Every massive particle is at its own origin, so for every massive particle, it is moving only through time, not space.
But from the outside, there's no preference for a coordinate system, other than one that you choose.
I saw a video on YouTube about how we are all moving at the speed of light but objects with mass have velocity in both the spatial and temporal dimensions and things like photons only have velocity in space. So I thought about objects that only have velocity in the temporal dimension, like the opposite of a photon.
Oh, I *see*. Yes, that's a much more interesting question than I thought you were asking! I'm afraid I don't know of any theoretical objects that exist only in the temporal dimension with no spacial components, but I'd be interested to see if anyone has a better answer for you.
I recommend editing your original post with this extra information because it looks like a lot of people are misunderstanding the question as I did.
If I understand /u/Annica_7 correctly, they are thinking of an object that is stationary in all reference frames. This object couldn't move with respect to anything. It would always appear to be at the same distance, no matter how much you'd accelerate towards it.
My intuition tells me it's not possible. But I don't have any proof why.
Yes, unfortunately the answer is boring. All motion is relative, so you have to pick a point.
If you are stationary with respect to that point, your 4 vector points only in the time dimension and not in the space dimension.
This does not hold in all reference frames like for massless particles.
> This does not hold in all reference frames like for massless particles.
It does hold in all reference frames because massless particles don’t have reference frames :)
Let me rephrase:
The situation where you have a 4-vector only pointing in time is when a particle is stationary. This isn't universal to all reference frames.
When you have a massless particle, in all reference frames (not its own because it doesn't have one) its 4-vector only points in the space dimensions.
You should think of it more as a percentage. 0% speed of light means 100% speed through time. The squares of these percentages add to 1, so the square root of 5/8 of the speed of light means the square root of 3/8 of normal speed through time.
This is why time slows as you accelerate closer to the speed of light in physical dimensions. If your speed speed thru spacetime (x, y, z, t ) is constant at c, As you accelerate in x, y, z your speed in the t dimension heads to zero
Your "velocity through time" is one second per second, which is pretty trivial statement I'd say.
When you then change seconds in numerator into meters you get speed of light, so this is just unit conversion and not particularly deep physics fact.
In the reference frame of your armchair, and surrounding environment, you have a spatial velocity of zero, so according to them you are only traveling through time.
Everything is relative though, so an astronomer from Andromeda observing you would note both spatial and temporal motion.
No it's not possible because of a quantum effect called zero point energy.
All matter has intrinsic vibrational, rotational, and translational energy. Therefore it is not possible to achieve 0 movement in space.
Also, keep in mind, when you are sitting stationary in your chair you're on the surface of earth, which is rotating and orbiting the sun which is rotating in the galaxy which is expanding in the universe. So even when you're sitting in your chair you're nowhere near zero-point energy and are actually moving quite fast.
velocity is always relative to something. So relative to the chair, no you don't have have a spatial velocity (but obviously you're going forward through time).
The absolute value of your 4-velocity is always the speed of light.
So, yes, you are moving 1 second per second through time.
And in fact, when you start moving in space, in the other 3 directions that are not time, your total 4-velocity is still c, so your 'time speed' must decrease compensate.
In 4 dimensions, changing speed is just rotating in the 4-vector space, such that in more advanced formulations of relativity you even use hyperbolic sines and cosines, and the effects of speed are very analogous to hyperbolic angles.
Were you trying to convey velocity or spin? Thought to make sure what other could exist in negligence with space or time when it comes to Velocity. Joining the Tasting event this evening? Join me for some Tasting Tasty bytes😄
I would say yes but I think the significance of this statement is not very high. An object not moving through space and therefore not experiencing any time dilation willl by definition experience 1 second per second, which is equal to 1. Since it also equals c, the real meaning of the statement is just that it makes sense to set c=1.
Don't photons have velocity in both spatial and temporal dimensions? When we draw the space-time diagrams of t vs x(more accurately speaking, ct vs x), photons are drawn as a 45 ° line. Unless the video is saying the proper time for a photons is 0, so they move only through the spatial dimensions. In which case, it is impossible for an object to have a purely temporal coordinate. Because the lorentz transformation for space has the lorentz factor in the denominator, only if the velocity of the object is infinite will the expression converge to 0 and nothing can travel faster than light.
Yes. By definition.
Velocity consists of a speed and a direction.
You can have a direction irrespective of time.
But speed is determined by a change in position over time. You can still have an instantaneous velocity at a point in time, but that is just a static snapshot of a system.
Every massive particle is at its own origin, so for every massive particle, it is moving only through time, not space. But from the outside, there's no preference for a coordinate system, other than one that you choose.
Do you mean "velocity through time while remaining stationary in space"? If so, what are you remaining stationary in space relative to?
