If you built a time machine, went back and did something?

Question

and then came back to the present, then decided to undo what you just did, how would you go about it? Do you go back just before you did it and stop yourself or what?

But if I went back to a time just before I went back the first time, would I not exist the first time and so anything I did from that moment now won't happen because I've taken myself from that time and went forward to that times future. Put it another way, I haven't done anything tomorrow so if I go into the future 2 days time, I couldn't do anything yesterday unless I go back to the day before yesterday.

Answer 1

You could always travel back to just before you travelled back and stop yourself from travelling back in the first place. This of course doesn't allow for the creation of a paradox in time.
What you would have to do to avoid this would be to travel back as you say to the point in time just before the time you travelled back to and lock yourself in a room to prevent you from doing what ever it is you did.
This of course throws up another problem in that if you are locked in the room you may not be able to travel back to the future to decide that you didn't like what you had achieved in the original time shift, also you wouldn't therefore be able to travel back to lock yourself in.
In answer to your question, not sure.

Answer 2

I think the easiest solution would be to go back to the time before your first trip into the past and leave yourself a letter explaining to yourself your reasons for the trip to be cancelled, and the events that will occur if the trip takes place.
As long as you know that the letter will be read and adhered to, then you could travel back to your present time.Making sure to take your trip before your earlier self reads the letter,and without ever having to have met your earlier self.
So, ok you may blink out of existence when the letter is read, but the earlier you that has just read the letter would carry on and create a new time-line, without your former ****-up.

Answer 3

The simplest, but not terribly efficient way, is to go back to just before you went back the first time. If you never went back, then you don't have to undo anything. BUT you get a paradox. If you never went back, then why would you "go back" again to stop yourself the first time.

Answer 4

Why not just come back 5 minutes before you left the first time, and decide not to go back?

Answer 5

You'd be creating a paradox .. so unless you subscribe to the theory of parallel universes your deeds would neither be factual nor reversible .. paradoxically if you invented the time machine it would be difficult to go back before the invention since the invention would not exist to re-transport you back to the present

Answer 6

This is what happens when you watch the Back To The Future marathon too many times in a row.

Answer 7

honesty i dont believe humans can travel through time. to do that, they would have to go at least the speed of light. if time travel were real, why arent there any tourists from the future visiting from the past or some people going to the past and trying the change the future? why isnt my great 100 times grandkids visiting my family from this era?

Answer 8

paradox

if you went back in time and changed your own future then you couldnt have gone back in time, so what would you stop.......

which is why time travel is such a mental teaser.

and to throw one right back at you, if you could go back in time and kill Hitler, would you? before you say "of course" think about it, how different would thw world be without the stuff that was invented BECAUSE of WWII?

Answer 9

id go back and slap you for youre silly answer to discrimination. For a start its obvious that disabled people need to park closer to the shop, as a lot of em cant walk properly

Answer 10

no you go back to just before your duplicate self went back the first time and convince your duplicate self not to go back to do anything that you would later have to go back to prevent from happening..paradoxically if you convinced your duplicate self not to go back to do something ..you wouldn't be going back to convince your duplicate self not to go back..so it's status quo..or add infinitum..so the moral is don't take time to mess with time..