Time Travel Question (from A Briefer History of Time )

In summary, the conversation discusses a confusing scenario about time travel described in "A Briefer History of Time". It involves an event A happening on Earth and an event B happening 1 hour later on another planet 4 light years away. The possibility of traveling faster than light (FTL) to reach event B is brought up, and it is noted that to an observer moving away from Earth at near the speed of light, the order of events would appear reversed. FTL is considered unlikely and may lead to issues with cause and effect.
  • #1
Legendre
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Time Travel Question (from "A Briefer History of Time")

I read the original "A Brief History of Time" and is now reading "A Briefer History of Time". :P

There is a part about time travel that confuses me. Does anyone want to enlighten me using layman terms? (i am a mathematics major, not a physics major >_<) It is on page 108-109 of the book "A Briefer History of Time" in the chapter "Wormholes and Time Travel" if anyone wants to refer to it.

The scenario described is this:

1) An event A happens on Earth. 1 hour Earth time after event A, event B happens on another planet (Proxima Centauri, PC) which is 4 light years away.

2) Someone on Earth during event A can only get to event B if he is capable of faster than light (FTL) travel since B is 4 light years away.

3) To an observer on PC moving away from Earth at nearly the speed of light, it would appear the order of the events is reversed: event B appears to occur before event A. This observer would say its possible, if you could travel FTL, to get from B to A.
 
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  • #2
Yes, this is the kind of thing that occurs if you posit FTL. Cause and effect can get reversed, which is one of the reasons it is believed that FTL is not and never will be possible.

FTL will make your head hurt. :smile:
 

1. What is time travel?

Time travel is the concept of moving between different points in time, either forwards or backwards. It is a hypothetical concept that has been explored in science fiction and theoretical physics.

2. Is time travel possible?

Currently, time travel is not possible according to our current understanding of physics. However, some theories suggest that it may be possible in the future through the use of advanced technology and understanding of the universe.

3. Can we travel back in time?

The possibility of travelling back in time is still a subject of debate among scientists. Some theories, such as the theory of relativity, allow for the theoretical possibility of time travel to the past. However, many challenges and paradoxes arise when considering the feasibility of this concept.

4. What are the implications of time travel?

If time travel were to become a reality, it would have significant implications for our understanding of the universe and the laws of physics. It could also have major consequences on our perception of causality and the concept of free will.

5. How can we test the possibility of time travel?

Currently, there is no way to test the possibility of time travel as it is still a theoretical concept. However, scientists continue to explore the idea through theoretical models and experiments, such as the famous "twin paradox" in which a twin travels through space at high speeds and returns to find their sibling has aged significantly more than them.

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