h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Given that pure time travel would not alter your physical position in the universe and the fact that the universe is constantly expanding; Is it theoretically possible that time travel is actually possible and there are in fact loads of successful time travellers floating about in space with very surprised looks on their faces?

You would be momentarily surprised to end up in outer space I suspect, but the shock wouldn't last long.

You'd need a machine like the to protect you from the elements.

We are all time-travellers, the older we become, the faster it goes.

Something to read: A398955

The T.A.R.D.I.S. is not a pure time machine, it is also capable of travel in the relative dimensions. I'm talking about a machine or method that just places you at a different point in time.

Assuming you could work out the relative expansion of the universe from your current position, perhaps if you travelled in the exact opposite direction at exactly the same speed, time (for you) would stop...

Traveller in Time on the
"Any self respecting time traveller should know there is no absolute position.

on the waves of time "

Time travel is a wonderful litterary device but I don't think it's possible in reality. Ever since Einstein mathematically expanded the three dimensions to four, others have (mathematically) supposed that you could travel in that dimension as well.

There are only three dimensions. All transible. Sorry, I made up that word, I think. Can't think of the real one.

Or someone could come back (forward?) in time and smack me in the head to correct me.

Waiting...

Waiting.....

Waiting..........

There are only three dimensions.

MisterHeritage is clearly assuming a time traveller can travel in time, but not in space, thus reappearing at the same point he left some time in the past or future. However, as the Principle of Relativity says, it is impossible to say if an object is stationary or moving smoothly, and so the idea of "the same point" in a different time period is ambiguous.

In an infinite universe you can only locate any point in terms of where it is relative to something else.

The only method that has yet been devised of time travelling is using a large rotating cylinder. The cylinder has to be massive, that is, containing a lot of mass. As it rotates, it bends spacetime around it in peculiar ways. If you travel in a loop around the cylinder, going very close in to it, into the region of warped spacetime, it is possible to travel either forward or backward in time.

The problem is that the cylinder must be very large - we're talking several times the size of the sun, so it is beyond our ability to build such a machine at the moment. But the theory seems to say that it is possible.

Gnomon,

I recently saw a piece on TV (UK), which said that someone had created a time machine using high powered lasers. 2 small techical hitches are that you can only move really really small things, and you can only send things back as far as when you turned the machine on.

So we should turn the machine on now, so that we can in the future travel back to the naughties and marvel at the peculiar fashions.

"so that we can in the future travel back"

I read somewhere that if time travel was possible, it would already exist, because people would have travelled back to our time (and before). So the fact that it doesn't exist already, means that it never will - one machine will never be built, the other someone forgot to feed the meter...?

You could always go back and feed the meter. Unless it's parked in a tow away zone. I think I saw The Doctor do that once. Where's Rita?

<>

Do we know for certain it doesn't exist? There is another theory that says it might be possible to send information back in time, if not matter. But if this was the case, and someone in the future wanted to try this, how would they know it'd been successful?

They would need to send back something that would be seen and recorded by the people around at the time. But this would be extremely risky; if people in the past got wind of the possibility of time travel, they would put more effort into research and thus change history.

So it would need to be something that would be recorded, but considered by the establishment as irrelevant or unsubstantiated and thus not change anything significant. The solution: ghosts.

The various time machines which have been postulated could not send anyone back to a time prior to the creation of the machine. (Science of Discworld III.) This could overcome the objection that if it worked at all, we'd see loads of spectators from the future at important historical events.

TRiG.

mpt true. The one whereby you essentially twist space time around a particular bubble would work. Theoretically it is possible. The only problem is that you have to isolate a region of space time fromthe rest of space time, reorient it then hook it back in. The energy required for this would be unrealistic. But theoretically it could work and you could go to anytime you wanted. As for any location, not sure. could end up appearing in the middle of planet earth, or in the middle of space as per the original idea.