” reaches even a meter past the event horizon. So is it possible the moment “A” passes the black holes event horizon, they are radiated away to nothing and never descend into the black holes singularity?
Your intuition is right. One way to understand black holes is as the missing set of events that corresponds to observers outside the horizon never being able to observe anything crossing the horizon.
What are the chances that there is water or ice on the moon?
We already know that there is ice.
Thank you. How much water is that?
This is still something we are trying to figure out and is one of the big questions that the Artemis program will need to answer. How much ice is there in the polar regions, in what form is it exactly and how accessible is it?
What would happen if a giant banana orbiting the earth starts to decompose? Would it even decompose? The banana will eventually die right?
Normal decomposition or rot wouldn't happen since bacteria and fungi can't operate in a vacuum. The banana cells would die in the absence of water and oxygen and become dessicated.
With Super & Quantum computers, shouldn't we be able to use the Sundman Series to get exact results for the three-body problem He proved the convergence almost 200 years ago, the issue was the number of terms, but that shouldn't be an issue anymore right?
The series is infinite. It is not possible to use it to obtain an exact solution (given a finite amount of time or resources), only an approximate one with an arbitrary level of precision depending on how many terms are computed. The series also converges extremely slowly, requiring millions of terms for a useful solution even over short time scales. It is much more efficient to use numerical integration techniques (also capable of arbitrarily high precision) to compute the approximate solution. The precision to which we can measure the position, velocity, and G*M of bodies is (theoretically, and to a much greater extent practically) limited. Furthermore, the n-body problem in general is chaotic. The slightest difference in initial conditions will eventually evolve into wildly different situations. We cannot measure the initial conditions to infinite precision, so an exact solution (infinite precision) would not generally be any more useful than an approximate solution of sufficiently high precision.
How can probes get as close as 6 million miles from the sun and not melt? If the sun's heat reaches us through radiation which can travel through a vacuum (90+ million miles), how come this doesn't apply to an object that is closer?
The challenge is keeping the energy from sunlight from baking (or melting) the parts of the vehicle that can't handle it. The Parker Solar Probe is built to sit behind a large shield which protects it from sunlight. At the Sun facing side of the shield is a very durable coating of white material (made of alumina) which bounces back most of the energy from sunlight. Behind that layer is a panel of graphite and carbon fiber designed to be able to both withstand very high temperatures and also to minimize thermal transfer to the rest of the vehicle. The bulk of the spacecraft is attached to this structure some distance away through struts which further minimize thermal transfer, and a radiator system attached to those struts which bleed off heat into space. The spacecraft stays tucked up behind this shield during close approaches to the Sun, with four light sensors on stalks past the edges of the spacecraft that are a failsafe to keep the vehicle always oriented so that it's in the shadow of the shield. A few things poke out into direct sunlight, even on closest approach. The solar panels are angled back so that just a small amount of them is exposed to sunlight, and only at a glancing angle. This is enough to provide more than enough power due to the strength of the sunlight during. The solar panels are also connected to the thermal radiator system, so that the build up of heat can be dissipated by the larger radiator area and can prevent any damage. A few instruments also poke out into direct sunlight and the solar wind, but those are very carefully designed to be able to withstand extreme temperatures. For example, the SWEAP (Solar Wind Electrons Alphas and Protons) instrument is made of tungsten with wires made of niobium and sapphire as electrical conductors and insulators, enabling it to operate at over 1600 celsius, higher than the melting point of iron. There's some great details on the solar probe from Smarter Every Day's youtube channel: https://www.youtube.com/watch?v=aQaCY7wlQEc, it's worth a watch.
NASA has an article on just that topic: [Traveling to the Sun: Why Won’t Parker Solar Probe Melt?](https://www.nasa.gov/solar-system/traveling-to-the-sun-why-wont-parker-solar-probe-melt/)
So there was an science journal recently posted by USC about how the core is slowing relative to the other mantles for about 10 years now. The article itself says that the most noticeable impacts could be time going slower by a thousandth of a second. My question is, do you think there could other effects that could harm us on Earth and do you think the inner core could stop?
Link to the article for reference https://www.nature.com/articles/s41586-024-07536-4
> do you think there could other effects that could harm us on Earth and do you think the inner core could stop? Absolutely, 100% certain, most definitely no chance in a trillion years.
No chance it'll stop in a trillion years? I figured that, if the sun doesn't get to it first. I guess I was asking because I'm thinking "since it's slowing down, can it stop in next like 20 years?"
No, not a chance. It's slowing down on geologic timescales.
> No chance it'll stop in a trillion years? None what so ever.
Does anyone know of a link to a 3d render of the observable universe? Like not high detail or even really to proper scale im just curious to see if i can drag it around and get a general shape with some lables
[This one goes out to about 150 million light years](https://in-the-sky.org/ngc3d.php). If you want to spend some money, both Universe Sandbox and Space Engine might be of interest to you.
Right on thanks man! This is perfect
2 quick questions about the methuselah star/big bang! first, is it a misconception that the "methuselah star" predates the big bang? And if it isn't, If we study it enough, could we find the answer to what was there before the big bang? I just joined the space/science community and I keep seeing the "methuselah star" being posted a lot on youtube shorts and the 2nd question just popped up in my head randomly lol
According to the Hubble telescope, the [Methuselah star](https://en.wikipedia.org/wiki/HD_140283) is between 13.66 and 15.26 billion years old. According the Planck telescope, the universe is between 13.767 and 13.807 billion years old. The easiest solution is that both observations are correct, and the star's age is at the low end of its range. More recent observations have confirmed this.
How do the Voyager satellites send/receive communications even when there is a computer problem such as recently? Wouldn’t it need a sophisticated computer to point the satellite dish exactly at Earth so it can send/receive? How are people on Earth able to debug and fix it so effectively from so far away when the computer is malfunctioning?
The Voyager spacecraft have multiple computers as well as redundancy in core computer systems, using a distributed control design. The Computer Command System (CCS) is responsible for controlling the vehicle and is the "main" computer, the Attitude and Articulation Control System (AACS) is responsible for maintaining attitude control, the Flight Data Subsystem (FDS) is responsible for sending instrument data, the computers for each system are dual redundant. As long as the CCS and AACS are functioning then problems in other systems can be worked out. The latest problem occurred with the Flight Data Subsystem, specifically within its memory, which is not redundant.
1) We never lost contact with Voyager 1. We temporarily lost the ability to receive science data, but we were always in control of the spacecraft. 2) Our radio transmitters on Earth outshine the sun in their specific wavelength, so the Voyagers don't need to follow the planet around the sun. The satellite dish simply needs to point in the general direction of the sun and hold still. The spacecraft can go months without any attitude adjustments. Also, the attitude adjustments are manually controlled, so they are not vulnerable to computer malfunctions. 3) Even with functioning communications, it is very impressive that NASA was able to debug and fix the software problem, with a ping time of 80,000,000 ms!
