Weird question about Time dilatation... pls see details?

Question

Time slows down for fast moving object relative to an observer, isn't it that the observer is also moving as fast relative to the object? Then the time dilatation must cancel itself, right?

Answer 1

Time dilation occurs when two people (frames) are moving with respect to each other. If they continue their motion, yes, EACH person will see the other person's clock run slower! It seems like a paradox, and, in fact, this intuitive problem is called the "twin paradox." It goes something like this:

Suppose Albert and Henry, identical twins, set up an experiment. Albert takes off in a spaceship and heads away at a significant fraction of the speed of light. He coasts straight out, stops, turns around, then coasts back at the same speed. When Henry sees video of Albert's clock while the spaceship is coasting, he sees Albert's clock is running slow. At the same time, when Albert sees video of Henry's clock, he sees Henry's clock runs slow by the same amount.

The problem is, when Albert returns, they find out that Albert is significantly younger than Henry. What's more, Albert's clock confirms that it has run off less time than Henry's. How can this be if they both saw each other's clock slow by the same amount? It does not make any intuitive sense.

The answer is that Albert and Henry did not move identically. Henry stood still, but Albert had to accelerate to his cruising speed. While he was accelerating, he was not in an "inertial frame." Simply put, if you feel acceleration (or gravity, for that matter), the simple laws of Special relativity no longer apply.

In fact, the answer to the twin paradox lies in examining what happens during these acceleration and deceleration phases. If you do some thought experiments, you will see that when Albert is coasting away, Henry's clock appears to run too slow. But when he hits the brakes to stop, all of a sudden during his decceleration, he sees Henry's clock speed up all of a sudden, MORE than making up for the time it had been running slow. In other words, if Albert sees Henry's clock behind his by an hour, when he stops, it will rapidly spin ahead an hour plus a bit more.

Conversely, when Henry watches Albert's clock as he slams on the brake, he will see Albert's clock slow down even more, so that Albert's clock will run even SLOWER than he would have calculated from when he was coasting.

On the return trip, the same things would happen all over again. The key point is, to compare their ages, you need to get Albert and Henry sitting still compared to each other. If you try comparing their ages while they are still moving, comparisons and simultaneous events have no meaning. Since Albert was the one who accelerated and deccelerated, he is the one who ends up younger. It is those acceleration and decceleration phases that are the answer to the twin paradox--they are not really identical "twins" at all, since only one of them had to accelerate.

If the experiment were instead done so that BOTH Albert and Henry got on spaceships and headed in opposite directions at the same speed, then returned, then the result would be that they would both be the same age, despite seeing the other's clock being slow--in this case, their clocks would resyncronize once they both stopped. However, they would BOTH be younger than someone who stayed home.

Hope that makes sense. Read up on the Special Theory of Relativity--it is easily understandable, as opposed to the General Theory. If you can find it, there was an old PBS series called "The Mechanical Universe and Beyond" that include a terrific visual presentation.

Answer 2

This paradox shows that special relativity is not quite right. Einstein came up with 2 theories of relativity, Special relativity and General relativity. Your "weird question" is very weird if you only consider special relativity and when Einstein published his paper in 1905 he knew of this problem. It took until 1907 for him to figure it out.

The answer is acceleration and gravity. He realised that acceleration and gravity were one and the same thing (this he called his "happiest thought" and this was the solution to his problem.
The object passing the observer has been accelerated to its fast speed and it is this acceleration which has changed the time for the object. To figure out the maths behind it it took until 1915
This new theory is General relativity and is the most accurate theory of gravity humans have come up with.

Answer 3

A good observation. Measurements have (apparently, taking it on 2nd hand reporting, here) shown particles lasting longer than "our" time frame would allow, the only explanation being that they are longer-lived due to relativity (they are moving close to light-speed and live longer than we would expect.) But on the face of it, you are right: two trains, approaching each other at different speeds, would have a common averaged velocity of approach and should show equivalent phenomenonological results. Too bad Albert is dead, he could probably help, here!

Answer 4

No. Both observers have a 'normal' time in their own inertial reference frame, and see the others time as 'slowing'.

Take a course on Special Relativity to really understand it.

Doug

Answer 5

The well deeds that you just do won't will let you pass off track to your subsequent lifestyles. True, you'll be born to your subsequent lifestyles in a faith in which they'll hate Hinduism, however the samskars ( the karma of your earlier lives) will once more deliver you again to the right course. P.S Why do you fear approximately the following lifestyles? As you mentioned that you've got advanced slightly bit on this lifestyles, why can not you check out to arrive the target on this very lifestyles?

Answer 6

the idea is that u are racing with time.. for example light with time......... well u can e-mail me 'cause i have to go now .. [e-mail]