Re: Twins, deadbeats, and other relative subjects

Posted by Dale on Mar 04, 2002 at 08:57

Re: A follow up (dogrock)

The twin experiment: The one who travels comes back younger.

Yep. Done that and that is what happens.

Two rock experiment: One comes back smaller (both the shrinkage and time are related, can't imagine they are not, but correct me), if so the effect is also real.

Not quite. It doesn’t “come back” smaller. It IS smaller while moving but returns to “normal” size when it stops moving. But smaller is in the eye of the beholder. It is only smaller to someone who is watching it go past. If you sit on the rock, to you the size hasn’t changed. The same applies to the traveling twin who doesn’t see time changing.

The rock is really affected, does the rock resist this change.

Rocks just sit there. Rocks do not have the ability to decide to resist or to not resist. Does a clock resist slowing when it is traveling at a high speed?

e.g. What might happen to the electrons of the atoms when going in the direction of travel as away, do they not influence any viberations within the rock because of this.

Nope. They don’t have a clue what is happening to them. It’s all relative and it just happens. No decisions are made and no effects are noticed by the subject. It is only the “stationary” observer who sees the change. The twin doesn’t see time running slower. When the twin stops moving, time returns to “normal”. However the integral of the time effect is permanent so the twin comes back younger. The shape change of the rock is NOT permanent. There is no integral of the shape so the rock never sees the change and it comes back in the same shape it left.

When an apple falls straight to the ground, its world line is a curve, all planets travels in curves in their orbit, all objects in space travel in curves, except when forced not too.

No, they all travel in straight lines except when forced not to. The reason the apple curves is because the earth is rotating and the apple is moving sideways when it starts to fall. It falls straight toward the center of the earth which gives a curve just as you would see if you threw a rock sideways in the earth’s gravity. Without gravity the rock would have gone straight off into space and without the initial rotation the apple would move straight toward the center of the earth.

Planetary orbits are curves because of the force of gravity. All objects in space are subject to gravitational forces from billions of other objects. Close to the sun the force from the solar wind is even greater.

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