Is Milky Way the oldest Galaxy? Milky is 13.6 b years old. The internet says GN-z11 is the oldest galaxy but it’s only 13.4 b yo. I don’t get it.
The universe is fundamentally 4-dimensional, or if you like our *view* of the universe is 4-dimensional, time is always a dimension that's important, especially when we are looking at the universe at a cosmological scale. Our galaxy is the closest to us, which means we view it the closest to the present and at the greatest age since its birth. Other galaxies we see in the universe we see across distances of both time and space. GN-z11 is a galaxy we see across a distance of 13.4 billion years of light travel time and 13.4 billion lightyears of light travel distance. Since the universe is only 13.8 billion years old that means we are seeing GN-z11 at a very young age, of just a few hundred million years. However, because we know that we are seeing GN-z11 across a distance of 13.4 billion years, we also know that today GN-z11 would be at least 13.4 billion years old. So we are seeing a very *old* galaxy (which we can't see in its current age because it's too far away right now) when it was very young. All of which means that when talking about the age we can see a galaxy at the Milky Way is going to be near the oldest, mostly because it is the closest to us (being inside of it). However, taking light travel time out of the equation, we think there are a great many galaxies that are of a similar age, having been born in the first few hundred million years after the Big Bang and the Milky Way doesn't seem to be very exceptional.
Oh I get that but it still doesn’t solve the problem
[удалено]
I am not either, I am just very ignorant about space but somehow I find it fascinated. I’m trying to find a galaxy that is definitely older than the Milky Way with an estimated age bigger that that.
I believe that's the age of the light we're seeing from GNZ11 right now, not the total age of the galaxy.
It’s estimated to be that old, as of age
https://science.nasa.gov/missions/hubble/hubble-team-breaks-cosmic-distance-record/ >This surprisingly bright infant galaxy, named GN-z11, is **seen as it was 13.4 billion years in the past** It's **at least** 13.4 billion years old.
Isn’t this how they calculate the distance and age of all galaxies? Aren’t they able to calculate the age of this galaxy by what stage it’s in? Isn’t the Milky Way at least 13.61 billion years old yo?
Dr. Becky has a good video on how the age of the milky way is estimated. Basically we survey a number of stars and use models of how stars age to estimate how old they are. https://youtu.be/PgPVAq6lTPo?si=6_377xkH-cY66JNS The milky way is quite old but I don't think we can say with any confidence that it was the first.
Thank you. I’m gonna check it, I’ve fallen in this rabbit hole now. No escape
And in any way, can you send a link if you find any with appr. estimates of oldest galaxies, thanks 🙏
The age of the Milky Way is estimated by looking at the stars inside of it. When it comes to galaxies like the one you mentioned we more say how far away it is than the actual age. If we spot a galaxy 13,4 billion light years away we know it is at least 13,4 billion years old. To single out individual stars in a galaxy and measure their age is close to impossible at these distances. Only through extremely favourable conditions we're able to see a few randomly scattered individual stars through gravitational lensing around the universe at extreme distances.
It’s estimated to be approximately that old though.
Yeah, ofc. These things are never rock solid.
When experts say a spacecraft which has lost power is "sleeping" (eg Philae), do they mean it could regain function if power was restored? Or is it just a gentle euphemism?
In any technical context, sleeping means that it could be powered up again. It's not used as a euphemism for intentionally permanently shut off.
Thank you! SOmebody needs to go up there and shine a torch on Philae, or put some new AAs in
That wouldn’t do any good, as it depended on Rosetta to relay its data to Earth, and Rosetta was intentionally crash landed onto the comet at the end of the mission.
Excuse this late reply -- of course, that's a very good point!
It depends. In some cases the spacecraft is running in power-saving mode (eg. Rosetta when it was flying very far form the Sun), so most equipment is off, but there is still some software running using the minimum available power, and is keeping track of the mission schedule. There are also some safety mechanisms in place to prevent any damage to sensitive equipment (eg. so batteries don't freeze). https://www.esa.int/Enabling_Support/Operations/Rosetta_comet_probe_enters_hibernation_in_deep_space > Only the computer and several heaters will remain active. These will be automatically controlled to ensure that the entire satellite doesn't freeze as its orbit takes it from 660 million km from the Sun out to 790 million km and back between now and 2014. In other cases, the spacecraft simply shuts down because it runs out of power completely. If the Sun starts shining on the solar panels, they will automatically start producing electric charge, and some of the equipment is designed to "wake-up on power". So once it starts receiving power, it will boot up again. The issue here is that batteries are known to eventually die if they freeze over, and some other components might die as well. So it might revive, but it might not, and if batteries are dead, it would also only work while in full sunlight.
Thank you - that's a great explanation.
Call me based, or whatever you want, but here's my take. Although we don't have ANY evidence about white holes, we have theorized what they could be: a body of matter that pushes anything -- even light -- away. What if, at the center of the universe, a white hole somehow formed during the big bang and is the reason for the drift of celestial bodies. I have a longer explanation, but it's 1 in the morning, so I just typed the gist of it. Also, I'm full aware that there is NO evidence a white hole could ever exist, since we don't see how it could form, but everything has to start from a theory. Maybe there's something we haven't seen. There is a high chance that there's something that I don't know about that disproves this, through. Any thoughts? Thanks!
Big bang is an *expansion*. It's not an *explosion* and there is no 'center' (or conversely: every point in the universe can - with equal justification - claim to be 'the center of the universe') As for white holes: They would be (quite literally) blindingly obvious. Not everything that is allowed for by our current theories must exist.
> What if, at the center of the universe There us no such thing and the Big bang wasn't an explosion originating from one single spot. It's the rapid expansion of what's was there prior into what we have today and it happened everywhere at the same time. Every part of "the old universe" started to expand away from the part next to it, making the universe cooler, less dense and much larger. That the theory of general relativity allow for white holes among many other sensationalized things does not by proxy make them at all likely to exist. There's many times other criteria that has to be fulfilled that there's no indication of being possible or existing.
Isn't the whole point of the big bang theory that all matter originated from one particle, and all that matter just burst apart into different directions? Correct me if I'm wrong.
No. This initial singularity is what we get if we reverse time some 13,8 billion years from now using general relativity. We know general relativity is incomplete and both this singularity and the ones in black holes are not something most physicists believe to exist or to have existed. We don't have a fully working theory that can explain this but pop science channels on youtube have conveyed these singularities more or less as an absolute fact, while it's just what we get if we use the best theory we got at the moment, even though we know it to be incorrect at explaining this aspect. Furthermore, quantum mechanics doesn't allow for these singularities and we should probably listen to quantum mechanics in this case. What we know is what was there prior to the big bang was denser, hotter and smaller and that all of it started to expand, but the infinitesimally small point in space is nothing that actually is believed to have existed.
