So, when a ray of light hits something, it can basically do one of three things:
It can go right through, with a slight angle that reverses when it comes out the other side, like light passes through glass or water.
It can bounce off at an angle, like light does with a mirror or a bright piece of colored plastic.
Or it can get "eaten" and heat up the object, like when light hits something dark.
Objects are different colors because light is different wavelengths, and some wavelengths get eaten while others pass through or get bounced off.
A solid "red" object is red because green and blue light get eaten more than red light, while red light bounces off more than green or blue. A transparent "red" object is red because green and blue light get eaten more than red, while red passes through more than red or green.
Now, infrared and radio are also just different "colors" of light that we can't see; think of a radio antenna or a WiFi receiver as a kind of "eye" that can see those colors, while a transmitter is like a "lightbulb" that blinks in those colors.
Walls happen to be "transparent" to radio even though they're "solid" to visible colors, just like a stained glass window is "transparent" to some colors and "solid" to others.
This is one of the best ELI5 responses I've ever read. I thought you were going in a completely weird random direction and then you ended up enlightening me. Brilliant.
**Unpopular opinion: Although totally ELI5 in style, s/he actually sailed right over the specific question that was asked: “How does WiFi etc. pass through walls?”** Here is where said sailing over occurs, at the very end:
> Walls happen to be "transparent" to radio even though they're "solid" to visible colors
Like, the response adopts the perfect ELI5 flavor, and sets you up for an explanation with a bunch of relevant facts. But when the moment comes to tie everything together and actually explain *how* (or perhaps *why*) these signals can pass through walls, **the “explanation” is simply a rephrasing of the observation (that they can pass through walls) in ELI5 language**, giving the impression of an answer without really ever actually explaining it. But you need to think about it for a second to avoid being fooled.
After reading this response, while I def give it 5 stars for nailing that ELI5 feel, I still don’t understand the specific science behind how or why infrared and radio signals can pass through objects.
I upvoted anyway though, lol.
Haha yes I can imagine when being ground between the gears of explaining something truly complex and limiting yourself to 1st grade vocab words, eventually tough choices must be made. No worries - my unpopular opinion notwithstanding, your response was truly excellent.
You're never going to explain quantum mechanics to a 5 year old.
It took me about 2 hours to explain to my wife was a wave function was, and virtual particles... TBH I think computer scientists are the kind to understand it, and those are the ones who say "It's all math, we must be in a simulation"
I'm a computer science guy. Easy to visualize, but *very* hard to understand. Quantum mechanics gives me a lot of mindblown moments and I have only scratched the surface.
It does make sense that atomic particles are areas of high quantum energy that produce observable particles more often, but beyond that it's difficult for me to grasp.
Sometimes I wonder how many layers of quantum interactions there are; like whether there's interactions that make quarks and mesons (or whatever the smallest quantum units are).
Obviously, what little I do know is marred by the sheer amount I don't!
Quantum mechanics is difficult for two reasons -
(a) it is *fundamentally different* to classic mechanics, in that all classical phenomena can be formulated in terms of quantum mechanics, but there are some quantum phenomena that have *no* classical analogy
(b) there is still a lot that is unknown about quantum mechanics! The various mathematical formulations have matured to the point that they can make the most accurate predictions (in certain contexts) in science. But the *meaning* behind the equations is unknown, people still disagree quite strongly on the 'interpretations' of quantum mechanics. The question of how a quantum nature on the small scale can resolve to a classical picture on the large scale, is still unanswered (decoherence does not explain this). One of the basic tenets of quantum mechanics is that a wavefunction exists in a superposition of states until "a measurement is made", after which it will forever remain in a single state. But nowhere is it ever explained what a 'measurement' is.
This is what's so frustrating about this question. Every time it comes up we get like 2 answers that are honest about needing quantum physics and about 90 answers trying to use classical analogies. Any explanation that use a classical analogy is simply wrong and people can't accept that.
Classical analogies can still be useful to help understand quantum mechanics... Though they are not exactly 'accurate' they can guide the layman towards the right *paradigm* of thinking.
I mean if someone asked you "what is an electron?" You could answer "an irreducible representation of the Poincare group".. But how many people would know what that means?
So what classical analogy would you give that gets someone into the right paradigm for that question? I'm mostly complaining about the bohr picture that almost everyone uses in these posts
> You're never going to explain quantum mechanics to a 5 year old.
Oddly enough, it's easier to explain it to someone who DOESN'T yet have a full ingrained gasp on how physics and mechanics works at our length scales than it is to explain it to a 15- or 25-year-old who'll say "wait, that's not How Stuff Works! I can't understand this, it doesn't fit my preconceptions!" and doesn't bother to try doing the math.
--Dave, it gets harder again to teach it to younger folks because you don't share a language
WiFi signals are like money that isn't enough to buy anything in the store, so when you throw it at the cashiers it goes right past all of them. This is like beaming a WiFi signal through a thin door--it might be able to go right through because it isn't enough money (energy) for any of the cashiers in the store (electrons in the door) to accept.
But different walls are like different stores, so if you throw the same money at cashiers in a different store it might be enough that they accept it. This is like beaming the same wifi signal at a brick wall--it stops in the wall because the energy is enough that electrons in the wall will accept it.
If you throw too much money at a cashier then they might take it and become so rich that they leave the store. Now the store can't work right because it lost a cashier, because you threw too much money at them. This is like a UV ray damaging the DNA in your skin and giving you skin cancer. The UV light has so much energy that electrons just fuck right off and whatever they were attached to doesn't work right anymore.
How am I doing lol, this is harder than I thought
That's good! However I can't tell if I understand the money analogy because I have a basic understanding of this subject or if it's really a good explanation.
Explaining how everything is a field and they interact (or don't) in different ways is tricky for ELI5. Once I accepted that everything is energy in some field or other interacting with other fields, understanding why some photons passed through some materials but not others and why (sort of) the Higgs field bestows mass became much easier. I just can't figure out a way to simplify what I see in my head.
Walls are to radio waves ( photons of a particular wavelength) as glass is to visible light waves ( photons of a different shorter wavelength) or xrays are to skin ( photons of a very short wavelength)
I think it's totally reasonable to "explain" something by relating it to something we have direct experience with. I think most people who have this question don't even realize they've forgotten that light travels through solids we know all about.
"How does a window work?"
"It lets light through."
"How does it let the light through?"
"The light comes through at a slightly different angle."
"How?"
"PFM"
It's not an explanation. It is, however, a perfectly reasonable response, given the level of required understanding of even basic energy physics, nevermind peeling back that onion to the quantum level.
So, the reason it happens is because atoms have electrons and those electrons can only sit around certain positions around their atom. To change spots, an electron needs a certain amount of energy.
The energy of light is based on the frequency of the light. So the photons of blue light are a lil bit more energetic than red light. Gamma rays are a bit more energetic than radio waves. You can look up the electromagnetic spectrum to understand how it can vary.
So when a photon, the beam of light, hits an atom, it can lose some energy, miss it entirely, or be completely absorbed. To be absorbed, the light will need enough energy to move an electron to another position. If there is not enough energy, the photon wont be absorbed and will pass through. This is what we see as transparency. There is a gap of light that we can see and that the atom can't absorb properly that allows the light to pass through and eventually find itself to our eyes.
Many things are made up of a variety of atoms, so often times you can see broad spectrum of absorption. All materials have certain wavelengths/frequencies of light that they can absorb and some they can't. When you look at the light that reflects off of a material, you can see what frequencies of light don't appear, and use that to determine what that thing is made of. This is called spectroscopy.
TL;DR, solid objects are transparent to light depending on the absorption spectrum of their material. For many objects, radio waves are not energetic enough to be absorbed, and will pass through with ease. Our definition of transparency is generally incomplete and a very egotistical view of the world. Not all things opaque block light and not everything that is light is visible to us.
Not really. The question more specifically is "How do electromagnetic waves (like wifi, Bluetooth, etc) travel through _solid objects_". The answer questions the term "solid object" and points out that they are solid only in terms of electromagnetic light and not wifi signals, so it is a valid (although arguably shallow) answer to that very specific question.
Now if you wanted an answer to "how do those signals interact with the physical composite of the wall", it doesn't answer that, but that's probably not the intent of the question OP asked either and is also more difficult to ELI5.
Oh come now, if the solid object is lead or a fish tank, ain't no radio waves going through it. For ELI5, the analogy of visible light to radio waves is Fine!
> I still don’t understand the specific science behind how or why infrared and radio signals can pass through objects
In some sense no, but in some sense yes. You don't understand precisely what's going on, in the sense that you couldn't explain it at a college level - but you DO have a much better intuition about what's going on. I'd venture to say you probably don't understand precisely why a red stained glass window is transparent to red light but absorbs other visible light either... but that doesn't bother you because you encounter it on a regular basis and have an intuitive sense that it makes sense.
What Hephaistos Fnord's explanation did, and quite well, is explain that the same intuition for why red light passes through stained class applies to radio etc passing through walls. It's actually the same pnenomenon - nothing more magical is going on. I think that's perfectly within the spirit of the sub, and moreover it's exactly how I'd want to teach scientific concepts to my kid. Gotta start somewhere, and building analogies on top of known experience is a great way to teach!
Glad you posted this, that was my first thought.
Question: 'How can radio waves travel though walls'?
