# Yet another Relativity Buster Question

Discussion in 'Physics & Math' started by Singularity, Feb 20, 2006.

1. ### RosnetPhilomorpherRegistered Senior Member

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681
Who said anything about the laser being behind the rocket? Only A1 and B1 move backwards. The laser goes forward at the speed of light in the rockets frame and in any other frame moving in the same direction as the rocket.

3. ### RosnetPhilomorpherRegistered Senior Member

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681
Why go to all that trouble? Everyone here knows that Einstein himself was of the same view aboutthe matter. The difference is that he knew that <I>it does not matter in any damn way!</I>

5. ### ZephyrHumans are ONERegistered Senior Member

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3,371
But doesn't the usual relativistic velocity formula give (.9999c - v)/(1 - .9999v/c), not .9999c - v?

7. ### DaleSpamTANSTAAFLRegistered Senior Member

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I figured out one way to do it. I know you are probably all tired of seeing this graphic (http://img277.imageshack.us/my.php?image=lorentz5jj.png) but please notice there is a line in spacetime where t=t'. For example, at x=2/3 and t=2 we also have t'=2 (and x'=-2/3). If clocks undergo an impulse acceleration (a delta function) from the unprimed to the primed frame along this line then they will be synchronized. So then the procedure would be like this:

Let's say that we have two clocks in the unprimed frame, e.g. at x=0 and x=2/3. Then, to transfer to the primed frame and be synchronized after the transfer the x=0 clock needs to accelerate at t=t'=0 and the x=2/3 clock needs to accelerate at t=t'=2.

The general formula for this can be solved by using the Lorentz equations:
t'=γ(t-vx) and x'=γ(x-vt)
with the condition t'=t.
The general result is:
x'=-x
t=t'=γvx/(γ-1)

Note that this synchronization procedure reverses the clocks so that the "leading" clock becomes the "trailing clock", but maintains the proper separation. Note also that for an infinite number of clocks this procedure would take an infinite amount of time.

Now, of course, we may not wish to be squished by undergoing a delta function acceleration, but the Lorentz transform is a linear operation in spacetime so we should be able to use standard signals and systems analysis. If the second clock's acceleration is considered the impulse-response of the first clock's acceleration then we can see by convolution that the second clock's acceleration will always be simply a time-delayed copy of the first clock's acceleration. I don't know how to prove that is correct, but that would be my guess.

-Dale

8. ### SingularityBannedBanned

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1,287
DaleSpam

are implying that we cant goto anderomeda galaxy in a single life time with near light speeds.

Form where the hell did this length contraction originated ?

9. ### ZephyrHumans are ONERegistered Senior Member

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3,371
Considering you posted a 'relativity buster thread', maybe you should research how relativity predicts length contraction. Know thine enemy and all that?

10. ### DaleSpamTANSTAAFLRegistered Senior Member

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Huh? What are you talking about? I didn't say anything about intergalactic rockets or the Andromeda galaxy. I wasn't even talking about length contraction.

Neddy and Pete were having a discussion about the synchronization of clocks that accelerate from one reference frame to another. Neddy seemed to think that if they all accelerated together they should remain synchronized and Pete seemed to think that they could not remain synchronized no matter how they accelerated. I simply derived the timing needed in order to mantain synchronization. Nothing more.

-Dale

11. ### c'est moiall is energy and entropyRegistered Senior Member

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583
Aren't "everybody knows-phrases" dangerous in regard to the truth? It's like "everybody knows the twin towers collapsed because of fire "...

12. ### SingularityBannedBanned

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But U seem to say contarary to what I heard since childhood that time slows down and hence we can go very far in single self life time ?
ie. while earth passes millions of years old.

13. ### SingularityBannedBanned

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1,287

I read that link, thanks, but it doesnt say why there is length contraction and
I did not understand the experiment.

14. ### DaleSpamTANSTAAFLRegistered Senior Member

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I simply said that if the clock at x=0 accelerates at t=t'=0 then other clocks need to accelerate at t=t'=γvx/(γ-1) in order to stay synchronized.

I don't know how you came up with relativistic travel from a post on the correct timing of accelerations. If I write X and you read Y then it will be very difficult to communicate.

-Dale

15. ### SingularityBannedBanned

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1,287
So U mean U didnt say anything about decelerations ?

16. ### RosnetPhilomorpherRegistered Senior Member

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681
Since this isn't the philosophy section, we can pass that.

17. ### c'est moiall is energy and entropyRegistered Senior Member

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Rosnet, you're full of crap.

18. ### CyperiumI'm always meValued Senior Member

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3,000
What is the problem with meshing them?

First we got to find the differences:

1: The scale (small - big).
2: Locality (probable - relative).
3: Time (flux - forward (also backwards = infinite energy = forward))

1) Doesn't really have mesh, we all know that things has different characteristics at a smaller scale (that's why you couldn't just make a miniature car without adjusting everything to that scale in order for it to work like the regular car, also it would be next to impossible to achieve the same speed relative to it's new size).

2) It isn't as important at that level, the locality of QT is probability relative to the SRT object, the law for the big here is allowing the probability of the QT to occur within it's grasp (or possibly without).

3) It would take infinite energy to move time backwards in SRT because of the huge amount of probabilities that would have to match in QT, the probability for everything in that object to move backwards in time would reach infinity which is the amount of energy required to actually achieve the work of stabilising so many probabilities to point at one direction.

--just an idea