Can a spaceman survive length contraction?

[Kyrisch]

After two pages of repetition, the point is still not getting across...

 

The measured distortion is only measured in other reference frames. You are at rest in your own reference frame, and therefore do not undergo any length contraction. This is evidenced by the fact that you are traveling at 99% the speed of light relative to any countless arbitrary frames of reference, and you are experiencing no contraction as measured in your own frame.

[NowThatWeKnow]

...This is evidenced by the fact that you are traveling at 99% the speed of light relative to any countless arbitrary frames of reference,...

 

This is mentioned a few times in this thread but afaik the only frames moving at relativistic speeds relative to Earth are because of the expansion of space and not motion. This brings us back to my question in the last paragraph in post 23. Unless we can say for sure that speed from space expansion causes time dilatation and length contraction and not just motion through space, should we use it as an example to prove a point?

 

Last plug for my cause. I will start a new thread if it isn't resolved.

[Sisyphus]

I started a thread once called "Is relativistic mass an illusion" and got varied responses. What you observe from different frames will vary but no matter what frame your are in, 1' is 1' and you can not mix frames as you are suggesting above. I do agree the mirror may not have been the best analogy.

 

Please follow the link. http://en.wikipedia.org/wiki/Ladder_paradox I'm not mixing reference frames. 1' is 1' for you, but your 1' is not my 1'.

 

This is mentioned a few times in this thread but afaik the only frames moving at relativistic speeds relative to Earth are because of the expansion of space and not motion.

 

No. You seem to be confusing reference frames with actual objects. They're not. They're just metrics. You can pick any reference frame you want. It's arbitrary. Whether there is anything at rest in it doesn't matter in the slightest. So yes, there are an infinite number of reference frames in which the Earth is moving at >0.999999999999999C. They just tend not to be very convenient.

 

But it may interest you that there are, in fact, plenty of particles moving at more than half C relative to the Earth that collide with the Earth all the time. In fact, these allowed us to have some of the first direct observations of relativistic time compression.

[swansont]

But it may interest you that there are, in fact, plenty of particles moving at more than half C relative to the Earth that collide with the Earth all the time. In fact, these allowed us to have some of the first direct observations of relativistic time compression.

 

And we put many particles into such a reference frame with particle accelerators.

 

——

 

The ladder is a good "paradox" to study because it shows how simultaneity is not absolute.

[asprung]

Some say that the spaceman will actually undergo length contraction and distortion. Some say that such length contraction and distortion will only appear in different reference planes. Is the fact that clock slowing has been measured as actually occurring some indication that what happens to the spaceman is real and that he should feel it. If the clock slowing will affect his ageing why should not the length contraction affect him physically?

Edited May 9, 2009 by asprung

[Mr Skeptic]

Is the fact that clock slowing has been measured as actually occurring some indication that what happens to the spaceman is real and that he should feel it.

 

The clock slowing is real and he will not feel it. You keep forgetting about the other side of relativity, the reference frame that he is moving with respect to. If person A and person B are moving relative to each other, they will both say the other guy's clock is running slow and that he is distorted.

 

Remember, no one is ever "moving". Movement is always relative to something else.

[NowThatWeKnow]

Please follow the link. http://en.wikipedia.org/wiki/Ladder_paradox I'm not mixing reference frames. 1' is 1' for you, but your 1' is not my 1'.

 

...the Earth is moving at >0.999999999999999C. They just tend not to be very convenient...

 

But it may interest you that there are, in fact, plenty of particles moving at more than half C relative to the Earth that collide with the Earth all the time. In fact, these allowed us to have some of the first direct observations of relativistic time compression.

 

Sysyphus and swansont,

The ladder paradox is interesting, I will try to think of a way my "master clocks" can simplify it. It seems I was confusing comparing different frames to mixing different frames. Sometimes I am not sure where to put that line.

 

I wasn't thinking of minute particles everywhere traveling a high speeds relative to us and of course the particle accelerators where we can observe the results of relativistic speeds.

 

This has been an educational thread for me and your tolerance to physics ignorance is admirable. Thank you.

 

Now, on to the next problem. Does the separation of matter caused by the expansion of space and the movement through space relative to us, such as a rocket, both experience the same time dilation and length contraction from Earth's point of view?

Edited May 9, 2009 by NowThatWeKnow

[asprung]

Does not the spaceman experence his clock slowing by his slower ageing?

[Kyrisch]

Does not the spaceman experence his clock slowing by his slower ageing?

 

Either you are trolling or you're simply incredibly thick. Relativistic effects are not experienced in your own reference frame because you are at rest with respect to everything else. An observer will see the 'spaceman's' clock slow, while the spaceman will see the observer's clock slow. Neither one experiences length contraction or time dilation in their own frames.

[asprung]

Then why should the spaceman age slower?

[Klaynos]

Then why should the spaceman age slower?

 

Relative to what?

[asprung]

Than he was when he started the trip. Slower ageing - cell division etc. is as much as a physical effect as organ distortion.

[iNow]

He is only aging slower relative to the people who were at the location where he started. You keep missing that key term, "relative to." Relative to his own reference frame, there is no difference. He, and all the cells and organs in his body, are experiencing life just as they would back where they started.