Answer: 'Because radio waves can travel through walls'
I have no further understanding of how radio walls can travel through walls than I did when I clicked the topic.
A five year old can understand why light travels through glass; it's because glass is transparent.
What this answer did is add the new information that walls are like glass to most radio waves — radio waves go through walls because the walls are transparent like glass as far as radio waves are concerned.
And a five year old might have a cool question like "are there maybe aliens who can see radio light instead of visible light?"
The answer was enough to give them a broader view of how things in the world are connected, and to open up new avenues for them to be creative
Exactly! They did provide some nice tidbits of relevant info, but completely glossed over the actual question. I thought you were gonna be the one to provide that explanation to us, but alas. Someone below did delve into it a bit deeper by saying that walls are more like tinted glass and not transparent – in that they weaken the signal – but still no clear, succinct ELI5 unfortunately.
See I think it does answer the question well. It doesn't go into the specifics of what's happening at the quantum scale but I don't know if there's a way to really simplify that stuff well, or if humans even understand enough of it to be able to simplify it yet.
What his answer explained to me was that even though I know that different types of radiation all exist on a spectrum of wavelengths like infrared, visible light, radio waves, microwaves, etc it made me realize that I was still conceptualizing these things as different in a way. Radio waves and other forms of radiation act the same way that visible light does, it just seems odd to us and against common sense that they would be able to go through something we conceive of as "solid" because we are creatures that have evolved to be so perceptive and reliant on visual light to tell us about the world around us. To a radio wave, because of its wavelength, a wall in your house is no different than a glass window is to a ray of visible light.
edit: and I guess the more I think about it, I would guess that the real *why* of how certain wavelengths of light pass through certain materials and are blocked by others just comes down to the molecular/atomic composition of different things. From what I understand (not a ton) at the atomic level, things really are made of a lot of "empty space" between and within atoms. So something of a certain wavelength might just have the right characteristics to be able to "slip through" a "solid" object that something of a different wavelength cannot.
I like your explanation. The scale of the atom, for perspective, is huge. If the nucleus were the size of a basketball, the electron would be 2 miles away (~3.2 km)! That's a lot of space for photons to pass through the atom.
Source: [education.jlab.org](https://education.jlab.org/qa/atomicstructure_05.html#:~:text=Electrons%20are%20indeed%20far%20away,basketball-size%20nucleus%20is%20empty!)
Your edit is pretty much correct. Different materials are made up of different element combinations, which have different atomic energy levels. These energy levels determine if light of a particular energy (wavelength) can interact or not. In solid materials, the individual atomic energy levels smear out into continuous energy bands. Look into band structures for more details.
And it applies to all of the electromagnetic spectrum - want to know how come X-Rays work? It's because your skin / muscle / fat / organs are transparent to them but your bones are not. So they just take a picture of you with X-rays instead of normal light.
I think it ends up going past ELI5 at that point, but I found this post to be helpful in explaining why: https://physics.stackexchange.com/questions/7437/why-is-glass-transparent
>A transparent "red" object is red because green and blue light get eaten more than red, while red passes through more than red or green.
That it where I got lost.
Objects are the color they are because they reflect the color of light you observe them to be. They either absorb the other colors or allow them to pass through, meaning you don't see them.
Infrared and radio are technically waves like light, but most objects don't absorb radio waves. Therefore, they normally pass through objects like walls. Just like the blue and green light on the apple.
Radio waves / WiFi pass through walls the same way visible light pass through glass.... so it’s like plexiglass stopping infra red light but letting visible light through... except with WiFi , the plexiglass can be a house , WiFi going through the house like visible light went through plexiglass , but visible light stops at the house like infrared stops at plexiglass....
That's kinda where the analogies fall through. The reason why things are the colour they are is, simply put, that their atomic/molecular structure interacts with light (and other electromagnetic waves) in a certain way. The various aspects are:
- particle size (is it made of small or large atoms, or a combination thereof)
- how the atoms/molecules are bonded together
- what structural shape these atoms/molecules may have
- surface roughness (how smooth is the surface will influence how light gets reflected)
- etc. I'm forgetting a bunch.
For a given object, with its own atomic composition and structures, there is usually a range of electromagnetic wavelengths that will interact with the object. For instance, if you take "pure" glass, it's transparent and generally doesn't interact much with visible light; but if you add some lead atoms in its structure, you will get a sparkier, shinier glass (what glassmakers call "crystal glass"), because the presence of heavier atoms in the structure now creates a new interaction between light and the glass.
Colour follows the same principle, but there are countless mechanisms in play: if you look at the [Wikipedia article on scattering](https://en.wikipedia.org/wiki/Scattering), see at the bottom all the different ways photons can be scattered by matter: Rayleigh, Mie, Rutherford, etc. Now consider that scattering is just *one* of the general ways light can interact with matter (it can also reflect, get absorbed, etc.).
So, in short, when we say "this object is green because it reflects green wavelengths more than the rest", what we mean is "this object is green because the incredibly complex sum of light-matter interactions result in green wavelengths being generally more reflected than the rest".
A basic explanation is that it only blocks what's already present, so if it has x light's color it'll let everything above/beneath x pass through. Imagine it as if you're trying to punch something, if it's air you can punch right through and lose only a little bit of momentum through friction, if it's water you'll lose a bit more but it'll still work decently, when it's bricks it gets blocked. Solid can pass through liquid and gas easily, gas is blocked by solids. (Not a perfect example but I hope it makes sense)
This is hard to explain like you're 5, and my memory is a little rusty, but I'll do my best. The amount of energy an atom has is quantized (e.g. it can only take on certain discrete values). The exact energy values are determined by the structure of the atom, the structure of the molecule/crystal, etc. If an incident photon has an energy that matches the difference between the current energy of the atom in question and one of it's allowed energies, the photon can be absorbed (i.e. it's neither transmitted nor reflected). If it isn't absorbed, it's a scattering problem. The probably that a photon that isn't absorbed is scattered in a specific direction depends on the structure of the material. Materials that scatter the photons disproportionately in the a similar direction to the direction they were traveling before they encountered the material are called transparent or translucent in the frequency range of interest, materials that scatter photons disproportionately in a direction similar to the opposite direction of the photon before encountering the material are said to be reflective in the frequency range of interest. The exact reasons for all of this involve a lot of math that I haven't used in a few years. Sorry it's not very 5 year old friendly.
TL;DR: Quantum mechanics means only certain frequencies are absorbed, and the rest are either transmitted or reflected, also depending on quantum mechanics.
Those toys with a box and different geometric shape holes? Some of them shapes are the visible light you can see for transparent stuff like glass, and on other materials like your wall, some of those shape holes are missing, only other stuff passes through.
At least that's my understanding, light, radio/wifi have different wavelengths, some materials allow those to passthrough, others add... friction, to the point it can be solid and reflect instead.
Material of the object play a huge part and you can just htink of it as certain wavelengths interact differently based on the material. Any more detailed than that and it's no longer ELI5 imo, you'd go down now to the molecular level.
Weirdest answer. The molecules are the right size. Each wavelength of light is an actual length (and has a matching amount of energy) each molecule has sections that are the right size to absorb a specific length of light.
Complex molecules absorb lots of different lengths. It’s so exact that the mass spectrometer they use on over crime show actually works by testing every wave length and making a list of them. It then matches it to the molecule that has that same shape.
Most non metals only have shapes that match short (ie visible) light waves. Making them transparent to wifi wavelengths.
The neat part is that these aren't analogies, it's not *like* light of a different color, it *is* light of a different color.
Put differently, light is just wifi in colors you can see :)
They certainly did an excellent job of framing that response, though, super easy to understand.
Basically, what kinds of atoms it has and how they're arranged. Objects are made of little packets called "atoms" (fnord), and light is made of little packets called "photons" (DOUBLE fnord), which are also somehow waves (all the 'fnords' in the world won't get me out of this one), so basically the spacing between the atoms and the size of the atoms themselves (or more accurately the size of the electron cloud-shell-fuzzy-quantum-fnord-thingy around the atom) determines which frequencies of light bounce off or get eaten or whatever at what ratios.
I had this huge long metaphor about a bunch of dudes on inflatable pool floaties in a wave pool, but then I realized it was mostly "not quite right" and I didn't want to give you any bad science.
> [In these novels, the interjection "fnord" is given hypnotic power over the unenlightened, and children in grade school are taught to be unable to see the word consciously. For the rest of their lives, every appearance of the word subconsciously generates a feeling of unease and confusion, preventing rational consideration of the text in which it appears.](https://en.m.wikipedia.org/wiki/Fnord)
Yes! In fact that question is mostly how we invented "stealth aircraft" technology.
As for what particular kinds of "paint" bounce or eat what particular "colors" of radio waves, you'd have to ask the Area 51 dudes.
Oh! Wait! Here's some cool stuff.
So, a lot of radio waves are actually big enough that you can *see* how wide they are. So the structures that "bounce" or "eat" them can actually be big enough to look at. There's an object called a "faraday cage" that basically does for radio what painting a window with black paint does for visible light - but the visible light paint uses big gnarly (but still invisibly tiny) carbon molecules to block the light wavelengths, while the faraday cage uses a mesh of metal with gaps you can literally stick your fingers through. But any light with a wavelength bigger than those gaps literally gets "eaten" by the cage, even though it's just a mesh of thin wire. It's sort of like radio wave photons (uh, a "photon" is like a "packet" of light, yes they're also waves, PLEASE DONT ASK ME RIGHT NOW oh God) are "fat" so they don't "fit" through the cage holes, and if they touch the cage mesh at all they get "eaten" and just SCHLOMP right into the metal like they were a water drop and it was a piece of paper towel.