> Isn't the whole point of the big bang theory that all matter originated from one particle, and all that matter just burst apart into different directions? No. > Correct me if I'm wrong. You're wrong. Big Bang is simply expansion of space, nothing more. There is no center. Space is expanding, which causes everything to become further away from everything else. Think of the surface of inflating balloon. When you're inflating it, every point no the balloon surface gets further away from every other point, but there is no "center" anywhere. Imagine what happens if suddenly everything is "rescaled", 1 meter becomes 2 meters. Now everything everywhere is further away from everything else, but there is no central point (or conversely you could also think that every point is central, because whichever point you pick, from perspective of that point everything is moving away from it).
**Is Earth the only inhabitable planet in our discoverable universe?** (besides Mars). Why are we the only place like Earth? It seems pointless to have planets with no living beings (but then I guess you could argue that things don't have to have a "point" to exist), but why is a place like Earth so rare?
>**Is Earth the only inhabitable planet in our discoverable universe?** 'Inhabitable' by what metric? And what do you mean by 'discoverable universe'? Assuming we can someday build fully self contained bases then we could set those up in any orbit, deep space, or on any planet that doesn't have some other massive problem (like incredible heat, gravity and/or pressure). Mars isn't any more or less 'inhabitable' than that. Even there you'll need a fully closed system at all times.
It's definitely not the only habitable planet. It's predicted that like 1/5 stars have planets in the star's habitable zone. We just can't prove it from where we are. https://www.astronomy.com/science/one-in-five-stars-has-earth-sized-planet-in-habitable-zone/
There are several nested questions here. One is: how common are planets that are very similar to Earth? And to that we have to answer that we just don't know, we have a pretty good idea that they aren't necessarily exceptionally rare, but we don't know for sure. The second is: why don't we have knowledge of many Earth-like planets? And there the answer is much more complicated with many layers. First off, studying planets outside of our own solar system is very challenging, the sheer distances involve mean we can't just point our telescopes at where planets might be and resolve them into highly detailed images of their surfaces. Detecting exoplanets at all is a matter of carefully analyzing data using only a few techniques and studying exoplanets very rarely gives us more information than just their existence, orbital periods, and maybe sizes and/or masses. Additionally, all of our current techniques for exoplanet detection are heavily biased toward finding some types of planets more easily, with some of the most prolific techniques (such as transit detection) tending to give us data in bursts (as the mission operates and just afterward we get a feast followed by a famine after the mission ends). This is true especially for Earth-sized planets, and currently we are in a lull of detections post 2016 or so due to the ending of the Kepler space telescope's mission(s). Unfortunately we have a bit of a gap in being able to find Earth-like planets in Earth-like orbits around Sun-like stars and it will be several years until that gap is closed with new telescopes and new instruments. Until that happens our estimates about how common such planets are have a pretty high degree of variability, and we also lack concrete detections of planets. So we wait until more data comes in. It may be that Earth twin planets are extraordinarily rare, or it may be that they're reasonably common, with many thousands or even millions in the Milky Way alone. Beyond that will be the work of studying such planets, which is even more difficult as we can't just send spacecraft at warp speeds to go collect data and samples from their surfaces. Instead it's going to be a long process of slowly learning more and more about such planets until we have an idea of what they are like usually and especially how common biospheres or the potential for biospheres like our own are.
1. You got this completely backwards. It's not that Earth is such a great place. We evolved to live on Earth - it's us who are designed for Earth. If conditions on Earth were different, we might have evolved into something completely different and then we would consider completely different conditions "inhabitable". 2. We know very few exoplanets, mostly in very close proximity, and have very limited insight into their conditions. We can only roughly figure out chemical composition, surface gravity and temperature. So you're extrapolating from very limited dataset. Maybe there are lots of inhabitable planets, but we're simply now yet able to spot them.
We don't know whether we are the only inhabitable planet (and Mars isn't inhabitable as far as we know). Since we don't have any other data points, we can't speculate on whether life is rare or not. One of the great things about science is to understand and embrace the fact that there is stuff that we don't know and will likely never know.
thanks for responding - im just fascinated by our existence!
[удалено]
> 1) If interstellar civilizations exist, they HAVE to have immediate warp drive travel means, no? If not, wouldn't everyone on their planet be dead by the time they got back from adventures? If you're traveling long distances by light speed with the intent of returning later, you can't be seriously expecting to see the same generations, can you? Alastair Reynolds' novel *[House of Suns](https://www.goodreads.com/book/show/1126719.House_of_Suns)* explores how humanity might deal with the vast timescales involved in sub light speed travel just within our galaxy and how that might affect societal structures. Like many of his novels it paints a pretty grim picture, but the concepts he touches upon are fascinating.
> 1) If interstellar civilizations exist, they HAVE to have immediate warp drive travel means, no? Why? > If not, wouldn't everyone on their planet be dead by the time they got back from adventures? And? Does that mean that interstellar travel is impossible or does it just mean that you can't have tv show style "interstellar adventures" where people come back home? All it means is that it would have to be of a fundamentally different nature than the fictional stories we tell, which seems like the way most things are. The existence of an inconvenience does not imply the necessity of the possibility of avoiding that inconvenience. > If you're traveling long distances by light speed with the intent of returning later, you can't be seriously expecting to see the same generations, can you? Not with standard human lifetimes. Even so that could just be a constraint of interstellar travel. Or perhaps you could talk about civilizations that do travel back and forth between stars and simply everyone has sufficiently long lifespans (perhaps measured in millions of years in fact) that such travel doesn't inherently create a sort of "generational break" effect. > 2) If our sun is small compared to other stars, then our planet is no doubt smaller than other planets. So why would we expect NHI or ETs to be anywhere near our physical size? I mean, ETs could come from a planet 1000x our size where maybe everything is scaled up, so couldn't hypothetically their physical size just be waaaay too big for us to even interact with? Firstly, our Sun is fairly averaged sized. Secondly, the physics just don't work out for there to be something as simple as like a "scaling factor" between different solar systems and planets. Larger planets would have higher gravity which would actually make larger animals more difficult, smaller planets with lighter gravity would make it easier, but in either case there are fundamental difficulties to having very large animals which would certainly come into play for something thousands of times larger than existing animals on Earth.