[swansont]

Then why should the spaceman age slower?

 

You've had the benefits of dozens of posts explaining relativity to you. Perhaps you should reread some of them.

[asprung]

The spaceman who leaves earth and travels at a speed approaching C ages slower than he was ageing on earth. Thus the velocity is having a physical effect on him. Yet I am told that since he can consider himself to be at rest relative other time frames he would not experience the change. This is what I understand I have been told, and being “thick” I will not comment further.

[iNow]

The spaceman who leaves earth and travels at a speed approaching C ages slower than he was ageing on earth. Thus the velocity is having a physical effect on him.

This is a false assumption. As has been pointed out to you umpteen times... He is only aging slower relative to those still back on earth. Relative to himself, there is no slowness... no difference... from his perspective, it's as if he were still standing on earth.

 

It is only relative to those back on earth that he is aging slower. Relative to himself and his own reference frame there is no difference, and hence no physical effect.

 

 

Yet I am told that since he can consider himself to be at rest relative other time frames he would not experience the change. This is what I understand I have been told, and being “thick” I will not comment further.

 

It's nothing personal, asprung, but it's somewhat frustrating. Over your 130 posts here, this issue of relativity, and how reference frames matter... How these effects are all relative to something... keeps being missed. In nearly every post you make, people respond and the concept of relative to is raised, yet despite that you still seem to ignore those corrections.

 

Your time is not the same as my time, especially when we are traveling at different velocities.

Your meter is not the same as my meter, especially when we are traveling at different velocities.

 

If you state anything about length, or if you state anything about time, then you MUST do so relative to some external frame of reference. It's that simple. There is no such thing as absolute time, there is no such thing as absolute length, and the concept of nowness is a tautology that has no practical utility outside of metaphysics. If this were a metaphysics forum, the responses you receive would likely be more appealing to you. However, since you continue to post in the relativity forum, you will continue to receive explanations in terms of relativity... a theory which has been tested countless times for over a century and which has never once faultered in any of the countless challenge thrown its way.

[asprung]

I am really confused. As the spaceman leaves earth he is ageing at a certain rate which decreases with velocity increase. This would seem to be an effect he experences in his own frame.

[iNow]

I am really confused. As the spaceman leaves earth he is ageing at a certain rate which decreases with velocity increase. This would seem to be an effect he experences in his own frame.

 

The decrease in aging rate you reference is relative to earth, compared to which his velocity is significantly higher.

Relative to his own frame, there is no difference, and he experiences the aging process just as he would anywhere else.

 

In his own reference frame, there is NO change in the rate which he is aging.

[Mr Skeptic]

I am really confused. As the spaceman leaves earth he is ageing at a certain rate which decreases with velocity increase. This would seem to be an effect he experences in his own frame.

 

But does his velocity increase? If his velocity is not zero, then you are not looking at him from his own frame of reference.

[asprung]

The decrease is a decrease in his own rate. He grows older slower with increasing velocity.

Edited May 10, 2009 by asprung

[Mr Skeptic]

What velocity? If you ask him, he's not moving.

[iNow]

The decrease is a decrease in his own rate. He grows older slower with increasing veloicty.

 

Relative to whom/what?

[Kyrisch]

The spaceman who leaves earth and travels at a speed approaching C ages slower than he was ageing on earth. Thus the velocity is having a physical effect on him. Yet I am told that since he can consider himself to be at rest relative other time frames he would not experience the change. This is what I understand I have been told, and being “thick” I will not comment further.

 

Ahah! I think I understand where your confusion is coming from.

 

A spaceman who leaves earth traveling at near light-speed will age slower relative to observers at rest on Earth, but the man himself will not experience any slowing of time in his own frame. He will, however, notice that his trip will take less time than it should, due to the length contraction caused by the apparent near light-speed velocity. The physical length of his trip will contract, and it therefore will take less time to complete it. As such, when he comes back, he will have aged less than he 'should have' because the trip was shorter than it 'should have' been. When he returns to earth, the observers at rest will tell him that he was gone the proper amount of time, as no length contraction was observed by them, resulting in the apparent age difference.

[swansont]

A

A spaceman who leaves earth traveling at near light-speed will age slower relative to observers at rest on Earth, but the man himself will not experience any slowing of time in his own frame. He will, however, notice that his trip will take less time than it should, due to the length contraction caused by the apparent near light-speed velocity. The physical length of his trip will contract, and it therefore will take less time to complete it. As such, when he comes back, he will have aged less than he 'should have' because the trip was shorter than it 'should have' been. When he returns to earth, the observers at rest will tell him that he was gone the proper amount of time, as no length contraction was observed by them, resulting in the apparent age difference.

 

It is important to note that the length contraction seen by the astronaut is observed only by him, in his frame. Observers in other frames will measure different contractions. Observers at rest on earth see no contraction.

 

Length and time are not absolutes. It depends on what frame you are in when you make the measurement.

[asprung]

I apologize for trouble I may have caused. I fully understand that according to SR, when viewed from earths frame, the spaceman will be velocity compressed (and possible injured) but in his own frame everything will be normal. What I can’t comprehend is how the single body of the spaceman can be both compressed and not compressed. Do we just have to have faith in SR or does someone have an explanation?