# RTT’s mind boggling Time Dilation Paradox

1. Nov 28, 2004

### RawThinkTank

A train is moving relative to earth at such a high speed that the clock on the train slows down to half rate compared to clocks on earth. A rocket is launched in the opposite direction train is moving to such a high speed that the clock on the rocket slows down to half rate compared to the clock on train.

The rate of clock ticks on rocket compared to that of clocks on earth should be 1/4. So what do U think, Or Can U ?

2. Nov 28, 2004

### Fredrik

Staff Emeritus
Did you realize that this rocket is actually stationary in the earth's frame? The rocket is an irrelevant part of this story.

If the earth sees the train's clocks slow down by a factor of 2, the train will see earth's clocks slow down by a factor of 2. This may be surprising, but it's not a paradox.

You seem to be new here, so you probably don't know that there are lots of threads about this already. I suggest you use the search feature to find some of them and read them. You can e.g. search for "twin paradox", "time dilation" or "simultaneity".

3. Nov 28, 2004

### 4newton

I think this is a very good question.

If you go back in the direction of earth does you clock go faster and tick at the same rate as the clocks on earth or slower? Which direction can you go to have your clock run the fastest? How can this be if there is no absolute rest frame?

4. Nov 28, 2004

### Hurkyl

Staff Emeritus
In any inertial reference frame, stationary clocks run the fastest, relative to the time coordinate of the frame.

5. Nov 28, 2004

### Gamish

I dont see how this is a paradox, the rocket would simply be stationary to earth, or at least I think.

6. Nov 29, 2004

### AVNguyen

When you suggest this question(or paradox in your opinion) did you think about the relative speed between the Earth, the rocket and the train.In SR, i don't think it is right when you just simply add the relative speed of the rocket to the train and the relative speed of the train to the Earth to find the speed of the relative speed of the rocket to the Earth.
you know, it is not right when 2 things move toward each other with the speed of c, the speed will be 2c.That's ridiculous.

7. Nov 29, 2004

### AVNguyen

RawThinkTank
like fredrik suggested, i think you should find some threads that have the similar question like you.I myself found it's very intersting and useful in "is age relative" or "paradoxes".we have alot of discussions and problems there

8. Nov 29, 2004

### Fredrik

Staff Emeritus
9. Nov 29, 2004

### chronon

But in this case it works out OK. Using w = (u + v)/(1 + uv/c^2) to add velocities, if v=-u then the answer comes out at zero.

10. Nov 30, 2004

### AVNguyen

Mind you, we are talking about the case when the racket move so fast that the clock on the rocket slow down to the half rate compared with the clock on the train.therefore lvl>lUl, and even when v=-u, they can be equal to c.

11. Nov 30, 2004

### Fredrik

Staff Emeritus
I think I misunderstood the post that started this thread. When I wrote my reply I thought that RTT meant that in the train's frame the clock on the rocket slows down to half the rate of a clock on the train, but I realize now that he probably meant that this this happens in the earth's frame.

12. Nov 30, 2004

### Janus

Staff Emeritus
Actually, having run into this poster (RTT) before, I don't think that he even grasps the fact that there is a difference depending on which frame you choose. That's why he doesn't specify which frame. It is also part of the reason he believes this to be such a "mind boggling" paradox.

13. Dec 1, 2004

### RawThinkTank

The alien inside this train has two powerful telescopes; One for the rocket and one for the earth, He has shown me that the clock on the rocket has struck only 2:00 and Clock on earth has struck 4:00 simultaneously. I was shocked and ever since I have been posting this question on the internet in hope that my mind bogledness will be over.

14. Dec 1, 2004

### AVNguyen

You see,rtt.that's why Janus said you don't understand.Both of the alien's telecopes are in the rocket'stime frame.how can you expect them to be different.

15. Dec 1, 2004

### Janus

Staff Emeritus
The real problem here is that he doesn't provide enough information.
When and How were the Clocks originally synchronized?
What did they read when they were?
Did the train move with respect to the Earth between the time the rocket was launched and the clocks were synchronized?
If so, how far(or for how long) and as measured from which frame?

16. Dec 9, 2004

### RawThinkTank

so is there anybody here beyond human intellect ?

If so can any body tell me in words without numbers

" What is the TRIPLET PARADOX ? "

Last edited: Dec 9, 2004
17. Dec 9, 2004

### pervect

Staff Emeritus
no

[/quote]

[insert tongue in cheek]

Oh, this is probably just the triangle paradox. The triangle paradox is the paradox that the sum of any two sides of a triangle is (given some assumptions about the underlying geometry), always longer than the third side. So if you go from a to b, then from b to c, you travel a longer distance than if you went from a to c.

Mind boggling, isn't it?

Note that this is totally different from clocks - with clocks, when you go from a to b, and from b to c, they always read a shorter time than if you go directly from a to c in a straight line.

Rulers are sure weird, why can't they behave simply like clocks?

[remove tounge frome cheek]