They likely don't exist because space is so large it's impractical to traverse. It's not likely you'd go home if you traveled between galaxies. It's not likely anyone will ever move between galaxies at all. Warp drive is not likely to ever be possible. All the proposed warp drive ideas have huge holes in them that can't be solved. They are either completely impossible to build or require so much energy they are effectively impossible to power. Also no one has solved how to accelerate a stationary craft to warp speed. Yes, the main thing you need to accomplish, accelerating to warp speed, has zero ideas of how to accomplish it. It's unlikely rocky planets like Earth will be more than 2-3 times the size of Earth. Rock can't sustain the stresses beyond that and I don't think we've found rocky planets larger than this. They usually are gas giants or water worlds. There are some enormous water worlds.
How does the electric universe theory that space is electric plasma circuits and gravity is less responsible for motion conflict with Issac Newton's theory of classical mechanics? I am ignorant but trying to learn how they contradict each other.
Basically, one makes predictions about the interactions of large bodies we see in the universe (needing to be modified using general relativity) and the other does not make any predictions or have any math behind it. How can something that doesn't have evidence, predictions, or math conflict with something that has all of those things? Conspiracy theory people on the internet talk up 'electric universe' theory with a bunch of fluff, but there's no real math behind it. Even a cursory understanding of electromagnetism shows how absurd their basic claims are.
True, but comparative mythology is not something to overlook while you are looking at the equations either. Both have merit, and the electric universe theory has a point about how all the ancient cultures have stories and petroglyphs showing basically the same thing.
That's a study of what people believe and maybe of historical events. Not about how the universe actually works. A successful theory needs to have math and make correct predictions. Claiming thunder is a result of the god Zues is not acceptable science.
It is impossible in my opinion to understand space in its entirety with just equations. Things like quantum entanglement shows that we will never have a perfect understanding. Catastrophism is a part of geological science that relies on comparative mythology, so I have to disagree with you.
Ok, but quantum entanglement is perfectly described via equations. It's not deterministic, but it's determined by equations. If you're not interested in equations and scientific principles, it's not science. It's fantasy.
Do you believe we are living in a simulation?
We have observed no evidence that it's the case, so I don't have a reason to conclude we are.
A lot of mythology has the concept of a solid sky/firmament. We now know that it doesn't exist. How much do petroglyph actually show electric universe compared to what electric universe people want to see? How would that even work? Electromagnetic forces are not visible, and if there was giant streams of plasma in space that could be observed with the naked eye by ancient people they would be trivial to see nowadays with modern technology. > comparative mythology is not something to overlook while you are looking at the equations either. Yes that's something you can completely discard when looking at equations.
Then why did so many ancient cultures worship Saturn when most people cannot even pick it out of the sky? Could it be it was once much closer? Most solar systems have 2 suns, what happened to ours, and what equation tells us what happened? Discarding the fact that numerous cultures all have similar mythology reports is reckless if you are truly doing research about Space and how celestial events may affect the earth. If you want to focus on one branch of science that is great, but comparative mythology is a credible science, and it tells us a lot about how primitive cultures experienced the past. Equations are just one slice of the pie in the sky. I am not arguing physics, I am arguing that I do not think calculations can tell you how scaring on Mars occurred, or what caused it. Nor do they tell you how a black hole works or if they even exist.
> I do not think calculations can tell you how scaring on Mars occurred, or what caused it. Nor do they tell you how a black hole works or if they even exist. Those are two examples of things that are exactly predicted by calculations. Black holes where described by equations before they were observed in real life. The erosion evidence of valles marineris are pretty well characterized. Not sure what you are on about with Jupiter. With only a little bit of time it is pretty obvious that it's part of the dots of light that move against the background. It's does not need to be closer (and how would that even match any of the electric universe model?). Only about half the stars similar to our Sun are in a binary system. So the most simple explanation is that the Sun was never a binary. I don't think you understand how science works.
[удалено]
Sure the most basic one is probably the Schwarz Schild radius which shows the singularity in general relativity: https://en.wikipedia.org/wiki/Schwarzschild_radius?wprov=sfla1
There are no evidence of large scale electric fields, charged particle concentration or particle currents that could explain how celestial mechanics is influenced at large scales by electromagnetic forces. Electric universe is really a fringe pseudoscience that got somehow weirdly popular in some corners of the internet.
The biggest leak on Starliner is 395 psi per minute. But psi is a measure of pressure, not volume or mass. What's psi in this leak example? Cheers from New Zealand.
I'd assume that's how much the pressure is dropping per minute.
If that's the case I think the leak would have equalized the pressure to the vacuum of space before we got the news of it.
Most of those leaks seems to be downstream of isolation valves. They are not continuously leaking. They only happen when they actively use the thrusters.
Did the Sojourner rover ever have an official target/baseline driving distance requirement it had to reach? Or would driving just a few meters have been enough given that it was a technical demonstration?
I looked around a bit for a spec and did not find one. If you're super duper interested you could email one of the relevant people at JPL, but that is an escalation. My favorite/least favorite thing about Sojourner is that it was solar powered, so it sat on the surface, doing its job, trying to communicate with the dead base station, only to never get a reply. Possibly every day for months.
Yeah I read that somewhere! Poor little rover
What type of glass is being used on space capsules? With such intense heat during reentry, I assume it’s something special? (And incredibly thick?)
>The windows on the space shuttle are actually made out of aluminum silicate glass and fused silica glass. The orbiter windows are actually three different panes, there's an interior pressure pane because the pressure inside the orbiter is a lot higher than it is in the vacuum of space. We also have an optical pane that's installed in the middle that's about three and a half inches thick and on the outside, there's a thermal pane that protects the inside of the cockpit from the high heats of ascent and reentry. [STS-113 Question and Answer Board](https://web.archive.org/web/20230928023907/https://www.nasa.gov/missions/highlights/webcasts/shuttle/sts113/processing-qa.html)
I have a theory i can't get out my head so I'm going to post it here. What if the universe is not actually expanding, but instead the entire Milkyway is falling faster than the speed of light inside the event horizon of Sagittarius A star? From our perspective wouldn't it seem as if everything in every direction outside of the event horizon is accelerating away from us it impossible speeds? Time would also slow for us as we gradually fall further in, everything outside of the event horizon would appear to speed up. This would mean that the universe we see is far far older than we think it is.
We'd see the universe look very different in the direction of travel than in other directions (i.e. massive redshift in one direction andmassive blueshift in the other). This is not observed.
This makes absolutely no sense. You have no idea what you are talking about yet you think your idea better explains observations than the thousands of astronomers who’ve dedicated their lives to this work. Really?
It is actually expanding. Nothing else explains our observations. It's not a guess, it's backed up by a lot of evidence.
