Why does touching a past version of yourself cause a paradox?

Question

Why does touching a past version of yourself cause a paradox?
In sci-fi shows which involve the main characters travelling back into their own pasts, protagonists are often warned that touching their past selves will cause a paradox (for example, in the Doctor Who episode 'Father's Day'). If you accept that being part of your own timeline is possible without causing a paradox, why does the act of two versions of yourself from two different times touching cause one?

This is not my question someone asked this in the philosophy section but i want to know the oppinions for those in the physics section.

Answer 1

you cant travel back in time so the hole arugemt is mooted

Answer 2

Time paradoxes do not occur. If you travel back in time (an unlikely prosepect), no matter what do you or where you go. You have done it, will do it, and continue to do it. You where there, are there, and continue to be there.

You are a part of the space-time continuum, if you will, by which I mean a coherent "picture" of everything that happened, happens, or will happen, everywhere, forever. There is no way that you can "change" the future because that somehow suggests the idea of "prior" and "subsequently" into a construct that incorporates past, present, and future into a continous whole.

Answer 3

Yes you can travel back in time, it's been done before. The experiment was called The Philadelphia Experiment and some of the top scientists that ever lived worked on this experiment. You can also research The Montauk Project but beware the government has placed restrictions on the original site. To answer your question, if you are standing in a certain spot, can I come and stand in that same exact spot while you are still standing there? No.

Answer 4

If you touch your past self, you alter what they would do in life. If they do different things, that would lead to them not going down the same path as you did, and not going back in time at the same exact moment as you did. Therefore, how could you be there at all to do it? When you alter your history, you change your own past, which means the place you left isn't the same anymore, meaning you couldn't have come at that exact moment. So how could you still exist?

That's only a few problems with time travel and paradoxes.

Answer 5

Even if time travel to the past were possible, touching yourself would not necessarily cause a paradox. That was just a plot device in some stories.

Answer 6

The usual answer is because by contacting your former self you are changing the future of your past self, and therefore you may affect your past self's decision to go back into the past.

But as far as the wacko theories that are presented in movies like the Back to the Future series, it's just a convenient plot device to try to make things interesting.

Answer 7

The same matter can not occupy the same space when it is of different time. Since time travel is at most theoretical this was rule was made so filming such things would be easier (not having to have the same actor so close to himself).

Answer 8

Be cause the same matter can not occupy the same space at the same time, thus causing a paradox. Is it really science??? who knows, we won't know until it is tried.

Answer 9

because, it's not possible to be in two times at once. your physical being is always moving in time, and you always move FORWARD, to move backward is to erase what you've already done....