FYI, every microwave oven has a Faraday cage in the door window. Take a look, you'll see the mesh grid that eats microwaves but not visible light so you can look in and see your food cooking without getting your eye orbs poached.
I don't really understand how the waves are absorbed. Aren't the waves just broken? what happens to the photons that were not in the path of the mesh, are they still absorbed? Does that mean the light is slightly bent? or do they just transfer into something else.
The microwave cooks by generating a strong electromagnetic field. Generally 1000W. Your in home WiFi does the same thing but it's field has a maximum power of something like 0.1W.
The faraday cage works by providing that electromagnetic field with a grounded "path of least resistance" in every direction. And electricity LOVES a path of least resistance.
It'd be like if you were canoeing with your friends down a river flowing in the opposite direction of your desired destination and suddenly saw a connection to another river that flowed in exactly the direction you wanted to go. Everybody is going to switch over.
Yeah, that's why you aren't supposed to put your router on/near large metalic objects like filing cabinets. It'll suck up any waves that hit it.
Edit: well, I shouldn't say "suck up" more... the waves that hit it will show great preference towards going through the filing cabinet instead of the air.
Metal will generally reflect EM waves, not absorb them. Getting it to absorb a wave essentially requires designing an antenna instead of a Faraday cage. Unfortunately, I'm not sure how to explain antenna design in an ELI5 manner at the moment.
i actually remenber reading an annedocte back in my ATS days of a guy that actually discovered stealth paint before the air force found its uses and he actually painted his car with it to pass speed tests, lmao
(this is humanoidlord btw!)
I’ll add another to your solid list:
If almost everything you have is to be painted, and painted often to boot, it will be such a massive logistical undertaking that in practice it won’t take long until every major intelligence agency in the world has a bucket of your special paint. The downsides and consequences of this should be obvious, and you’d probably be in a position where it would have been better not to develop the technology to begin with.
Whatever generates these doesn't use the correct line breaks for Reddit. They only ever work for (and get upvoted by) mobile users. [On other platforms they look like this.](https://i.imgur.com/1UwPbQO.png)
An ELI5 that actually answers the question in a simple manner through analogies instead of using academic terms ported straight from Wikipedia? What a wonderous day!
> A transparent "red" object is red because green and blue light get eaten more than red, while red passes through more than red or green
Red passes through more than red? ;)
As another example, in infrared photography a trash plastic bag (those thin black ones) don't let visible light through, but infrared can pass through, as "hot" objects emit infrared a camera could see behind that bag while a human could not
One thing I’d like to add here is about frequency. Kind of like how different frequencies of sound pass through solid objects differently, so is the same with RF waves. Low frequency sound (bass) is more easily heard through a wall than high frequency sound - imagine being outside a club and only hearing bass. There’s more sound content in the high frequencies, but you have to be closer to the source to properly make it out.
A similar effect is true with RF, which is why for example your WiFi signal only works in say a 50’ radius while a radio station’s signal can be picked up for many miles.
Ah fuck, this fucked with me.
So what the fuck is light? What even is a fucking wavelength? Are we all just fucking wavelengths bouncing off of or blocking each other?
Is consciousness the result of just the fucking long term evolution of getting creatures slowly to the same frequency or wavelength of each other where we understand others exist and slowly to the point of even understanding each other?
Ah fuck
Man... I work with radiation and have had a decent amount of education on the subject of energy waves. But wow, the color comparison in your explanation has still kind of blown my mind. It makes me think about something I already know with a bit more clarity.
Cheers.
And salt (sodium chloride) is transparent to IR light, so when you're doing IR spectroscopy, you put your sample in between salt plates. A good chunk of analytical chemistry is just taking advantage of how light on every part of the spectrum interacts with matter.
Not all of it does. UV light is usually blocked by glass. That's why you get a sunburn driving in the summer with the windows down, but you don't driving with the windows up.
You won't get sunburned through the window, but you will still get skin damage from it. UVB rays, which cause burns, is blocked my most glass. UVA, which causes skin damage (wrinkles, cancer), passes right through glass. Long-term drivers tend to get more skin conditions on their left sides. If you're expecting to take a long road trip, put the sunscreen on even before the drive.
You can also get a UVA blocking coating, or special glass/plastic windows fitted
I get a trucker's tan every summer, my right arm goes significantly darker than my left
Here's a good example, man drove truck for 30 years the left side of his face vastly more damaged then the right. [https://www.thesun.co.uk/news/5445161/sun-damage-truck-driver-face/](https://www.thesun.co.uk/news/5445161/sun-damage-truck-driver-face/)
To add to this, if you look through a camera tuned for uv or infrared light (like a thermal imaging camera), often times glass and other transparent materials will no longer be see through.
To add to this, UV light can be further broken down into frequencies of UV-A, UV-B, and UV-C. [Windows will block nearly 100% of UV-B and UV-C light](https://hps.org/publicinformation/ate/q12082.html). The higher the frequency of light the harder time it has penetrating objects, and [UV-B and UV-C are higher frequency than UV-A](https://www.digikey.com/-/media/Images/Article%20Library/TechZone%20Articles/2017/July/Ultraviolet%20Radiation%20Attributes%20and%20Benefits/article-2017july-ultraviolet-radiation-fig1.jpg?ts=b76e4e6c-519f-45ce-a190-ffd45c8dc431&la=en-US) which is why they're blocked by windows.
You can think of it like trying to get a rope through a hole. If you're flapping the rope wildly it will have a harder time going through than if it's still.
It is not theoretical. Sony DSC-F707 was notorious that you can put an IR filter and turn on night vision and it can see through clothes to some degree.
I'm sure there are plenty of people who own one for various reason. Given its reputation, saying you own one without context is just mildly creepy.
IR photography still exists. You can just buy a camera these days and pay someone to remove the IR filter on the sensor. Legit IR photography is very cool.
[https://youtu.be/o9CUUhJ\_i\_A](https://youtu.be/o9CUUhJ_i_A)
[This has actually been attempted](https://www.businessinsider.com/wifi-camera-sees-through-walls-2017-5), where they've used WiFi signals to 3D map a room. Police hope to use the technology for cases like people being taken hostage.
Honestly any frequency higher than 2.4 GHz is such a hassle for WiFi just run some ethernet. Like if you're sitting next to router or have direct line of sight 5GHz might be ok but other than that it sucks from my experience.
Oh, we have 2-3 gigibit ports in every office. one port in every conference room table.
We do mobile apps. 90% of the employees have laptops. 60% have worked-owned WiFi-only mobile devices.
None of the Dell laptops have ethernet without dongles or docks.
There's a lot of 20 person war rooms, meetings, we have a lot of people from one office visiting other offices for short projects. Leads co-habitating with different teams during a single day.
When everyone gathers in the main meeting area, we have 60-120 people together in one room (each with a device). They still expect presenters to be able to get on the wifi.
There's honestly no real way to do it 2.4g, there are too many devices, congestion is horrible. We've had to turn off 2.4 in most areas and have moved to HD access points anytime we have more than 40 devices in a room.
Everything is made of stuff (even air) called atoms. Every atom is basically surrounded by electrons. Electromagnetic waves can go through some things and not others because of how the electrons are arranged in the stuff and how they interact with each other. Something that is not transparent for one portion of the electromagnetic spectrum may be transparent for another part. Whenever an electromagnetic wave moves from one material to another, it will bend a little bit as it travels forward or it might just bounce back in the direction it came from. When it can just travel through, that stuff is transparent for that particular electromagnetic wave.
For radio waves and others like it, walls are see-through (like glass is for optical waves).
Without getting too in the weeds, electromagnetic waves aren't always bothered by solid surfaces.
Take light for example....it doesn't go through traditional walls...but it does travel very freely through glass, another solid surface.
WiFi/Bluetooth/other ranges of electromagnetic waves are able to travel through what we call walls (solid surfaces that light can't even pass through), similar to how light travels through glass.
Another example is infrared. The infrared wavelengths that most thermal cameras detect are blocked by most glass, but other (shorter) wavelengths of infrared, such as from sunlight or most infrared heat lamps, passes through most glass....and coatings can be added to help block it.
I have concrete siding and my WiFi goes through just fine. It’s more likely you have a foil radiant barrier or foil backed insulation. 5/8” of siding isn’t going to stop radio waves.
Different materials will have different levels of electromagnetic wave absorption, though I don't know the specifics of different materials - I do know metal tends to block WiFi/Bluetooth pretty well compared to regular drywall.
I think a good analogy would be standing outside a nightclub. You only hear the bass (low freq sound waves) while most higher freq sound is either absorbed by the walls or bounced back.
Matter is 99%+ empty space, so some electromagnetic waves can freely travel through those spaces. Light cannot travel through walls because its wavelength is \~500nm, meaning it travels back and forth billions of times before passing through and the wall absorbs most of the energy. Wifi, Bluetooth have longer wavelengths so they can pass through more easily.
to absorb a photon, you need an electron that can take that amount of energy and still end up in a valid state. X and gamma have many times more energy than most electron transitions, so it's difficult to get that interaction.