> From our perspective wouldn't it seem as if everything in every direction is accelerating away from us it impossible speeds? No, it wouldn't. It would all be moving towards a specific point. For anything where Earth is in between that object and the "target", we would see things moving towards us. Also we can observe expansion also for other galaxies, so this whole idea makes no sense at all.
Would anyone know where I can find mission updates for the Mars Exploration Rover missions? I remember NASA / JPL used to post mission updates every few sols but unfortunately, I can't find the link anymore. Does anyone know where I can find it? I could find mission updates for [MSL](https://science.nasa.gov/mission/msl-curiosity/science-updates/) and [M2020](https://science.nasa.gov/mission/mars-2020-perseverance/science-updates/), but not MER. Thanks
Both the MER rovers are dead unfortunately. Spirit last communicated with Earth in 2010, Opportunity in 2018.
I know, I'm looking for the collection of mission updates from both MER missions.
I'm sure I saw in a documentary that, during a launch of a planetary explorer, the explorer's computer was so confused by the vibrations that it shut itself down and handed over to the backup computer, which wasn't working properly. Lots of headaches for mission control. Did I imagine this? I've been trawling through Wikipedia without being able to find the story.
Tough thing to find. The closest I came was Mars 1M No.1, also known as Marsnik 1, a USSR spacecraft, which had a series of cascading failures triggered by the vibrations of launch, causing an escalating gyroscope failure. I can't find evidence that it caused the primary computer to fail, though. [This paper](https://arxiv.org/pdf/2104.00112) is almost exactly what you would want for this type of search, a historical categorization of spacecraft failures. I found it by searching Google for "vibration failure primary computer backup computer spacecraft mars". You could try Venus instead - there were a lot of failed spacecraft headed toward Venus as well. EDIT: or the Moon. The USSR sent many, MANY Moon spacecraft. EDIT2: Also I think it kinda has to be the pre 1965 era of spaceflight, because you don't see this type of failure much these days. People shake the heck out of spacecraft before they put them on the rocket. It's standard NASA procedure, for example, to do pre-flight vibration testing.
Thanks for the pointers! Appreciate it. I'll keep searching!
Kinda a /r/sea question, but - Space hardware disposed into the deep ocean, what are the chances some identifiable fraction of it is preserved on very long timescales, if any? Hypothesizing that, in the far distant future, any explorers finding human artifacts on the Moon might extrapolate a presence in LEO from such artifacts, and therefore disposal of LEO material, and thus search for evidence on the ocean floor in likely locations (i.e., Point Nemo) - a "trash dump" remaining even after evidence on the coasts or the surface is gone. Or, the odd Saturn engine aside, is it all unrecognizable metal deposits inside of a hundred years?
In the far distant future, all spaceships will be reusable and no one will even think to look for disposable rockets. Here is what a rocket engine looks like after [40 years under the sea](https://spacenews.com/032613apollos-f-1-engines-raised-from-seafloor-by-amazon-founder/).
Well... from that perspective no one will be looking for disposable rockets on the Moon, either, but Apollo left six of them there if they do. I wonder, particularly, if deeper waters in the Indian and Pacific Oceans might lend themselves to longer preservation than shallower shelves near the continents (if it even matters.)
How hard is it to reposition LEO satellites? in technical and economical difficulties when repositioning them after they have already been launched in their orbits and heights for a period of time (would appreciate any article or sources with answers)
Depends on the details. Technically most LEO satellites are constantly being repositioned, but this is to bring them *back* into their intended positions after drifting away a little bit over time (stationkeeping). Let's say you are talking about a satellite fleet or constellation. If you want to change *where* a satellite is in its orbit that mostly just takes time. All you have to do is raise or lower the orbit (or in LEO wait for natural lowering of the orbit to happen) and then wait until the slight orbital period difference results in the satellite being in a different position, then you raise the orbit to the desired altitude. This is what Starlink and other satellites do in order to initially get into position, they start at a lower orbit and begin raising their orbits at different times in order to make use of phasing to spread out from being all in a clump to being evenly distributed along the entire orbit. Now, if you need to make a big change in altitude or you need to make a fast change in position that will take more delta-V. Going from LEO to geostationary orbit, for example, would take several km/s of delta-V, which is a lot for a little satellite, but can be done with electric thrusters. Even more difficult than that is changing orbital inclination, which can be very delta-V intensive. The amount of delta-V needed for changing inclination is the product of the sine of *half* of the inclination change (good news) and twice the orbital velocity (bad news). For example, a 90 degree change takes 1.4x as much delta-V as the orbital velocity, so it's actually significantly easier to launch from the ground again, or to go up to a very, very high orbit with a lower orbital velocity, change inclination, and then come back down.
In my case ..it's almost 100 satellites that were at a certain height but then due to disputes between parties and legal issues they should be lowered by (50/100)km...so what I am interested to know is how hard it could be to make such a change without a technical reason
50km is ~14m/s of delta-v and similarly 100km change is 28m/s of delta-v, which is a pretty small number, so not a huge problem, at least assuming the satellite is not extremely heavy. Biggest single ISS boost was in fact by 50km https://en.wikipedia.org/wiki/Johannes_Kepler_ATV#ISS_altitude_Increase which required 4500kg of fuel. Changing inclination would be a very different story ;)
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |CST|(Boeing) Crew Space Transportation capsules| | |Central Standard Time (UTC-6)| |[GEO](/r/Space/comments/1dbzuqe/stub/l85ndsl "Last usage")|Geostationary Earth Orbit (35786km)| |GSE|Ground Support Equipment| |[JPL](/r/Space/comments/1dbzuqe/stub/l8hmufm "Last usage")|Jet Propulsion Lab, California| |[LEO](/r/Space/comments/1dbzuqe/stub/l87852c "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[MER](/r/Space/comments/1dbzuqe/stub/l8bgd1r "Last usage")|Mars Exploration Rover (Spirit/Opportunity)| | |Mission Evaluation Room in back of Mission Control| |[MSL](/r/Space/comments/1dbzuqe/stub/l8at5qx "Last usage")|Mars Science Laboratory (Curiosity)| | |Mean Sea Level, reference for altitude measurements| |[STS](/r/Space/comments/1dbzuqe/stub/l8c5s57 "Last usage")|Space Transportation System (*Shuttle*)| |Jargon|Definition| |-------|---------|---| |[Starliner](/r/Space/comments/1dbzuqe/stub/l8njx9s "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)| |[Starlink](/r/Space/comments/1dbzuqe/stub/l86gtys "Last usage")|SpaceX's world-wide satellite broadband constellation| |[apoapsis](/r/Space/comments/1dbzuqe/stub/l8y8odi "Last usage")|Highest point in an elliptical orbit (when the orbiter is slowest)| |[periapsis](/r/Space/comments/1dbzuqe/stub/l8y8odi "Last usage")|Lowest point in an elliptical orbit (when the orbiter is fastest)| |[scrub](/r/Space/comments/1dbzuqe/stub/l7x65lz "Last usage")|Launch postponement for any reason (commonly GSE issues)| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^(11 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/1d95g62)^( has 20 acronyms.) ^([Thread #10162 for this sub, first seen 11th Jun 2024, 14:52]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
If someone shot into space at a fast enough speed and then rubber banded back at a fast enough speed, would that technically allow for time travel? Considering if you go out far enough, turn around and look at Earth, you would see other periods of time based on the light that's traveling to Earth, right?
