Time Travel Question (from A Briefer History of Time )

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SUMMARY

The forum discussion centers on the concept of time travel as presented in "A Briefer History of Time," specifically in the chapter "Wormholes and Time Travel." It outlines a scenario where an event on Earth (event A) is followed by another event (event B) occurring on Proxima Centauri, which is 4 light years away. The discussion highlights that an observer moving away from Earth at nearly the speed of light would perceive event B as occurring before event A, illustrating the paradoxes associated with faster-than-light (FTL) travel. This reversal of cause and effect raises significant questions about the feasibility of FTL travel, reinforcing the belief that it may never be possible.

PREREQUISITES
  • Understanding of basic physics concepts, particularly relativity
  • Familiarity with the implications of faster-than-light (FTL) travel
  • Knowledge of the structure of spacetime and causality
  • Basic comprehension of astronomical distances, specifically light years
NEXT STEPS
  • Research the implications of Einstein's theory of relativity on time travel
  • Explore the concept of wormholes and their theoretical applications in time travel
  • Study the current scientific consensus on the possibility of faster-than-light (FTL) travel
  • Examine case studies of time dilation effects in high-speed travel scenarios
USEFUL FOR

This discussion is beneficial for physics students, science fiction writers, and anyone interested in the theoretical aspects of time travel and the implications of faster-than-light travel on causality.

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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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:
 

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