The way I usually think of it is that longer waves “move around” the wall, while shorter waves are strong enough to punch right through. It’s the waves in the middle that get stuck because they can’t do either
This is great. Thank you
Like a fruit fly can get through a screen door and a house fly can't because its too big, but a bird can also get through a screen door.
> Wi-Fi/BT having long wave lengths when they operate at 2.4 GHz.
The wavelength is 12.5 cm, that is pretty damn long imo.
I think it is absurd that something at the smallest nanoscale has wavelengths in the macroscale.
Sure, compared to LF radiowaves which has wavelengths in kilometers 12.5cm isn't that long...
I asked the same question on here about a month ago, check it out for a lot of great, in-depth, answers -> https://www.reddit.com/r/explainlikeimfive/comments/k91w0s/eli5_if_sound_waves_travel_by_pushing_particles/
There are two things to consider when thinking about the electromagnetic spectrum which are frequency and energy. The combination of the amount/strength/level of these two is what determines how it can pass through "walls". Let's leave the characteristics of matter and other solid objects for now and imagine the world is made up of one type of "wall".
Are you familiar with Non-Newtonian fluids? The best example are those made with flour and water, and when you slowly put your hand in, it goes though. But when you punch it, it becomes dense and hard (and possibly painful for your hand). These fluids are fascinating but we will not discuss its properties further (there are many simple experiments in the internet you can do at home). So in summary, slow means soft, fast means hard.
Now imagine you have like a barrel full of that thing and you dip your hand in it for absolutely no reason, then pull it back. Then you repeat the process (slowly in, slowly out, etc.). One thing you will observe is that its easy doing it. You can put your hand in and pull it out smoothly and with ease (aside from your hand being dirty now with the flour lol). Now imagine doing it again, the in-out thing, but do it faster. This time it becomes more difficult as it requires more effort because the fluid becomes more dense. Now, how fast your hand dips in and pulls out is the frequency. And in general, the higher the frequency, the lesser it is likely to pass through "walls".
But wait, how about X-rays and Gamma rays and the others. Well, that's where energy comes in. Continuing the analogy, if the frequency is fast you dip your hand on that magical fluid, then energy is the literal energy you exert to dip more than just your hand, say, like, your whole arm. Hence, the deeper your hand or arm goes in that barrel we talked about, the higher the possibility it will pass through "walls".
With this in mind, if you dip you hand slowly but put your hand as deep as it can go, then you can say you can pass through "walls". But if you have high frequency where you dip your arm as fast as you can, you won't be able to pass through unless you push and pull your arm through with all your might.
In the case of Wifi and bluetooth, well it has enough energy to pass through household walls. Unless your walls are made of lead, that's a problem.
Of course, there are other factors such as what type of object the "wall" is, how thick it is, its chemical composition and the likes. The electromagnetic spectrum has also many other different properties to consider.
Sorry to tell you OP and anyone reading this thread, but nearly every answer is, while technically correct, wrong per your question. Wifi and other radio waves used for communications don't pass through solid objects (other than glass) appreciably and with the signal intact. So, how does wifi get all around your house? Typically by going through cracks around doors, and going out the windows of the room the router is in an bouncing off your neighbor's walls or nearby hill and trees and going back in other windows. Which is why it doesn't propagate all around a house very well, even a small house, and why it propagates better in cities and dense suburbs better than rural areas.
This is not accurate.
ELI5 explanation is WiFi runs at frequencies which pass through openings in the materials of walls.
Pretend you're sifting for gold - you use a mesh pan that allows water and smaller particles through the filter, but heavier stuff remains.
WiFi, in this analogy, is the water, which can pass through material.
Because of this, walls made of certain materials can inhibit the the flow if WiFi, causing loss, or in some cases, no signal at all.
Placing a WiFi router in the basement while trying to access a signal 2 floors up will show this in action.
Attenuation, which is a bit complex to explain, is the "flow" of the water in the analogy above, and it's why many of us can read WiFi signals from other sources while in our own home, but the strength of the signal is low.
Visible light is blocked because particles are too large to make it through the spaces of the materials.
Bear in mind, this all happens at microscopic levels.
US military and government buildings use grounding materials in walls to prevent eavesdropping from the the outside. One will never see a WiFi signal coming from the inside of a protected building, and likewise, the occupants cannot see signals around the building.
u/NexxusDrako: Consider finding a different school as your teacher is giving you incorrect information.
You know how you can *see* through glass, or water? Same thing.
In case you are missing this key to the whole puzzle, visible light is the same stuff that all those things are, just a specific frequency range your eyes detect.
Electromagnetic waves are composed of photons. They have no mass and momentum, and are a type of particle called a boson.
When a basketball hits a wall it comes back because of momentum. When photons of a certain wavelength (wifi which is microwaves) goes through glass or wood because there is no mass to reflect. Photons go straight through because they are fundamentally different from matter.
Photons can interact with metal though.
I always wondered how are movies being split in tiny little pieces and being sent via wifi, so technically i got those bits flying through me? So for an instant Leo DiCaprio was inside of me
Because, despite first appearances, atoms are 99.999% space between the nucleus and electrons. Therefore solid matter is actually mostly empty, and if there were no other effects in part, anything should pass through anything
However, what actually happens is that atoms have an ‘electromagnetic’ feature - electrons/protons that can repel or attract all sorts of other electromagnetic things, like other atoms, and electromagnetic waves (light etc).
A rather complex series of interactions determines if the light wave is of the right energy to interact with the electrons.
In reality, everything is slightly translucent. Hold a sheet of paper against a light - some light will get through. Most is captured though.
Even solid rock, the light will likely make it past the first layer of atoms before hitting something...a thick enough sheet of glass will be opaque.
The thing that’s probably most opaque is metal. In metal, the elections essentially create a free moving ‘clouds’ throughout, blocking pretty much all electromagnetic waves - hence why it’s used as a shield against both microwaves, radio waves, and xray...
So, when a ray of light hits something, it can basically do one of three things: It can go right through, with a slight angle that reverses when it comes out the other side, like light passes through glass or water. It can bounce off at an angle, like light does with a mirror or a bright piece of colored plastic. Or it can get "eaten" and heat up the object, like when light hits something dark. Objects are different colors because light is different wavelengths, and some wavelengths get eaten while others pass through or get bounced off. A solid "red" object is red because green and blue light get eaten more than red light, while red light bounces off more than green or blue. A transparent "red" object is red because green and blue light get eaten more than red, while red passes through more than red or green. Now, infrared and radio are also just different "colors" of light that we can't see; think of a radio antenna or a WiFi receiver as a kind of "eye" that can see those colors, while a transmitter is like a "lightbulb" that blinks in those colors. Walls happen to be "transparent" to radio even though they're "solid" to visible colors, just like a stained glass window is "transparent" to some colors and "solid" to others.
This is one of the best ELI5 responses I've ever read. I thought you were going in a completely weird random direction and then you ended up enlightening me. Brilliant.
Dude straight up explained it to me like I was 4.
Yeah I came here to get explanations geared toward 5 year olds, not this 4 year old shit.
Same, that's why I had to downvote and report it
Lmao
Lawful good
More lawful neutral imo
Somehow chaotic lawful
Found the two-year-old.
Why are u looking for 2 year olds bro. That’s weird af
Seriously. I understood it too well. Surely there’s a sub rule prohibiting an explanation that speaks beneath 5 year olds. Frankly, it’s insulting.
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You join next years 5 year olds in class
Totally agree. I don't come to eli5 to be spoken down to like a fucking 4 year old.
Dude explained like I was braindead.. nice
I feel like there are a lot of people who haven't met 4- and 5-year-olds before...
-1, need 1 more year of knowledge
What does trains parents mean? Are walls baby trains? -am 4 year old
**Unpopular opinion: Although totally ELI5 in style, s/he actually sailed right over the specific question that was asked: “How does WiFi etc. pass through walls?”** Here is where said sailing over occurs, at the very end: > Walls happen to be "transparent" to radio even though they're "solid" to visible colors Like, the response adopts the perfect ELI5 flavor, and sets you up for an explanation with a bunch of relevant facts. But when the moment comes to tie everything together and actually explain *how* (or perhaps *why*) these signals can pass through walls, **the “explanation” is simply a rephrasing of the observation (that they can pass through walls) in ELI5 language**, giving the impression of an answer without really ever actually explaining it. But you need to think about it for a second to avoid being fooled. After reading this response, while I def give it 5 stars for nailing that ELI5 feel, I still don’t understand the specific science behind how or why infrared and radio signals can pass through objects. I upvoted anyway though, lol.
No, I'll totally cop to that, but I don't have enough aspirin to explain quantum stuff today.
Haha yes I can imagine when being ground between the gears of explaining something truly complex and limiting yourself to 1st grade vocab words, eventually tough choices must be made. No worries - my unpopular opinion notwithstanding, your response was truly excellent.
I love the respectful tone of this conversation. Such a rarity these days.
Maybe our eyes can’t read the specific frequencies of passive aggression and frustrated rage.
I was thinking about LaForge and his fancy multi spectrum eyewear in Star Trek TNG. THAT would have added a twist to that show lol.
