type as me

When I was younger I read that Einstein (I think it was him, anyway) said something along the lines of:

Time travel is not possible because if it were then we would have already seen the travellers

This bugged me, as I thought that the statement didn't prove anything - it just showed that they haven't visited a period in our history yet. Although we may have existed for thousands of years, in the grand scheme of things out "history" may only be a tiny part of what is to come.

That in turn got me thinking, and I've come up with a theory as to why time travel does not work at all. It's only basic (and really rather obvious), and can probably be counter-argued with Data, Quarks, and other characters from Star Trek. For me, however, it makes sense.

Part 1 - Travelling Back in Time

Here is time:

I like to think of it as a line, only going forward because we can't find reverse. I have chosen two points on this line for my demonstration. Well shall say A is 0 AD, and B is now. I mean, now. Now. Ok due to the nature of time now is always changing so we shall call it present day. If you try this at home, you don't have to choose my dates, feel free to chose dates of your own - but not future dates (we shall address this later).

Hooray! I've built a time machine! What shall I do? I know, I shall go back in time! I shall choose a memorable date in the middle of my two points. Let's say 1066, and the Battle of Hastings.

This point will now be known as C. Let's say that I do travel from point B to point C.

By doing this, however, I have changed history. As soon as I have entered this time, and tried to stop King Harold getting one in the eye, I have created a new, completely different line. Instead of A to B, the timeline now goes from A to B₁ (via C).
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So what has happened to B? It has vanished. It never existed.

If it never existed I could not have gone back in time. It is a paradox that hurts my brain! The only way this would be possible is surely if the line C to B₁ co-exists with the line C to B, creating a parrallel universe. This would not be time travelling, as such, surely it would be universe travelling?

Part 2 - Travelling Forward in Time

Ok this one is much simpler. As I said before, I consider time to be a line:

As point B is "now", it is not static. It is constantly moving, and the line gets bigger. In front of B there is nothing. Nothing has been created. If nothing has been created, then how can you possibly travel there?

Conclusion

I don't know why I choose to share this but in my eyes it shows to some extent why I believe time travel not to be possible. I'm no genius (as is probably extremely clear) or physicist (again, blindingly obvious), but it represents my thoughts on the matter.