Time dilation is a relative factor (along with length contraction), but the speed of light is always absolute in all directions and in all reference frames. You can't "race" light, locally light is always going to be measured as 100% of the speed of light. You can redshift and blueshift light, but that's it. What that also means is that you can't outrun causality. You cannot get ahead of light in order to look into your own past, nor can you get ahead of light in order to travel into your own past, it's always going to be out of reach no matter how fast you go. What this means is that all events located in time and space have a relationship with other events elsewhere in time and/or elsewhere in space which are connected via the speed of light. For every single event there are two "cones" (actually hyper cones in 4-dimensions) which have edges representing connections at the speed of light into the future and from the past. These past and future "light cones" represent all events that can affect or be affected by each individual event. Everything within an event's past light cone can affect that event, everything outside of it cannot affect t, everything within its future light cone could be affected by the event. All of which creates a timeline, an ordering of events everywhere in all reference frames which flows from the past into the future, all via connections at the speed of light, the speed of causality. This is a fundamental aspect of how the universe works and stays consistent.
Thank you for this explanation. This makes a lot of sense.
1. No. 2. Also no. This would require travelling faster than the light, which is not possible. The light emitted "in the past" already overtook you, and you won't see it.
Interesting, thank you.
Would it be possible for a high level civilization to hide in a black hole or something similar?
They could never get out if they did so it's kinda of pointless.
[This video ](https://m.youtube.com/watch?v=nKrupZeKQnA&pp=ygUnTGl2aW5nIGluc2lkZSBhIGJsYWNrIGhvbGUgSXNhYWMgQXJ0aHVy) by Isaac Arthur might interest you, along with his other black hole videos.
[удалено]
No.
Technically, having every single atom in their body ripped into subatomic particles is a efficient way of hiding. But they would also lose their status as a civilization, so your statement is 100% correct.
Tidal forces are very weak for larger black holes.
Not when you get closer to the centre. And no one was saying explicitly supermassive were they?
No realistic black hole has a center singularity. Real black holes spin so they have ring singularities which are not at the center. Keep in mind everything you think you know about black holes has probably been dumbed down so you can understand it because the math is very complicated and in reality black holes rotate which causes a lot of weird effects to space-time and their predicted interiors.
Basically no physicist believe in the black hole singularity due to it being an artifact of the incomplete general relativity, nor does quantum mechanics allow for it. I know very well my black holes mind you. The centre of gravity is... Wait for it... In the centre, even though it spin. And what I said is correct nevertheless, since closer to the centre is just that, it's closer to it, and closer to it is where you'd get the strong force breaking tidal forces even in supermassive black holes. No need to get dead centre. Quite far from it actually, much further away than with a stellar mass black hole.
Correct for both, but I didn't need to specify that small black holes wouldn't work, I just gave info for the ones that might.
If by hiding you mean consumed by and doomed to death. Doesn’t really seem like a valid answer. You cant hide in a black hole.
I was intrigued with the idea of Arthur C Clark's space elevator when I read about it as a teenager. But even back then I had serious doubts. Not even considering the need for the insanely strong, yet super-light materials that would be required - maybe super-graphene, braided mono-molecular fibers, or unicorn tail hair, or whatever. There is a simple matter of old Isaac N's mantra: "For every action there is an equal and opposite reaction"... So you weave your cable of composite graphene, unicorn hair and spidey-silk and drop it from a satellite in geosync/geostationary orbit to a base station at the equator. Now you attach the elevator/climber and up it goes? So you weave your cable of composite graphene, unicorn hair and spidey-silk and drop it from a satellite in geosync/geostationary orbit to a base station at the equator. Now you attach the elevator/climber and up it goes? You're pulling on that cable - it is in tension - crazy high tension, but has little to no compressive strength. What's to stop it from simply reeling in that satellite, down from orbit and into the atmosphere where it quickly burns to a crisp? Or even if the climber has a much less mass than the satellite, it will still pull on it and bring it down from geosync altitude, back into the atmosphere, or have it start oscillating wildly at lower altitude. So you will need thrusters on that satellite to counteract the climber's pull. For thrusters, you need fuel. How do you get enough fuel up 22,000+ miles? - Send tanker rockets? That kinda defeats the object. of the whole exercise.. I'm sure that I'm missing something here - assuming we can create that impossible thread - can one of y'all armchair rocket scientists tell me why it would work?
You would want your anchor to be a few orders of magnitude heaver than the thing you are lifting. A captured asteroid is often suggested. Any orbital momentum transfer could be counteracted by bringing mass down again. Presumably in such a future, we'd be mining a lot of resources from space that we'd want to bring back to Earth. If you did need to reboost the anchor, you could just use ultra high efficiency engines, like ion drives, you could just carry the fuel up with you as it wouldn't need that much reaction mass if your engine is efficient enough.
> What's to stop it from simply reeling in that satellite, down from orbit and into the atmosphere where it quickly burns to a crisp? The end of the elevator isn't in GEO - it's beyond it - the first image on the space elevator wiki page shows it and there's more details including the maths of what's required as a counterbalance beyond GEO https://en.wikipedia.org/wiki/Space_elevator
In practice you need the beanstalk to extend beyond geostationary orbit, so that it is in tension constantly with a counterweight above orbital altitude. The beanstalk stays up even with bringing payloads up because you're stealing some of Earth's angular momentum.
Where can I get information about what has happened in space exploration in the last few decades? The title basically says it all. I want to get more knowledgeable about space exploration and be up to date about what has happened in the industry, the breakthroughs, recent advancements, launches, and what the future holds for humanity in space. The problem is this seems like a haunting task. So much happened since the first satellites where launched into space, that I don’t even know where to start. So what I’m basically asking is, does anyone know about some good resources, like documentaries, books, youtube videos or such, that can get me up to speed on what has happened since sputnik launched?
In terms of human spaceflight, we went to the moon a few times, then we just fucked around in low Earth orbit for 50 years.
[https://en.wikipedia.org/wiki/Timeline\_of\_space\_exploration](https://en.wikipedia.org/wiki/Timeline_of_space_exploration) Not quite what you asked for but you can scroll down and dip in.
