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# How to stop time? Tweet

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1. How to stop time?
Hello everyone!!

How can we stop the time ,and if we move by the speed of light is that stop the time, and why?
2. Re: How to stop time?
You can't stop time, you can only greatly slow it down. Anything with mass can never reach the speed of light.
3. Re: How to stop time?
4. Re: How to stop time?
Well it's a difficult one as scientist are not to sure if time is a solid dimension or just a perception.
But if we are classing it as a dimension a general good measure if time is going forward is if the entropy of the universe increases. Entropy being the measure of disorder, and to stop it increasing you need remove all energy, only possible at absolute zero. Then you could say time has stopped.
5. Re: How to stop time?
(Original post by Lolicakes)
Well it's a difficult one as scientist are not to sure if time is a solid dimension or just a perception.
But if we are classing it as a dimension a general good measure if time is going forward is if the entropy of the universe increases. Entropy being the measure of disorder, and to stop it increasing you need remove all energy, only possible at absolute zero. Then you could say time has stopped.
Entropy causing the arrow of time is a fascinating concept, and what you say is essentially correct, but you miss a key subtlety:

For time to stop, from an entropic point of view, the entropy of the Universe must remain constant. This would require all processes to be perfectly reversible, which in practice is impossible (although theoretically possible). But to me it seems that this relation with entropy is only a vague arrow, not a direct law. If a certain region of space is undergoing a greater change in entropy than another region its perception of time isn't different. Couple that with many other problems and it seems, (at least to me), that the following must be true:

The second law of thermodynamics is a result of the directivity of time and not the other way around. Thus it cannot be an explanation for the directivity of time.

From a special relativistic viewpoint, time will stop if you move at the speed of light. For massive particles this requires infinite energy and so is impossible. The reason why this is true can be understood by the photon-clock thought experiment, which is a bit long to explain but accessible even to people who know little mathematics.
6. Re: How to stop time?
That Russian cosmonaut who spent 700 and something days orbiting earth is something like 0.002 seconds younger than he would have been having spent that time on Earth.

The only other way, apart from travelling at near light speed, is to orbit something like a black hole with enormous gravitational pull. I think?