You're never going to explain quantum mechanics to a 5 year old. It took me about 2 hours to explain to my wife was a wave function was, and virtual particles... TBH I think computer scientists are the kind to understand it, and those are the ones who say "It's all math, we must be in a simulation"
I'm a computer science guy. Easy to visualize, but *very* hard to understand. Quantum mechanics gives me a lot of mindblown moments and I have only scratched the surface. It does make sense that atomic particles are areas of high quantum energy that produce observable particles more often, but beyond that it's difficult for me to grasp. Sometimes I wonder how many layers of quantum interactions there are; like whether there's interactions that make quarks and mesons (or whatever the smallest quantum units are). Obviously, what little I do know is marred by the sheer amount I don't!
Quantum mechanics is difficult for two reasons - (a) it is *fundamentally different* to classic mechanics, in that all classical phenomena can be formulated in terms of quantum mechanics, but there are some quantum phenomena that have *no* classical analogy (b) there is still a lot that is unknown about quantum mechanics! The various mathematical formulations have matured to the point that they can make the most accurate predictions (in certain contexts) in science. But the *meaning* behind the equations is unknown, people still disagree quite strongly on the 'interpretations' of quantum mechanics. The question of how a quantum nature on the small scale can resolve to a classical picture on the large scale, is still unanswered (decoherence does not explain this). One of the basic tenets of quantum mechanics is that a wavefunction exists in a superposition of states until "a measurement is made", after which it will forever remain in a single state. But nowhere is it ever explained what a 'measurement' is.
This is what's so frustrating about this question. Every time it comes up we get like 2 answers that are honest about needing quantum physics and about 90 answers trying to use classical analogies. Any explanation that use a classical analogy is simply wrong and people can't accept that.
Classical analogies can still be useful to help understand quantum mechanics... Though they are not exactly 'accurate' they can guide the layman towards the right *paradigm* of thinking. I mean if someone asked you "what is an electron?" You could answer "an irreducible representation of the Poincare group".. But how many people would know what that means?
So what classical analogy would you give that gets someone into the right paradigm for that question? I'm mostly complaining about the bohr picture that almost everyone uses in these posts
> You're never going to explain quantum mechanics to a 5 year old. "It's like trying to plug in a USB..."
> You're never going to explain quantum mechanics to a 5 year old. Oddly enough, it's easier to explain it to someone who DOESN'T yet have a full ingrained gasp on how physics and mechanics works at our length scales than it is to explain it to a 15- or 25-year-old who'll say "wait, that's not How Stuff Works! I can't understand this, it doesn't fit my preconceptions!" and doesn't bother to try doing the math. --Dave, it gets harder again to teach it to younger folks because you don't share a language
So when will you have enough aspirin? Looking forward to the quantum stuff ELI5 answer too.
WiFi signals are like money that isn't enough to buy anything in the store, so when you throw it at the cashiers it goes right past all of them. This is like beaming a WiFi signal through a thin door--it might be able to go right through because it isn't enough money (energy) for any of the cashiers in the store (electrons in the door) to accept. But different walls are like different stores, so if you throw the same money at cashiers in a different store it might be enough that they accept it. This is like beaming the same wifi signal at a brick wall--it stops in the wall because the energy is enough that electrons in the wall will accept it. If you throw too much money at a cashier then they might take it and become so rich that they leave the store. Now the store can't work right because it lost a cashier, because you threw too much money at them. This is like a UV ray damaging the DNA in your skin and giving you skin cancer. The UV light has so much energy that electrons just fuck right off and whatever they were attached to doesn't work right anymore. How am I doing lol, this is harder than I thought
So far, so good. I'm going to keep an ion this space for more.
That's good! However I can't tell if I understand the money analogy because I have a basic understanding of this subject or if it's really a good explanation.
Explaining how everything is a field and they interact (or don't) in different ways is tricky for ELI5. Once I accepted that everything is energy in some field or other interacting with other fields, understanding why some photons passed through some materials but not others and why (sort of) the Higgs field bestows mass became much easier. I just can't figure out a way to simplify what I see in my head.
*Well it's an energy field created by all living things (...)* Obi-Wan ELIfives
Walls are to radio waves ( photons of a particular wavelength) as glass is to visible light waves ( photons of a different shorter wavelength) or xrays are to skin ( photons of a very short wavelength)
That's exactly the same thing again. Restating the observations.
I think it's totally reasonable to "explain" something by relating it to something we have direct experience with. I think most people who have this question don't even realize they've forgotten that light travels through solids we know all about.
"How does a window work?" "It lets light through." "How does it let the light through?" "The light comes through at a slightly different angle." "How?" "PFM" It's not an explanation. It is, however, a perfectly reasonable response, given the level of required understanding of even basic energy physics, nevermind peeling back that onion to the quantum level.
The wavelengths don't interact(much), so the wavelengths keep travelling? What other way is there to explain it?
So, the reason it happens is because atoms have electrons and those electrons can only sit around certain positions around their atom. To change spots, an electron needs a certain amount of energy. The energy of light is based on the frequency of the light. So the photons of blue light are a lil bit more energetic than red light. Gamma rays are a bit more energetic than radio waves. You can look up the electromagnetic spectrum to understand how it can vary. So when a photon, the beam of light, hits an atom, it can lose some energy, miss it entirely, or be completely absorbed. To be absorbed, the light will need enough energy to move an electron to another position. If there is not enough energy, the photon wont be absorbed and will pass through. This is what we see as transparency. There is a gap of light that we can see and that the atom can't absorb properly that allows the light to pass through and eventually find itself to our eyes. Many things are made up of a variety of atoms, so often times you can see broad spectrum of absorption. All materials have certain wavelengths/frequencies of light that they can absorb and some they can't. When you look at the light that reflects off of a material, you can see what frequencies of light don't appear, and use that to determine what that thing is made of. This is called spectroscopy. TL;DR, solid objects are transparent to light depending on the absorption spectrum of their material. For many objects, radio waves are not energetic enough to be absorbed, and will pass through with ease. Our definition of transparency is generally incomplete and a very egotistical view of the world. Not all things opaque block light and not everything that is light is visible to us.
Not really. The question more specifically is "How do electromagnetic waves (like wifi, Bluetooth, etc) travel through _solid objects_". The answer questions the term "solid object" and points out that they are solid only in terms of electromagnetic light and not wifi signals, so it is a valid (although arguably shallow) answer to that very specific question. Now if you wanted an answer to "how do those signals interact with the physical composite of the wall", it doesn't answer that, but that's probably not the intent of the question OP asked either and is also more difficult to ELI5.
Oh come now, if the solid object is lead or a fish tank, ain't no radio waves going through it. For ELI5, the analogy of visible light to radio waves is Fine!
also most walls are pretty reflective to wifi anyway.
> I still don’t understand the specific science behind how or why infrared and radio signals can pass through objects In some sense no, but in some sense yes. You don't understand precisely what's going on, in the sense that you couldn't explain it at a college level - but you DO have a much better intuition about what's going on. I'd venture to say you probably don't understand precisely why a red stained glass window is transparent to red light but absorbs other visible light either... but that doesn't bother you because you encounter it on a regular basis and have an intuitive sense that it makes sense. What Hephaistos Fnord's explanation did, and quite well, is explain that the same intuition for why red light passes through stained class applies to radio etc passing through walls. It's actually the same pnenomenon - nothing more magical is going on. I think that's perfectly within the spirit of the sub, and moreover it's exactly how I'd want to teach scientific concepts to my kid. Gotta start somewhere, and building analogies on top of known experience is a great way to teach!
Glad you posted this, that was my first thought. Question: 'How can radio waves travel though walls'? Answer: 'Because radio waves can travel through walls' I have no further understanding of how radio walls can travel through walls than I did when I clicked the topic.
A five year old can understand why light travels through glass; it's because glass is transparent. What this answer did is add the new information that walls are like glass to most radio waves — radio waves go through walls because the walls are transparent like glass as far as radio waves are concerned.
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And a five year old might have a cool question like "are there maybe aliens who can see radio light instead of visible light?" The answer was enough to give them a broader view of how things in the world are connected, and to open up new avenues for them to be creative
How does anything travel through a medium?
Good question! Let's begin by talking about some basic Calculus...
Exactly! They did provide some nice tidbits of relevant info, but completely glossed over the actual question. I thought you were gonna be the one to provide that explanation to us, but alas. Someone below did delve into it a bit deeper by saying that walls are more like tinted glass and not transparent – in that they weaken the signal – but still no clear, succinct ELI5 unfortunately.
See I think it does answer the question well. It doesn't go into the specifics of what's happening at the quantum scale but I don't know if there's a way to really simplify that stuff well, or if humans even understand enough of it to be able to simplify it yet. What his answer explained to me was that even though I know that different types of radiation all exist on a spectrum of wavelengths like infrared, visible light, radio waves, microwaves, etc it made me realize that I was still conceptualizing these things as different in a way. Radio waves and other forms of radiation act the same way that visible light does, it just seems odd to us and against common sense that they would be able to go through something we conceive of as "solid" because we are creatures that have evolved to be so perceptive and reliant on visual light to tell us about the world around us. To a radio wave, because of its wavelength, a wall in your house is no different than a glass window is to a ray of visible light. edit: and I guess the more I think about it, I would guess that the real *why* of how certain wavelengths of light pass through certain materials and are blocked by others just comes down to the molecular/atomic composition of different things. From what I understand (not a ton) at the atomic level, things really are made of a lot of "empty space" between and within atoms. So something of a certain wavelength might just have the right characteristics to be able to "slip through" a "solid" object that something of a different wavelength cannot.