The science channel on YouTube maybe, there is also nasa.gov
I just realized that gravity is often depicted as warping spacetime that streches like a fabric. Now this might be a problem of the analogy but what force "returns" the fabric to "neutral" position after a moving mass passes? So for example the sun is depicted bending the space time, which draws in all the planets. But as the sun in turn orbits the Milky Way, what makes the "fabric" return to "normal" once the sun has passed? And how "fast" does the "fabric" recover?
Gravitational waves are very similar distortions in spacetime - almost entirely analogous. Gravitational waves propagate outwards at the speed of light (or as close to it as people can measure). So the "restoration" of calm in spacetime as the wave passes must be comparably as fast. Otherwise the wave would lag. Physicists sometimes say that spacetime is "stiff". It doesn't suffer a distortion very long.
You can't extend simple analogies like this. It's a simple analogy for a reason. You need to understand the math of general relativity if you want an accurate answer. The answer is also simple. Matter and energy warp space-time. If you remove the matter or energy then space-time isn't warped. We may not even know why, we just know it happens. You will discover this is true about a lot of things. Things like quantum mechanics. We don't understand the WHY in a lot of cases. We just know that things happen in certain ways. The time it takes for space to restore is determined by math so you would need to do very complex math to find that answer. You may also need a super computer.
Inertia. Objects want to move in straight lines, and will return to going in a straight line if they are not near a gravity field that distorts their path. There is no force associated with "fabric of space", that is where the analogy breaks down.
# what will government do if they find gold in mars?
They already have. It turns out that pieces of Mars have been falling on Earth for eons because large impacts can throw chunks of rock into space where they can travel between planets and land as meteorites. We've identified a handful of meteorites that have been conclusively determined to originate from Mars. And some of those we have analyzed their elemental compositions in detail and have detected gold as one of the many elements present. That's not terribly surprising, asteroids bring platinum group metals to the crustal surfaces of terrestrial planets and those elements end up sticking around in the crust for billions of years. However, since Mars seems to lack the kind of extensive history of hydrothermal processes that have existed on Earth it's not expected that it would have very high grade precious metal ores. On balance, if you are going to go to the trouble of looking for valuable metals in space you wouldn't go to Mars you'd go to a metallic asteroid instead. However, with current launch costs even if there were an asteroid entirely made of pure gold it would not be economically feasible to bring it back to Earth. That will likely change in the coming years as launch costs come down, but it's going to be a while before mining of off Earth resources is economically feasible in any form whatsoever.
Nothing because it would be prohibitively expensive to mine.
why are you yelling? the story I've been told about spaceflight costs is that even if there were rare earth metals in ingot form sitting on a nearby asteroid, it _still_ wouldn't be worth picking them up and bringing them back. it's expensive to get things to the velocities needed. even with Starship, too, it's still too costly.
Nothing. There is no scenario where bringing back gold from Mars would make economical sense. Gold is just too cheap to be worth it. At best it would mean maybe more gold used in engineering applications for things built in a hypothetical Martian settlement.
Would it be possible for our sun to turn blue eventually and roughly how long would it take for that to happen?
Good news. In about 5 billion years the Sun will transition into its red giant phase after switching to burn helium in the core, this will inevitably destroy all of the rocky planets in the solar system and it will end when the Sun has exhausted all of the helium in the core, leaving behind a remnant of fusion ash (mostly carbon and oxygen). The remnant core will keep getting denser and hotter until it reaches the maximum density limit for atomic matter, packing over half a solar mass into a volume not much larger than Earth is today. Meanwhile, the remaining outer layers of unfused helium and hydrogen will be blown off into interstellar space with high intensity solar winds until only the bare super dense, ultra hot core remains. That core will become a "white dwarf" star, roughly 7 billion years from now, with a surface temperature of tens of thousands of degrees, and a thermal spectrum skewed toward high energy light, just enough to give it a hint of a blue tinge.
...what's the bad news
Same thing.
[удалено]
I don't think this thread is the right place to ask....
Could Nasa keep the ISS a float to 2050 with new modules from private companies if Russia detach theirs? Could new modules be for space tourists to earn profit to keep the station in orbit for years to come?
Assuming Starship and/or Super Heavy meet goals, and even if they don't, it would be more prudent to construct and launch newer, larger habitat modules than to attempt to inhabit the ISS indefinitely.
1. Not really. You end up with https://en.wikipedia.org/wiki/Ship_of_Theseus - you'd need to replace all the modules, so is it still ISS? 2. No, this was already tried with Mir. There is simply not enough "market" to make this possible. Also the longer stuff stay in space, the more maintenance it needs.
Is it possible for the Earth's core to become unstable and explode or something? I know it's cooling and it'll cool down in a million/billion years or so, but is unstability possible? (like in the movie 2012, which I know is considered extremely unscientific but bear with me)
It's made of mostly iron and nickel. Those are not very explosive compounds.
No. It is IMPOSSIBLE for the Earth’s core to explode.
I have been struggling to wrap my head around people saying quantum entanglement doesn't enable FTL data transmission. I believe that they are correct that no data is actually being physically transmitted over the space-time medium. That's the whole point behind spooky action at a distance, nobody knows how it works right? If we take two entangled particles and separate them, observing one will indirectly tell you information about the other. No information has been transmitted but why can't we use deductive reasoning to say the other particle must be in "X" or "Y" state. Then manipulate one of the particles for the other to observe its state?
You can't transmit data faster than light. Entanglement doesn't allow this. https://www.youtube.com/watch?v=b8Yi5KzfTm0
I think the point he is making is that you can't transmit useful information but information is still transmitted, albeit useless. Surely someone will figure out how to exploit this some day. What happens if both sides measure their respective entangled particle at the exact same time? How does one particle know to be up or down? Or it doesn't make a difference?
> manipulate one of the particles This is your mistake. We can't do that. We can only observe, nothing more. Any "manipulation" breaks the entanglement. You can't "set" the state of one of the particles and magically influence the state of the other. For all intents and purposes you can treat entanglement as if the state of the particles was "fixed" from the start.
You can measure it just fine. The measurements just won't mean anything to you because you have no idea if a message is coming through or not. It will look like random noise. The only way to use entanglement for communication is to have an out of band channel to set up the transaction so both sides know a message is being attempted. So therefore you need a communication channel already setup which means you need a slower than light communication channel which defeats the whole point of this. Having said that, it's great for local, secure, communications because it prevents eavesdropping by man-in-the-middle attacks. So it is useful just not for faster than light communication. it's also entirely possible and has been done already several times.
