Is Relativity Reality?

[Twiglet]

The basic tenet of SR is that all frames of reference are equally valid.

Just minutes ago Twiglet, you said that that was a philosophical question, not a scientific one.
.

Stop goading mistermack.

The distinction is basic. Relativity makes assumptions.

You asked if I could say whether they are always true, which of course, I can't. I can only state they are consistent with experimental results. I framed your original question in a way that would help anyone solving it using relativity to understand how relativity works, in the process of obtaining the answer.

Are you just too lazy to even give it a go? Do you prefer to piddle about with the linguistic distinction between truth and science, or do you want to understand the science? Probably a good idea to understand the science if you want to criticise it, IMO.

[mistermack]

Twiglet, maybe a little goad there, but true.
Anyway, it's the crux of what I'm asking really. You said ''The basic tenet of SR is that all frames of reference are equally valid''. Now I understood that that was the basic tenet of Galilean and Newtonian relativity, and that SR was different in that it was somewhat restricted by the fact of the real-life limit of c.

That's why I would really really really like an answer to my question, for a single particle in otherwise empty space, are the valid reference frames limited to moving at less than the speed of light relative to it?
ie, my little 'sphere diagram' with possible vectors of 300,000 kps in any direction. Is it valid, or not?
Or to put it another way, can a Lorenz transformation be done from one stationary frame, to another travelling away from it at 350,000 kps?
.

[Twiglet]

Twiglet, maybe a little goad there, but true.
Anyway, it's the crux of what I'm asking really. You said ''The basic tenet of SR is that all frames of reference are equally valid''. Now I understood that that was the basic tenet of Galilean and Newtonian relativity, and that SR was different in that it was somewhat restricted by the fact of the real-life limit of c.

That's why I would really really really like an answer to my question, for a single particle in otherwise empty space, are the valid reference frames limited to moving at less than the speed of light relative to it?
ie, my little 'sphere diagram' with possible vectors of 300,000 kps in any direction. Is it valid, or not?
Or to put it another way, can a Lorenz transformation be done from one stationary frame, to another travelling away from it at 350,000 kps?
.

A situation where a particle exceeds the speed of light is simply unphysical, because it would need infinite energy to get there. In the laboratory of the real world, no particle has ever been observed moving faster than c.

You really should have a crack at the question I asked, it will help you to understand what I think you are trying to grasp. If you examine the answer the question above, you will find that the speeds are not additive. Particle A perceives particle B to be travelling at less than c, and in fact this will always be the case unless either particle A OR particle B OR Both particles are travelling at c (in which case they would be photons). In all 3 of those cases, the observed speed from A or B would be....c

I know this is kind of freaky, the more you get into asking questions, the more freaky it seems (compared to e=mc^2, which everyone is comfy with heh). I can't answer for it's oddness, only that it seems to describe reality.

[ChildInAZoo]

Or to put it another way, can a Lorenz transformation be done from one stationary frame, to another travelling away from it at 350,000 kps?

In SR, there is no frame travelling away at 350,000 kps, or at least not one that represents a particle moving relative to the original frame. This is a fact of SR, so I can't really give any argument for it. If you don't know this already, then you do not know SR and you aren't prepared for a real argument. Your argument talks again and again of different reference frames. It does this every time you say that someone should consider a particle moving relative to a particle you have already described as moving. That you do not realize this is one of your problems.

[mistermack]

A simple yes or no would do.

[Twiglet]

A simple yes or no would do.

You can put numbers into the equation. When you do then you obtain a negative length and time going backwards
If you try to calculate the energy required to accelerate matter to the speed of light, the answer is infinite at v=c.

That is why your question doesn't apply to a real problem, as experimentally, within relativity, particles neither possess infinite energy or go backwards in time (well, actually, technically they sort of can, but not for very long, and the effect is not in relativity but I digress).

[Farsight]

Farsight and Mistermack:

Please answer the following basic question using special relativity.

Two objects, each one metre long, are moving away from each other with a speed of 2.7x10^8m/s

How long does object B appear as observed from object A?

That's .9c, so using applying the Lorentz factor √(1-v²/c²) and natural units where c=1:

length = √(1-.9²/1²)

length = √(1-.81)

length = √(.19)

length = .435 metres

Next, assume Object A is at rest, and object B is moving away from it at 2.7x10^8m/s
Object B carries a clock and waits for 1 second to elapse.
How long has elapsed on Object As clock.

Assume c=3x10^8m/s
Please show working.

Thankyou.

I presume you're asking what B would observe if he could see A's clock, and that you aware that the situation is symmetrical. The working is as above, but we're dealing with time dilation rather than length contraction, so take a reciprocal. The answer is 1/.435 seconds or:

2.3 seconds.

Note that arithmetical exercises doesn't get to the bottom of why we observe length contractiobn and time dilation, or indeed why c is the limit. For this you have to understand the underlying Pythagoras' Theorem and E=mc². And to understand the latter you have to understand the terms. You have to understand E, m, and c, which means you have to understand energy mass and time. Only then do you fully understand special relativity.

Edit:

The distinction is basic. Relativity makes assumptions.

Only then do you get past the assumptions and get to the bottom of it. Then you appreciate that mistermack, in a roundabout way, is right.

[ChildInAZoo]

A simple yes or no would do.

Sure, if you we not interested in anything about SR.