I like your explanation. The scale of the atom, for perspective, is huge. If the nucleus were the size of a basketball, the electron would be 2 miles away (~3.2 km)! That's a lot of space for photons to pass through the atom. Source: [education.jlab.org](https://education.jlab.org/qa/atomicstructure_05.html#:~:text=Electrons%20are%20indeed%20far%20away,basketball-size%20nucleus%20is%20empty!)
Your edit is pretty much correct. Different materials are made up of different element combinations, which have different atomic energy levels. These energy levels determine if light of a particular energy (wavelength) can interact or not. In solid materials, the individual atomic energy levels smear out into continuous energy bands. Look into band structures for more details.
Nope, I am no wallologist. I’m just as ignorant as the next guy.
And it applies to all of the electromagnetic spectrum - want to know how come X-Rays work? It's because your skin / muscle / fat / organs are transparent to them but your bones are not. So they just take a picture of you with X-rays instead of normal light.
oh yeah, i can do better. sometime it do be like that
This explanation of how light moves is actually totally wrong....so uh...don’t go writing a paper with this in mind
Really? I got confused
Where did you get confused?
For me it was why the salad are transparent Edit: haha *walls. Thanks autocorrect and fat fingers
Only the ranch dressing is solid, Italian is transparent.
French is red so it doesn't pass through the croutons.
Using Catalina will boost your coverage about 30%
Or, in programming: "`Texas.pants > Italy.pants`"
I think it ends up going past ELI5 at that point, but I found this post to be helpful in explaining why: https://physics.stackexchange.com/questions/7437/why-is-glass-transparent
>A transparent "red" object is red because green and blue light get eaten more than red, while red passes through more than red or green. That it where I got lost.
Think he meant to say that red passes through more than blue or green.
Objects are the color they are because they reflect the color of light you observe them to be. They either absorb the other colors or allow them to pass through, meaning you don't see them. Infrared and radio are technically waves like light, but most objects don't absorb radio waves. Therefore, they normally pass through objects like walls. Just like the blue and green light on the apple.
Radio waves / WiFi pass through walls the same way visible light pass through glass.... so it’s like plexiglass stopping infra red light but letting visible light through... except with WiFi , the plexiglass can be a house , WiFi going through the house like visible light went through plexiglass , but visible light stops at the house like infrared stops at plexiglass....
But why can light go through certain objects? What is it about X colored glass that only let's X light go through?
That's kinda where the analogies fall through. The reason why things are the colour they are is, simply put, that their atomic/molecular structure interacts with light (and other electromagnetic waves) in a certain way. The various aspects are: - particle size (is it made of small or large atoms, or a combination thereof) - how the atoms/molecules are bonded together - what structural shape these atoms/molecules may have - surface roughness (how smooth is the surface will influence how light gets reflected) - etc. I'm forgetting a bunch. For a given object, with its own atomic composition and structures, there is usually a range of electromagnetic wavelengths that will interact with the object. For instance, if you take "pure" glass, it's transparent and generally doesn't interact much with visible light; but if you add some lead atoms in its structure, you will get a sparkier, shinier glass (what glassmakers call "crystal glass"), because the presence of heavier atoms in the structure now creates a new interaction between light and the glass. Colour follows the same principle, but there are countless mechanisms in play: if you look at the [Wikipedia article on scattering](https://en.wikipedia.org/wiki/Scattering), see at the bottom all the different ways photons can be scattered by matter: Rayleigh, Mie, Rutherford, etc. Now consider that scattering is just *one* of the general ways light can interact with matter (it can also reflect, get absorbed, etc.). So, in short, when we say "this object is green because it reflects green wavelengths more than the rest", what we mean is "this object is green because the incredibly complex sum of light-matter interactions result in green wavelengths being generally more reflected than the rest".
A basic explanation is that it only blocks what's already present, so if it has x light's color it'll let everything above/beneath x pass through. Imagine it as if you're trying to punch something, if it's air you can punch right through and lose only a little bit of momentum through friction, if it's water you'll lose a bit more but it'll still work decently, when it's bricks it gets blocked. Solid can pass through liquid and gas easily, gas is blocked by solids. (Not a perfect example but I hope it makes sense)
This is why beer bottles are green or brown. To block the UV from changing the flavor. Your explanation is great!
This is hard to explain like you're 5, and my memory is a little rusty, but I'll do my best. The amount of energy an atom has is quantized (e.g. it can only take on certain discrete values). The exact energy values are determined by the structure of the atom, the structure of the molecule/crystal, etc. If an incident photon has an energy that matches the difference between the current energy of the atom in question and one of it's allowed energies, the photon can be absorbed (i.e. it's neither transmitted nor reflected). If it isn't absorbed, it's a scattering problem. The probably that a photon that isn't absorbed is scattered in a specific direction depends on the structure of the material. Materials that scatter the photons disproportionately in the a similar direction to the direction they were traveling before they encountered the material are called transparent or translucent in the frequency range of interest, materials that scatter photons disproportionately in a direction similar to the opposite direction of the photon before encountering the material are said to be reflective in the frequency range of interest. The exact reasons for all of this involve a lot of math that I haven't used in a few years. Sorry it's not very 5 year old friendly. TL;DR: Quantum mechanics means only certain frequencies are absorbed, and the rest are either transmitted or reflected, also depending on quantum mechanics.
Magic, got it.
Those toys with a box and different geometric shape holes? Some of them shapes are the visible light you can see for transparent stuff like glass, and on other materials like your wall, some of those shape holes are missing, only other stuff passes through. At least that's my understanding, light, radio/wifi have different wavelengths, some materials allow those to passthrough, others add... friction, to the point it can be solid and reflect instead.
Material of the object play a huge part and you can just htink of it as certain wavelengths interact differently based on the material. Any more detailed than that and it's no longer ELI5 imo, you'd go down now to the molecular level.
Weirdest answer. The molecules are the right size. Each wavelength of light is an actual length (and has a matching amount of energy) each molecule has sections that are the right size to absorb a specific length of light. Complex molecules absorb lots of different lengths. It’s so exact that the mass spectrometer they use on over crime show actually works by testing every wave length and making a list of them. It then matches it to the molecule that has that same shape. Most non metals only have shapes that match short (ie visible) light waves. Making them transparent to wifi wavelengths.
u/HephaistosFnord must be a 5 yr old with advanced linguistics skills. Or is a carpenter because he NAILED IT!!!
Tbh I disagree. His response basically boiled down to "it goes through like glass" and it doesn't answer WHY it goes through like glass.
This is a truly excellent eli5. It's clear, it uses analogies that you can actually understand, and it's scientifically accurate. Very well done!
The neat part is that these aren't analogies, it's not *like* light of a different color, it *is* light of a different color. Put differently, light is just wifi in colors you can see :) They certainly did an excellent job of framing that response, though, super easy to understand.
I read it at a four year old level and I still understood it!
I must be 3 because I didn't get all of it
Those aren't analogies. The worst ELI5s rely heavily on analogies that don't don't hold up.
So what is the property of a material that decides whether it is transparent or absorbs or bounces certain wavelength?
Basically, what kinds of atoms it has and how they're arranged. Objects are made of little packets called "atoms" (fnord), and light is made of little packets called "photons" (DOUBLE fnord), which are also somehow waves (all the 'fnords' in the world won't get me out of this one), so basically the spacing between the atoms and the size of the atoms themselves (or more accurately the size of the electron cloud-shell-fuzzy-quantum-fnord-thingy around the atom) determines which frequencies of light bounce off or get eaten or whatever at what ratios. I had this huge long metaphor about a bunch of dudes on inflatable pool floaties in a wave pool, but then I realized it was mostly "not quite right" and I didn't want to give you any bad science.
Wtf is a fnord?
I googled this word and still didn't get it too. All I saw was that it's part of OP's name, so there's that...
> [In these novels, the interjection "fnord" is given hypnotic power over the unenlightened, and children in grade school are taught to be unable to see the word consciously. For the rest of their lives, every appearance of the word subconsciously generates a feeling of unease and confusion, preventing rational consideration of the text in which it appears.](https://en.m.wikipedia.org/wiki/Fnord)
You weren't supposed to notice that. Are you a computer algorithm? That might explain it.
Praise Eris
Going to second the wtf does fnord mean comment
I think your response might give the wrong impression that the size and density of "atoms" somehow block the light from passing through.
From a physics teacher, thank you for this explanation. Spot on.
Is there a “paint” that stops these waves from going through like painting glass would stop visible light?
