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The Question

(Submitted March 26, 1997)

Can humans go back or forward in time ( in the future )? If yes then how?

The Answer

An interesting question....can humans travel back and forward in time. I presume that you are asking about travel in time like you see on television or in the movies. But let me take a more scientific (if simplified) approach.

The laws of science do not distinguish between the forward and backward directions of time -- yet they do distinguish the past from the future (time increases as disorder increases). There are some solutions to the equations of General Relativity which would allow for travel back and forth in time....(1) would require that you move faster than the speed of light, but we know that this cannot be done; (2) would require space-time to be very warped and a sort of "tunnel" between two space-time points to be present (called a "wormhole"). Such tunnels would not last long enough on their own for anyone to travel through them (unless the traveler discovered some way or built some machine which would keep the tunnel open). There are all sorts of other conditions which would have to be imposed on space-time in order for human beings to travel into the past. All of these conditions tend to conspire against time travel being more than a theoretical possibility. But, as of 1997, our understanding of physics causes the possibility of time travel to remain an open question. NOTE: What I have said here is related to big objects like humans...and my comments do not necessarily apply to very small (subatomic) objects.

Hope this helps,

Laura Whitlock
for Ask an Astrophysicist

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