Apparently, and I don't really understand this, a Russian scientist claims time travel could indeed be possible! He says we might be able to cross the galaxy in an instant without breaking the laws of physics. He believes there are natural 'wormholes' in space, created by the tremendous forces after the 'big bang' and that these could act as shortcuts across the cosmos. It's all a bit beyond me but if it is theoretically possible, then presumably other civilisations could be using this 'galactic subway' to visit us. Just a thought.

Besom.

If you dispense with the distinction between space and time, as required by Einstein's theories, and think of them as a single continuum called space-time then this makes more sense. There is nothing to dictate that space-time should be flat - it could be folded. Imagine a piece of paper with an ant in the exact centre of one half who wants to get to the exact centre of the other half. If the paper is flat then he (or she) has no choice but to walk half to the length of the paper to the destination point. However, if (a) the paper is folded in two (with the ant on the outside!) and (b) a kindly (book?) worm has bored a hole right through both sheets then all the ant has to do is walk the short distance to the wormhole pass through to the other side and then walk the short distance to the destination point, thus saving him (her) self a lot of travel. If, instead of paper, the sheet is composed of space-time then 'the other side' could be anywhere in the universe, at any time, depending upon how the continuum is folded.

The trick will be to find wormholes that link the here and now to the where and when we want to get to! The major (theoretical) problem with this is that these wormholes are likely to be very small (sub-atomic scale) and short-lived. Apart from the obvious paradox of time travel - if I go back and accidentally cause the (young) death of one of my ancestors then I will never have existed to be able to go back in the first place! - there are many other problems to consider.
We are alive today because we have natural defences against the bacteria and viruses floating around.

Our ancestors would not have the same resistance and so we would probably kill them off by taking our bugs to them (see the first paradox). Also, we have probably lost resistance to bugs that were around then but have since died out - we would die too, even if we could find a way to not change history. Of course, there is nothing to say that time travellers are not changing history all the time. If someone killed my great-great-great-great-grandfather before he fathered children then not only would I cease to exist but every memory of me would also disappear (or, more precisely, would never have existed).

Perhaps there are an infinite number of alternative histories all of which are, in one sense (but not in our time), occurring simultaneously. Makes your head hurt a bit, doesn't it!

Dave