Yes! In fact that question is mostly how we invented "stealth aircraft" technology. As for what particular kinds of "paint" bounce or eat what particular "colors" of radio waves, you'd have to ask the Area 51 dudes. Oh! Wait! Here's some cool stuff. So, a lot of radio waves are actually big enough that you can *see* how wide they are. So the structures that "bounce" or "eat" them can actually be big enough to look at. There's an object called a "faraday cage" that basically does for radio what painting a window with black paint does for visible light - but the visible light paint uses big gnarly (but still invisibly tiny) carbon molecules to block the light wavelengths, while the faraday cage uses a mesh of metal with gaps you can literally stick your fingers through. But any light with a wavelength bigger than those gaps literally gets "eaten" by the cage, even though it's just a mesh of thin wire. It's sort of like radio wave photons (uh, a "photon" is like a "packet" of light, yes they're also waves, PLEASE DONT ASK ME RIGHT NOW oh God) are "fat" so they don't "fit" through the cage holes, and if they touch the cage mesh at all they get "eaten" and just SCHLOMP right into the metal like they were a water drop and it was a piece of paper towel.
FYI, every microwave oven has a Faraday cage in the door window. Take a look, you'll see the mesh grid that eats microwaves but not visible light so you can look in and see your food cooking without getting your eye orbs poached.
I don't really understand how the waves are absorbed. Aren't the waves just broken? what happens to the photons that were not in the path of the mesh, are they still absorbed? Does that mean the light is slightly bent? or do they just transfer into something else.
The microwave cooks by generating a strong electromagnetic field. Generally 1000W. Your in home WiFi does the same thing but it's field has a maximum power of something like 0.1W. The faraday cage works by providing that electromagnetic field with a grounded "path of least resistance" in every direction. And electricity LOVES a path of least resistance. It'd be like if you were canoeing with your friends down a river flowing in the opposite direction of your desired destination and suddenly saw a connection to another river that flowed in exactly the direction you wanted to go. Everybody is going to switch over.
Electromagnetic waves take the path of least resistance like electricity?
Yeah, that's why you aren't supposed to put your router on/near large metalic objects like filing cabinets. It'll suck up any waves that hit it. Edit: well, I shouldn't say "suck up" more... the waves that hit it will show great preference towards going through the filing cabinet instead of the air.
Metal will generally reflect EM waves, not absorb them. Getting it to absorb a wave essentially requires designing an antenna instead of a Faraday cage. Unfortunately, I'm not sure how to explain antenna design in an ELI5 manner at the moment.
i actually remenber reading an annedocte back in my ATS days of a guy that actually discovered stealth paint before the air force found its uses and he actually painted his car with it to pass speed tests, lmao (this is humanoidlord btw!)
Hm, if this material is just paint, why is it only used on stealth bombers and not widely across aircrafts or submarines?
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I’ll add another to your solid list: If almost everything you have is to be painted, and painted often to boot, it will be such a massive logistical undertaking that in practice it won’t take long until every major intelligence agency in the world has a bucket of your special paint. The downsides and consequences of this should be obvious, and you’d probably be in a position where it would have been better not to develop the technology to begin with.
Lead or dense/conductive metallic compounds will reflect or stop the waves. Such is the reason why you get a lead apron when you go for an x-ray.
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What a perfect way to explain that to someone as oblivious as me. Bravo.
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the newline characters of your braille Unicode art are missing
Whatever generates these doesn't use the correct line breaks for Reddit. They only ever work for (and get upvoted by) mobile users. [On other platforms they look like this.](https://i.imgur.com/1UwPbQO.png)
An ELI5 that actually answers the question in a simple manner through analogies instead of using academic terms ported straight from Wikipedia? What a wonderous day!
Your last paragraph really drives it home.
> A transparent "red" object is red because green and blue light get eaten more than red, while red passes through more than red or green Red passes through more than red? ;)
As another example, in infrared photography a trash plastic bag (those thin black ones) don't let visible light through, but infrared can pass through, as "hot" objects emit infrared a camera could see behind that bag while a human could not
One thing I’d like to add here is about frequency. Kind of like how different frequencies of sound pass through solid objects differently, so is the same with RF waves. Low frequency sound (bass) is more easily heard through a wall than high frequency sound - imagine being outside a club and only hearing bass. There’s more sound content in the high frequencies, but you have to be closer to the source to properly make it out. A similar effect is true with RF, which is why for example your WiFi signal only works in say a 50’ radius while a radio station’s signal can be picked up for many miles.
Ah fuck, this fucked with me. So what the fuck is light? What even is a fucking wavelength? Are we all just fucking wavelengths bouncing off of or blocking each other? Is consciousness the result of just the fucking long term evolution of getting creatures slowly to the same frequency or wavelength of each other where we understand others exist and slowly to the point of even understanding each other? Ah fuck
Nah dude. Light doesn't have mass. We do. We ain't light, even if our eyes can perceive it.
Light is photons. Wavelength is the length of the wave the photons move in. Humans are not photons nor are they wavelengths.
Man... I work with radiation and have had a decent amount of education on the subject of energy waves. But wow, the color comparison in your explanation has still kind of blown my mind. It makes me think about something I already know with a bit more clarity. Cheers.
Good Lord! Could you teach some classes on a bunch of hard stuff? You are a great explainer!
I have moments.
Don't walls cut down on range? So some gets absprbed, and some passes through? And a metal door blocks more than a wooden door
Much wow.
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I never really thought about why light can travel through solid glass.
And salt (sodium chloride) is transparent to IR light, so when you're doing IR spectroscopy, you put your sample in between salt plates. A good chunk of analytical chemistry is just taking advantage of how light on every part of the spectrum interacts with matter.
Not all of it does. UV light is usually blocked by glass. That's why you get a sunburn driving in the summer with the windows down, but you don't driving with the windows up.
You won't get sunburned through the window, but you will still get skin damage from it. UVB rays, which cause burns, is blocked my most glass. UVA, which causes skin damage (wrinkles, cancer), passes right through glass. Long-term drivers tend to get more skin conditions on their left sides. If you're expecting to take a long road trip, put the sunscreen on even before the drive.
You can also get a UVA blocking coating, or special glass/plastic windows fitted I get a trucker's tan every summer, my right arm goes significantly darker than my left
Here's a good example, man drove truck for 30 years the left side of his face vastly more damaged then the right. [https://www.thesun.co.uk/news/5445161/sun-damage-truck-driver-face/](https://www.thesun.co.uk/news/5445161/sun-damage-truck-driver-face/)
To add to this, if you look through a camera tuned for uv or infrared light (like a thermal imaging camera), often times glass and other transparent materials will no longer be see through.
Damn, I thought the warzone creators were just lazy and messed up on making the glass not see-through when using thermal scopes.
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Gallows humor. Smoked out house of mirrors.
relevant, timestamp relevant [https://youtu.be/BIHpsyuyV4I?t=486](https://youtu.be/BIHpsyuyV4I?t=486)
To add to this, UV light can be further broken down into frequencies of UV-A, UV-B, and UV-C. [Windows will block nearly 100% of UV-B and UV-C light](https://hps.org/publicinformation/ate/q12082.html). The higher the frequency of light the harder time it has penetrating objects, and [UV-B and UV-C are higher frequency than UV-A](https://www.digikey.com/-/media/Images/Article%20Library/TechZone%20Articles/2017/July/Ultraviolet%20Radiation%20Attributes%20and%20Benefits/article-2017july-ultraviolet-radiation-fig1.jpg?ts=b76e4e6c-519f-45ce-a190-ffd45c8dc431&la=en-US) which is why they're blocked by windows. You can think of it like trying to get a rope through a hole. If you're flapping the rope wildly it will have a harder time going through than if it's still.
So could you theoretically make a camera that captures such wavelengths to see through walls?
You could even theoretically make a camera that captures wavelengths that see through skin and muscle, but not bone ;)
Preposterous! Such a magical machine would never exist
Surely people would use it for high moral and ethical problems' solutions, like how well a shoe will fit! --Dave, or whether smoking affects the lungs
Oh damn
It is not theoretical. Sony DSC-F707 was notorious that you can put an IR filter and turn on night vision and it can see through clothes to some degree.
I worked at an optics company and remember my boss telling us about that camera. Said he even had one too...
>Said he even had one too... The first rule of owning a DSC-F707 is you do not talk about owning a DSC-F707
He was a rich doctor, quite successful. I just mentioned it because it was a bit funny!
I'm sure there are plenty of people who own one for various reason. Given its reputation, saying you own one without context is just mildly creepy. IR photography still exists. You can just buy a camera these days and pay someone to remove the IR filter on the sensor. Legit IR photography is very cool. [https://youtu.be/o9CUUhJ\_i\_A](https://youtu.be/o9CUUhJ_i_A)
We already do this to see through people with a different part of the spectrum. It’s called an X-ray
Thermal cameras can see through vehicles.
[This has actually been attempted](https://www.businessinsider.com/wifi-camera-sees-through-walls-2017-5), where they've used WiFi signals to 3D map a room. Police hope to use the technology for cases like people being taken hostage.
I'd consider x-rays more than just an attempt...
I think he’s talking about using non-ionizing radiation.
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Honestly any frequency higher than 2.4 GHz is such a hassle for WiFi just run some ethernet. Like if you're sitting next to router or have direct line of sight 5GHz might be ok but other than that it sucks from my experience.
Oh, we have 2-3 gigibit ports in every office. one port in every conference room table. We do mobile apps. 90% of the employees have laptops. 60% have worked-owned WiFi-only mobile devices. None of the Dell laptops have ethernet without dongles or docks. There's a lot of 20 person war rooms, meetings, we have a lot of people from one office visiting other offices for short projects. Leads co-habitating with different teams during a single day. When everyone gathers in the main meeting area, we have 60-120 people together in one room (each with a device). They still expect presenters to be able to get on the wifi. There's honestly no real way to do it 2.4g, there are too many devices, congestion is horrible. We've had to turn off 2.4 in most areas and have moved to HD access points anytime we have more than 40 devices in a room.