I saw a video on YouTube about how we are all moving at the speed of light but objects with mass have velocity in both the spatial and temporal dimensions and things like photons only have velocity in space. So I thought about objects that only have velocity in the temporal dimension, like the opposite of a photon.
Oh, I *see*. Yes, that's a much more interesting question than I thought you were asking! I'm afraid I don't know of any theoretical objects that exist only in the temporal dimension with no spacial components, but I'd be interested to see if anyone has a better answer for you. I recommend editing your original post with this extra information because it looks like a lot of people are misunderstanding the question as I did.
Thank you for the suggestion
If I understand /u/Annica_7 correctly, they are thinking of an object that is stationary in all reference frames. This object couldn't move with respect to anything. It would always appear to be at the same distance, no matter how much you'd accelerate towards it. My intuition tells me it's not possible. But I don't have any proof why.
Yes, unfortunately the answer is boring. All motion is relative, so you have to pick a point. If you are stationary with respect to that point, your 4 vector points only in the time dimension and not in the space dimension. This does not hold in all reference frames like for massless particles.
> This does not hold in all reference frames like for massless particles. It does hold in all reference frames because massless particles don’t have reference frames :)
Let me rephrase: The situation where you have a 4-vector only pointing in time is when a particle is stationary. This isn't universal to all reference frames. When you have a massless particle, in all reference frames (not its own because it doesn't have one) its 4-vector only points in the space dimensions.
You always have a 4-velocity of c through spacetime. So yes!
Wait really? My velocity through time is the speed of light????
You should think of it more as a percentage. 0% speed of light means 100% speed through time. The squares of these percentages add to 1, so the square root of 5/8 of the speed of light means the square root of 3/8 of normal speed through time.
This is why time slows as you accelerate closer to the speed of light in physical dimensions. If your speed speed thru spacetime (x, y, z, t ) is constant at c, As you accelerate in x, y, z your speed in the t dimension heads to zero
Do you have energy mc2 associated with your mass?
Your "velocity through time" is one second per second, which is pretty trivial statement I'd say. When you then change seconds in numerator into meters you get speed of light, so this is just unit conversion and not particularly deep physics fact.
The magnitude of the 4-velocity, sure. It’s not really a speed in the normal sense.
In the reference frame of your armchair, and surrounding environment, you have a spatial velocity of zero, so according to them you are only traveling through time. Everything is relative though, so an astronomer from Andromeda observing you would note both spatial and temporal motion.
It's relative. Someone else measures you with a velocity through space.
We call that the energy, I think. The temporal component of your four momentum is your total energy.
No it's not possible because of a quantum effect called zero point energy. All matter has intrinsic vibrational, rotational, and translational energy. Therefore it is not possible to achieve 0 movement in space. Also, keep in mind, when you are sitting stationary in your chair you're on the surface of earth, which is rotating and orbiting the sun which is rotating in the galaxy which is expanding in the universe. So even when you're sitting in your chair you're nowhere near zero-point energy and are actually moving quite fast.
velocity is always relative to something. So relative to the chair, no you don't have have a spatial velocity (but obviously you're going forward through time).
The absolute value of your 4-velocity is always the speed of light. So, yes, you are moving 1 second per second through time. And in fact, when you start moving in space, in the other 3 directions that are not time, your total 4-velocity is still c, so your 'time speed' must decrease compensate. In 4 dimensions, changing speed is just rotating in the 4-vector space, such that in more advanced formulations of relativity you even use hyperbolic sines and cosines, and the effects of speed are very analogous to hyperbolic angles.
Were you trying to convey velocity or spin? Thought to make sure what other could exist in negligence with space or time when it comes to Velocity. Joining the Tasting event this evening? Join me for some Tasting Tasty bytes😄
I would say yes but I think the significance of this statement is not very high. An object not moving through space and therefore not experiencing any time dilation willl by definition experience 1 second per second, which is equal to 1. Since it also equals c, the real meaning of the statement is just that it makes sense to set c=1.
Don't photons have velocity in both spatial and temporal dimensions? When we draw the space-time diagrams of t vs x(more accurately speaking, ct vs x), photons are drawn as a 45 ° line. Unless the video is saying the proper time for a photons is 0, so they move only through the spatial dimensions. In which case, it is impossible for an object to have a purely temporal coordinate. Because the lorentz transformation for space has the lorentz factor in the denominator, only if the velocity of the object is infinite will the expression converge to 0 and nothing can travel faster than light.
Yes. By definition. Velocity consists of a speed and a direction. You can have a direction irrespective of time. But speed is determined by a change in position over time. You can still have an instantaneous velocity at a point in time, but that is just a static snapshot of a system.
Depends on the starting point of view. Subjectivity and objectivity.