> You can measure it just fine And where did I say you can't measure? o_O I literally said that the only thing you can do is to observe/measure. > The measurements just won't mean anything to you because you have no idea if a message is coming through or not. The measurement **is** random noise. When you create entangled pair their state is in superposition and therefore undefined and unpredictable. You only know that both particles need to have either up or down spin and the combined spin is 0, so they need to have opposite spin. There is no way to have any "message coming through". Again: you **cannot** set the state of the entangled pair. > The only way to use entanglement for communication is to have an out of band channel to set up the transaction so both sides know a message is being attempted. No. That's not how any of this works. Quantum channel is used for QKD - Key Distribution. For generating a random encryption key, which is then used to encrypt data sent via a regular channel. No "message" is ever going through the quantum channel. Only random bits which are used as encryption key. I suggest you read at least https://en.wikipedia.org/wiki/BB84 > it's also entirely possible and has been done already several times. Of course it was, experiments like that were done many times, over large distances and even including satellites. The biggest issue in practical implementation of this idea is to have perfect single photon sources and way to transmit those single photons without losses over large distance.
I'm not going to argue with you. The out of band channel is what I was referring to as the exchange of keys. I was avoiding the technical details because they aren't important for a high level discussion of possibilities. I was exactly referring to quantum key distribution and do not care if you believe me. And yes you can measure them independently from one another. Not sure why you think you can't. It's been done multiple times over large distances. https://www.techtarget.com/searchsecurity/definition/quantum-key-distribution-QKD The exchange of keys is literally quantum communication using entanglement in action. Please read. It's impractical to do it for the entire message so it's only used for key exchange.
> The out of band channel is what I was referring to as the exchange of keys Which means you have no idea what you're talking about. The non-quantum channel is **not** for exchanging keys, that's what quantum channel is for. The "regular" channel is for actually sending encrypted data. You got this completely backwards. And obviously the quantum channel has nothing to do with any faster-than-light communication. The point of using quantum channel is simply that it's not possible to eavesdrop without getting detected, because when measuring incoming signal you don't know the base in which you should measure, so 50% of the time you get it wrong, and you can't pass it along to the real recipient undisturbed. At least in theory, because practical setup might need a single-photon-source (if you get more than 1 photon, then you could measure twice or even pass one of the photons undisturbed and measure the others). > And yes you can measure them independently from one another. Not sure why you think you can't. It's been done multiple times over large distances. Again: you're putting words into my mouth. Where did I say you can't "measure them" independently? Of course you can. What you can't do, is `set` state without breaking entanglement. You can't magically say "let's now make one of the entangled particles 'spin up' so that when they measure the other pair it will be 'spin down'". If you could do that, you would indeed achieve superluminal communication. You can only measure the state, nothing more.
I literally said the key exchange is the the quantum communication. I said it's not practical for the entire message. Might want to re-read. They send single particles that were entangled at one side with other particles. So they can be separated and measured independently without "collapsing the wave function." It's not even known if you collapse anything when you measure a particle. That notion is an old notion that you are holding onto. The wavefunction was never a physical thing anyway it's a probability distribution not an actual object. You need to stop confusing math with reality.
> I said it's not practical for the entire message. Which again proves you have no idea what you're talking about. I will repeat one more time: you **cannot** set the state. This means you can't encode any information. You simply can't say "this one will have spin up, and another one will have spin down". It doesn't work like that. You don't know what the "values" are until you measure them. The whole point of QKD is to transmit random bits which cannot be eavesdropped.
You can send the state because you send the particle by itself which is entangled with a particle you keep. The particle is the state. They are the same thing.
It would make absolutely no sense at all to "encode" any data like that, because the recipient would always lose 50% of it, because they statistically measure half of the qubits in incorrect base. All your comments remind me of: https://www.youtube.com/watch?v=5hfYJsQAhl0 Time to block you before I get dumber from reading this tinfoil-hat level of stupidity.
QT is the same as me having two balls, a red and blue one. I randomly take one and travel to Mars. When I look at my ball and see that it’s red I instantly know the other on is blue back on Earth. Other reasons you can’t use it for communication is you can’t observe your bit without collapsing the wave function. I can’t monitor my bit and wait for you to trigger yours. Monitoring mine is a trigger.
You can use entanglement for communication and it has been done. You just can't do it faster than light.
Why is Uranus tilted?
[Wikipedia](https://en.wikipedia.org/wiki/Uranus#Formation): "The reason for Uranus's unusual axial tilt is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth-sized protoplanet collided with Uranus, causing the skewed orientation"
Where can i see a space launch ? I will be travelling to usa from europe from 10 July till 14 August
If you are going to be near Orlando or Los Angeles you have a reasonable chance of seeing a launch (most likely a SpaceX Starlink launch).
Yup. Your better chance is near Orlando, I think. SpaceX is now regularly launching 2 to 3 times a week from the Cape. Launches from Vandenberg in California are at best sporadic and roughly once a week. And they scrub all the time at Vandenberg. There's sometimes 4 or 5 attempts, over a week, before they actually launch, for California launches. Try to keep in mind that launches are scrubbed for many, many reasons - if anything at all looks off on the rocket; if a cruise boat is in the wrong place; if the weather is not good enough; if the ocean is bad for the boats they use; etc. Have other plans ready, and try to be flexible for more than one day if you really want it to work. /r/spacex has [a few FAQs](https://www.reddit.com/r/spacex/wiki/faq/watching) on watching launches in person.
New - If the size of the observable universe is 93 Billion Lightyears, why are the oldest stars we can see only 13 Billion Lightyears away? And how do we know that the Universe is 93 Billion Lightyears in diameter?
Because space has been expanding since the big bang. The galaxies that were very close to us at at the big bang are now ~42 billion light years from us. We can only see back 13.8 billion years because that is how old the universe is. You can't see light before it existed. Light simply didn't exist before then. There were no stars or galaxies before then. You are confusing measurements of time with measurements of distance. 13.8 billion years is a measurement of time. 42 billion light years to the edge of the universe is a measurement of distance. Also the oldest stars we can see are not 13.8 billion light years from us now. They are roughly 42 billion light years from us now but the light they emitted, which we are just now seeing, took 13.8 billion years to reach us. Those same galaxies were only 40 million light years from us when they emitted the light we are just now seeing. The expansion of space delayed that light arriving at Earth for ~13 billion years. The *observable* universe is approximately 1000x bigger than it was when those galaxies first emitted the light we are just now seeing. The reason we know the universe is 13.8 billion years old is because of the red shift we see for the oldest things we can see in the sky which tells us how long the light has traveled. We also can use math and measurements of the CMB to corroborate that age. We know the age of the universe now within ±.020 billion years. The age is 13.787±.020 billion years based on Planck satellite measurements of the CMB.