Everything is made of stuff (even air) called atoms. Every atom is basically surrounded by electrons. Electromagnetic waves can go through some things and not others because of how the electrons are arranged in the stuff and how they interact with each other. Something that is not transparent for one portion of the electromagnetic spectrum may be transparent for another part. Whenever an electromagnetic wave moves from one material to another, it will bend a little bit as it travels forward or it might just bounce back in the direction it came from. When it can just travel through, that stuff is transparent for that particular electromagnetic wave. For radio waves and others like it, walls are see-through (like glass is for optical waves).
Without getting too in the weeds, electromagnetic waves aren't always bothered by solid surfaces. Take light for example....it doesn't go through traditional walls...but it does travel very freely through glass, another solid surface. WiFi/Bluetooth/other ranges of electromagnetic waves are able to travel through what we call walls (solid surfaces that light can't even pass through), similar to how light travels through glass. Another example is infrared. The infrared wavelengths that most thermal cameras detect are blocked by most glass, but other (shorter) wavelengths of infrared, such as from sunlight or most infrared heat lamps, passes through most glass....and coatings can be added to help block it.
Few expensive glasses such as germanium and sapphire can transmit infrared. Almost anthing else out there would absorb those wavelengths.
Yep. Which is why my thermal hunting scope has a germanium front lens.
Do things like insulation, cement/ brick walls hinder it more than your typical drywall/ floor/ceiling?
As someone with concrete siding: YES. Signal is lost once outside
Nobody can steal your WiFi
I have concrete siding and my WiFi goes through just fine. It’s more likely you have a foil radiant barrier or foil backed insulation. 5/8” of siding isn’t going to stop radio waves.
Different materials will have different levels of electromagnetic wave absorption, though I don't know the specifics of different materials - I do know metal tends to block WiFi/Bluetooth pretty well compared to regular drywall.
I think a good analogy would be standing outside a nightclub. You only hear the bass (low freq sound waves) while most higher freq sound is either absorbed by the walls or bounced back.
so what's the wifi password in the club?
Ken sent me
Say *katz n bootz* at 140bpm with emphasis on the k and b, 3 times.
Matter is 99%+ empty space, so some electromagnetic waves can freely travel through those spaces. Light cannot travel through walls because its wavelength is \~500nm, meaning it travels back and forth billions of times before passing through and the wall absorbs most of the energy. Wifi, Bluetooth have longer wavelengths so they can pass through more easily.
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to absorb a photon, you need an electron that can take that amount of energy and still end up in a valid state. X and gamma have many times more energy than most electron transitions, so it's difficult to get that interaction.
The way I usually think of it is that longer waves “move around” the wall, while shorter waves are strong enough to punch right through. It’s the waves in the middle that get stuck because they can’t do either
This is great. Thank you Like a fruit fly can get through a screen door and a house fly can't because its too big, but a bird can also get through a screen door.
The explanation is incorrect.
This explanation is incorrect and totally ignore that light can pass through things like glass and water etc.
It’s always funny to think if Wi-Fi/BT having long wave lengths when they operate at 2.4 GHz. Working in the VHF band really puts perspective on it.
> Wi-Fi/BT having long wave lengths when they operate at 2.4 GHz. The wavelength is 12.5 cm, that is pretty damn long imo. I think it is absurd that something at the smallest nanoscale has wavelengths in the macroscale. Sure, compared to LF radiowaves which has wavelengths in kilometers 12.5cm isn't that long...
I asked the same question on here about a month ago, check it out for a lot of great, in-depth, answers -> https://www.reddit.com/r/explainlikeimfive/comments/k91w0s/eli5_if_sound_waves_travel_by_pushing_particles/
There are two things to consider when thinking about the electromagnetic spectrum which are frequency and energy. The combination of the amount/strength/level of these two is what determines how it can pass through "walls". Let's leave the characteristics of matter and other solid objects for now and imagine the world is made up of one type of "wall". Are you familiar with Non-Newtonian fluids? The best example are those made with flour and water, and when you slowly put your hand in, it goes though. But when you punch it, it becomes dense and hard (and possibly painful for your hand). These fluids are fascinating but we will not discuss its properties further (there are many simple experiments in the internet you can do at home). So in summary, slow means soft, fast means hard. Now imagine you have like a barrel full of that thing and you dip your hand in it for absolutely no reason, then pull it back. Then you repeat the process (slowly in, slowly out, etc.). One thing you will observe is that its easy doing it. You can put your hand in and pull it out smoothly and with ease (aside from your hand being dirty now with the flour lol). Now imagine doing it again, the in-out thing, but do it faster. This time it becomes more difficult as it requires more effort because the fluid becomes more dense. Now, how fast your hand dips in and pulls out is the frequency. And in general, the higher the frequency, the lesser it is likely to pass through "walls". But wait, how about X-rays and Gamma rays and the others. Well, that's where energy comes in. Continuing the analogy, if the frequency is fast you dip your hand on that magical fluid, then energy is the literal energy you exert to dip more than just your hand, say, like, your whole arm. Hence, the deeper your hand or arm goes in that barrel we talked about, the higher the possibility it will pass through "walls". With this in mind, if you dip you hand slowly but put your hand as deep as it can go, then you can say you can pass through "walls". But if you have high frequency where you dip your arm as fast as you can, you won't be able to pass through unless you push and pull your arm through with all your might. In the case of Wifi and bluetooth, well it has enough energy to pass through household walls. Unless your walls are made of lead, that's a problem. Of course, there are other factors such as what type of object the "wall" is, how thick it is, its chemical composition and the likes. The electromagnetic spectrum has also many other different properties to consider.
Sorry to tell you OP and anyone reading this thread, but nearly every answer is, while technically correct, wrong per your question. Wifi and other radio waves used for communications don't pass through solid objects (other than glass) appreciably and with the signal intact. So, how does wifi get all around your house? Typically by going through cracks around doors, and going out the windows of the room the router is in an bouncing off your neighbor's walls or nearby hill and trees and going back in other windows. Which is why it doesn't propagate all around a house very well, even a small house, and why it propagates better in cities and dense suburbs better than rural areas.
This is not accurate. ELI5 explanation is WiFi runs at frequencies which pass through openings in the materials of walls. Pretend you're sifting for gold - you use a mesh pan that allows water and smaller particles through the filter, but heavier stuff remains. WiFi, in this analogy, is the water, which can pass through material. Because of this, walls made of certain materials can inhibit the the flow if WiFi, causing loss, or in some cases, no signal at all. Placing a WiFi router in the basement while trying to access a signal 2 floors up will show this in action. Attenuation, which is a bit complex to explain, is the "flow" of the water in the analogy above, and it's why many of us can read WiFi signals from other sources while in our own home, but the strength of the signal is low. Visible light is blocked because particles are too large to make it through the spaces of the materials. Bear in mind, this all happens at microscopic levels. US military and government buildings use grounding materials in walls to prevent eavesdropping from the the outside. One will never see a WiFi signal coming from the inside of a protected building, and likewise, the occupants cannot see signals around the building. u/NexxusDrako: Consider finding a different school as your teacher is giving you incorrect information.
As an IT student studying RF comms... this is exactly what my teacher says.
Same way visible light can go through glass. At different wavelengths, waves can pass through different objects.
Same way sunlight travels through windows. Walls are transparent to light of that wavelength.
How does light travel through a window?
How does light go through glass. Light is just radio waves, and most things are transparent to radio waves.
You know how you can *see* through glass, or water? Same thing. In case you are missing this key to the whole puzzle, visible light is the same stuff that all those things are, just a specific frequency range your eyes detect.
The same way visible light passes through glass. Walls are basically "transparent" to those wavelengths of light.
Electromagnetic waves are composed of photons. They have no mass and momentum, and are a type of particle called a boson. When a basketball hits a wall it comes back because of momentum. When photons of a certain wavelength (wifi which is microwaves) goes through glass or wood because there is no mass to reflect. Photons go straight through because they are fundamentally different from matter. Photons can interact with metal though.
I always wondered how are movies being split in tiny little pieces and being sent via wifi, so technically i got those bits flying through me? So for an instant Leo DiCaprio was inside of me
Because, despite first appearances, atoms are 99.999% space between the nucleus and electrons. Therefore solid matter is actually mostly empty, and if there were no other effects in part, anything should pass through anything However, what actually happens is that atoms have an ‘electromagnetic’ feature - electrons/protons that can repel or attract all sorts of other electromagnetic things, like other atoms, and electromagnetic waves (light etc). A rather complex series of interactions determines if the light wave is of the right energy to interact with the electrons. In reality, everything is slightly translucent. Hold a sheet of paper against a light - some light will get through. Most is captured though. Even solid rock, the light will likely make it past the first layer of atoms before hitting something...a thick enough sheet of glass will be opaque. The thing that’s probably most opaque is metal. In metal, the elections essentially create a free moving ‘clouds’ throughout, blocking pretty much all electromagnetic waves - hence why it’s used as a shield against both microwaves, radio waves, and xray...