[Twiglet]

Farsight and Mistermack:

Please answer the following basic question using special relativity.

Two objects, each one metre long, are moving away from each other with a speed of 2.7x10^8m/s

How long does object B appear as observed from object A?

That's .9c, so using applying the Lorentz factor √(1-v²/c²) and natural units where c=1:

length = √(1-.9²/1²)

length = √(1-.81)

length = √(.19)

length = .435 metres

Next, assume Object A is at rest, and object B is moving away from it at 2.7x10^8m/s
Object B carries a clock and waits for 1 second to elapse.
How long has elapsed on Object As clock.

Assume c=3x10^8m/s
Please show working.

Thankyou.

I presume you're asking what B would observe if he could see A's clock, and that you aware that the situation is symmetrical. The working is as above, but we're dealing with time dilation rather than length contraction, so take a reciprocal. The answer is 1/.435 seconds or:

2.3 seconds.

Note that arithmetical exercises doesn't get to the bottom of why we observe length contractiobn and time dilation, or indeed why c is the limit. For this you have to understand the underlying Pythagoras' Theorem and E=mc². And to understand the latter you have to understand the terms. You have to understand E, m, and c, which means you have to understand energy mass and time. Only then do you fully understand special relativity.

Edit:

The distinction is basic. Relativity makes assumptions.

Only then do you get past the assumptions and get to the bottom of it. Then you appreciate that mistermack, in a roundabout way, is right.

Alright farsight, you obtained the correct numerical answers.

How about supplying the less trivial solution which speaks to the heart of mistermacks conceptual query.

Consider and observer at rest. A particle moves in direction x at 2.7x10^8 m/s. The other moves in direction -x at 2.7x10^8m/s. Taking the frame of reference of either particle, calculate the speed of the other.

That is a less trivial problem. It requires no trigonometry to calculate the answer.

[mistermack]

You can put numbers into the equation. When you do then you obtain a negative length and time going backwards
If you try to calculate the energy required to accelerate matter to the speed of light, the answer is infinite at v=c.

Jeez, it's like pulling teeth from a statue. However, I believe enmeshed in there somewhere is some kind of affirmative.
So the range of valid frames IS reduced from infinity to a finite range by the limit of c. So my ''little sphere'' of valid frames is correct in the case of a single particle.
I have a feeling Einstein would have just given me a straight yes.
.

[ChildInAZoo]

You can put numbers into the equation. When you do then you obtain a negative length and time going backwards
If you try to calculate the energy required to accelerate matter to the speed of light, the answer is infinite at v=c.

Jeez, it's like pulling teeth from a statue. However, I believe enmeshed in there somewhere is some kind of affirmative.
So the range of valid frames IS reduced from infinity to a finite range by the limit of c. So my ''little sphere'' of valid frames is correct in the case of a single particle.
I have a feeling Einstein would have just given me a straight yes.
.

Why don't you read what Einstein actually wrote about special relativity and find out?

If you do, you will find that we can use an infinite amount of reference frames to describe pretty much any situation, as long as the frames are moving in uniform translatory motion to each other. (The only exceptions are those cases where there is a significant amount of gravity involved.) Once you have a legitimate description in one frame, one can translate into any frame and one will discover that there is nothing in that frame moving at a speed greater than c.

[mistermack]

Blimey childinazoo, you've managed to completely miss the point, in spite of me practically spelling it out letter by letter. Or are you pulling my leg?
At least Twiglet got the point, even if it was painful trying to get a grudging concession that there is NOT an infinite choice of frames in a world limited by c.
.

[ChildInAZoo]

Blimey childinazoo, you've managed to completely miss the point, in spite of me practically spelling it out letter by letter. Or are you pulling my leg?

Maybe you should restate your point. Regardless, your argument hasn't anything to do with the actual theory with the proper name "Special Relativity".

At least Twiglet got the point, even if it was painful trying to get a grudging concession that there is NOT an infinite choice of frames in a world limited by c.

That's not what he said. At no point did he limit the available frames to a finite number. Again, you find this hard to understand because you decided to criticize SR before you bothered to learn SR.

[mistermack]

Maybe you should restate your point.

I honestly couldn't make it any clearer. It's there, in the simplest language I can muster. I claimed that the RANGE of valid frames is reduced from infinity by the real-life limit of c. Nobody is talking about the NUMBER of valid frames at this point, just the RANGE.
Is it or is it not valid to choose a frame such that a particle would be moving at over c?

That's not what he said. At no point did he limit the available frames to a finite number.

Finite RANGE!! I suggested attempting a Lorenz transformation for a frame receding at over c, 350,000 kps. Twiglet commented ''You can put numbers into the equation. When you do then you obtain a negative length and time going backwards
If you try to calculate the energy required to accelerate matter to the speed of light, the answer is infinite at v=c.''
I take that to mean that that frame is invalid. I'm sure twiglet will correct me if he mean't something else.
Anyway, as far as I can see, I'm only asking people to state the bleedin obvious.
(or refute it)
.

[mistermack]

Just to prove that I have the patience of a saint, here we go again.
The Universe consists of one single particle in otherwise empty space.
The diagram below shows what I think is the maximum range of valid reference frames in the blue shaded volume of the sphere. Is that right, or can you choose a frame who's velocity relative to the particle is greater than 300,000 kps? ie, that falls outside the blue volume?