Special relativity thought: Traveling to the future relative to a particle

[L Drago]

TL;DR Summary

The ether drift was proved wrong by Michelson-Morley experiment. Earlier it was believed that it would slow down by a factor of (1-v²/c²)^(1/2). Now we know ether is wrong. The six atomic clocks in different regions show by same time delay and does not indicate ether drift till date.

I think that we travel to future all the time. As all intertial frame of motion is relative. We are currently travelling at very high speeds with relative to a particle accelerator's particle and time is slowing down for us with relative to the particle. I think so we are also travelling to future also with respect to that particle. We are travelling at multiple speeds at the same time although we are at rest.

 

[Mister T]

I think that we travel to future all the time.

No. We don't travel from one clock-reading to another. We travel from one location to another, and if we know the distance between the locations, and the time it takes to get from one location to the other, we can calculate our speed. Speed has units of distance divided by units of time. Traveling through time is nonsense, it just means that clock-readings always advance, so that if we read a clock now, and then read it again later, the latter reading will be greater than the former reading. That's not traveling, that's just the passage of time.

We are travelling at multiple speeds at the same time although we are at rest.

No. Being at rest just means the speed is stable at zero. The speed of a person is not a property of that person. It's just a measure of the distance he travels divided by the time he spent traveling. The speed of the person measured in different reference frames may be different, but that's not because of anything the person is doing differently in the different reference frames, it's simply because the reference frames are in motion relative to each other.

 

[L Drago]

No. We don't travel from one clock-reading to another. We travel from one location to another, and if we know the distance between the locations, and the time it takes to get from one location to the other, we can calculate our speed. Speed has units of distance divided by units of time. Traveling through time is nonsense, it just means that clock-readings always advance, so that if we read a clock now, and then read it again later, the latter reading will be greater than the former reading. That's not traveling, that's just the passage of time.

No. Being at rest just means the speed is stable at zero. The speed of a person is not a property of that person. It's just a measure of the distance he travels divided by the time he spent traveling. The speed of the person measured in different reference frames may be different, but that's not because of anything the person is doing differently in the different reference frames, it's simply because the reference frames are in motion relative to each other.

But in different frame of references though we are at rest we travel in multiple speeds.

 

[Ibix]

But in different references though we are at rest we travel in multiple speeds.

The point is that "travelling at speed $v$" is an incomplete sentence. The complete version is "travelling at speed $v$ relative to object X". You can substitute "frame" for "object" if you like. Everything has a single well-defined speed relative to any specified frame or object.

In everyday life, we typically leave out the reference object and say things like "you must not drive faster than 30mph". In that case, we mean "...relative to the surface of the Earth". We can get away with being sloppy in that context because it's widely understood what we mean. We cannot get away with it in relativity, though, because we typically discuss circumstances floating in space, or we are explicitly considering measurements made relative to different objects.

So "[w]e are travelling at multiple speeds at the same time although we are at rest" is missing the point entirely. We have a single well-defined speed with reference to any chosen object or frame, but we can pick many different frames to describe it.

 

[jbriggs444]

I think that we travel to future all the time. As all intertial frame of motion is relative. We are currently travelling at very high speeds with relative to a particle accelerator's particle and time is slowing down for us with relative to the particle. I think so we are also travelling to future also with respect to that particle. We are travelling at multiple speeds at the same time although we are at rest.

You have made a number of posts along these lines, making statements in isolation. Giving no indication that you have understood any of them. And then asking whether you have understood correctly.

It seems that you need to learn about coordinate systems and frames of reference.

I like to think about coordinate systems by pretending that we have a transparent plastic sheet that we have placed over a table. There are grid lines on the sheet (for a cartesian coordinate system). We can identify any point on the table by the pair of grid lines that intersect at that point. Those are the coordinates of the point.

If we change out plastic sheets, we have not affected the table. But the points on the table all have new coordinates.

If a point is moving, we can record its motion as a series of coordinate values and calculate how rapidly those coordinates are changing.

If a plastic sheet is moving, we can still record the motion of a point as a series of coordinate values and calculate how rapidly the coordinates are changing.

The same point will have different speeds depending on how fast we drag a plastic sheet over it.

 

[Dale]

I think that we travel to future all the time. As all intertial frame of motion is relative. We are currently travelling at very high speeds with relative to a particle accelerator's particle and time is slowing down for us with relative to the particle.

Yes. I agree.

But in different frame of references though we are at rest we travel in multiple speeds.

This is poorly worded. This would be better: “in different frames of reference we travel at different speeds, though we are at rest in one frame”.

If we are inertial then there is no frame in which we travel at multiple speeds. We travel at different speeds in different frames, but not multiple speeds in any one frame.

 

[L Drago]

Yes. I agree.

This is poorly worded. This would be better: “in different frames of reference we travel at different speeds, though we are at rest in one frame”.

If we are inertial then there is no frame in which we travel at multiple speeds. We travel at different speeds in different frames, but not multiple speeds in any one frame.

Thanks a lot for correcting me

 

[Mister T]

But in different frame of references though we are at rest we travel in multiple speeds.

In each frame of reference our speed is different. But in only one of those frames our speed is zero. There is no reason to give any special preference to the one in which we're at rest. You seem to do that when you say "though we are at rest" You could just as easily replace it with the phrase "though we have a speed of 12.82 m/s".

 

[Ibix]

A mathematical analogy. Imagine four people sitting around a square table and an ant walking across the table at 1mm/s relative to the table. One person sees the ant moving left-to-right and says the ant has velocity $(+1,0)$. The person opposite them says the ant is moving right-to-left so it has velocity $(-1,0)$. The people sitting between them say the ant has velocity $(0,+1)$ and $(0,-1)$. Does the ant really have four different velocities?

No it does not. It has one velocity - it is doing what it is doing in reality. If we're hoping to describe that reality there had better be only one velocity in our models.

What we do have is four different representations of that velocity, because our four people are using four different coordinate systems whose x and y directions are rotated with respect to one another. This means that "the ant has velocity $(v_x,v_y)$" is meaningless unless you also specify which directions you are considering to be "increasing x while leaving y constant" and "increasing y while leaving x constant".

Note that in all these cases the ant has the same speed, just in different directions. That is because, while the reference frames do not share a notion of x and y directions, they do share a notion of what "at rest" means - it means at rest with respect to the table. Once you add in the possibility of frames which do not consider the table to be at rest, the speed will not be equal in all representations either.

 

[Dale]

No it does not. It has one velocity - it is doing what it is doing in reality.

It is important to point out, in support of this statement, that there is a definition of velocity that is frame-invariant. It does not depend on the reference frame chosen. Strictly speaking, it is the components of that velocity that are coordinate-dependent. But the velocity itself is a geometric quantity that exists independent of any coordinate chart.