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1

I won't answer on the energy part of the question, but here a few remarks which in my opinion are worth adding: The laws of physics are not frozen, the evolve (more precisely, they get more and more accurate ; e.g. Newton, replaced with the general relativity, etc.). Maybe one day someone will come up with an even more general theory, a part of which is ...


-1

Time travel is not impossible because of conservation of energy, time travel is not impossible at all. Entropy does not allow you to go backwards in time, but forwards does not present any problems.


9

Consider that most elevators have a counterweight to store energy. The counterweight isn't perfect, but it reduces the overall energy needed to move the carriage. As the elevator moves up, the counterweight moves equally down. Likewise, a time machine would have to overcome the energy deficit/surplus caused when moving from one point to another, but it ...


10

No, conservation of energy is for the entire system. If you can travel from time A to time B then both time A and B are parts of the same system as far as conservation of energy is concerned. Even if you assumed that despite travel being possible the times were separated, time travel would simply require the transfer of equal energy from in the reverse ...


15

It is true that general time-travelling violates conservation of energy. If you transport yourself into yesterday, you appear twice in the universe for that day, which means twice your rest energy, which is a lot of energy. It may mean that time-travelling is inconsistent and therefore impossible. But not necessarily. In general relativity, it is very hard ...


0

Hmmm, a very interesting question. Your logic seems sound, but I'm not a physicist, so I can't really say. What I can say as a non-physicist is that time flows in the direction of increasing entropy, so moving back in time would mean that the Universe should go back to a state of lesser entropy, which is supposed to be prohibited. Interestingly, this in ...


2

In principle, general relativity allows space-time to have non-trivial topology (wormholes) or dynamics (Alcubierre drive) that could be used to 'cheat'. However, it is very likely that such things do not exist (they violate some 'reasonable' assumptions about the universe, but without a predictive theory of quantum gravity, no one can say for sure); but ...


1

This alleged problem falls apart as soon as you do a rigorous analysis. It should be clear that with such random accidents there is no causation. If event A really causes event B, then that's reflected in the state of the system. You'll have a state of the form 1/sqrt(1+|u|^2)[|A B> + u |not(A) not(B)>], so an entangled state containing information about the ...


0

Many-world interpretation can be consistent with the second law of thermodynamics. It is not a problem. Now, about this hypothetical time travel: If you went back in time to tell Shakespeare about his work and he published it after, it looks consistent but it is ultimately a paradox because where does that knowledge come from? Information, or strictly ...



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