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The Twin Paradox

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_AVG_
Say you have 2 twins age 10 each.

Assume that one stays fixed at a point in space. (A)
Assume that the other starts moving at a speed of 0.6c where 'c' is the speed of light in a spaceship and returns after 8 years (assuming constant relative speed throughout ... 4 years away from his twin and 4 years coming back). (B)

Thus, according to Special Relativity, the time observed by A should be calculated with a Lorentz transformation, correct? So, B will come back 18 but A will think he is 20 even though they are twins!

HOW IS THIS POSSIBLE?
ocalhoun
_AVG_ wrote:

HOW IS THIS POSSIBLE?

Uh, you kinda just answered that yourself...
taytay
lol. agree'd
_AVG_
ocalhoun wrote:
_AVG_ wrote:

HOW IS THIS POSSIBLE?

Uh, you kinda just answered that yourself...


NO, what I don't understand is how one twin can be 20 years old while the other is 18? Then one will appear older than the other, right? HOW? Okay, suppose it's a smaller amount of time. Say only 4 years. Then B will appear 15 when he comes back and A will be 14 ... and you know that during puberty, every year brings a large difference in the physical appearance of a person. So, since B appears older than A, he will appear taller or maybe have more facial hair / pubic hair or something. How is THIS possible?
ocalhoun
It is possible, because time does not pass at the same rate in all situations. Time passes 'more quickly' for one twin than the other. What's so hard to understand about it?

Some of the things that relativity theory tells us are very strange, but that's only because we don't deal with them all the time.
Bikerman
_AVG_ wrote:
ocalhoun wrote:
_AVG_ wrote:

HOW IS THIS POSSIBLE?

Uh, you kinda just answered that yourself...


NO, what I don't understand is how one twin can be 20 years old while the other is 18? Then one will appear older than the other, right? HOW? Okay, suppose it's a smaller amount of time. Say only 4 years. Then B will appear 15 when he comes back and A will be 14 ... and you know that during puberty, every year brings a large difference in the physical appearance of a person. So, since B appears older than A, he will appear taller or maybe have more facial hair / pubic hair or something. How is THIS possible?

The question only arises because you are wedded to the idea that this is some 'trick' or some effect that influences clocks but not 'real' things.
Relativity is quite real - time passes at different rates depending on relative velocity (or gravity). It is not a trick. Suppose, for example, we stretch the point a little. I can't be bothered to do the exact math so I'll guestimate.
Imagine twin A (aged 30) sets off from earth at .9c and spends (to him) 30 years round trip. I'm guestimating around 2.3 for the Lorentz*- - which means his twin is perhaps going to be dead - certainly a very old man Smile

*You can calculate it yourself easily enough - 1/SQRT(1-v^2/c^2)
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