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You will need:
- One Traversable Wormhole (preferably macroscopic) about 1m in length (distance between the wormhole mouths)
- One Human-rated rocket ship capable of v~c speed (with supplies and fuel and suitable shielding of course)
- One Wormhole Grapple (ah... yes... how's that work then? Dunno), to be attached to the rocket ship
- One set of Inertial Damp(en)ers - lest the pilot be squashed
- A willing friend - ideally one who likes travel, for which reason I have selected Dean as Pilot to the Stars (please bring me back a hat from Alpha Centauri...)
- [Yoghurt pots and sticky tape are not strictly necessary, but you never know...]
Ensure the Wormhole Grapple is working and grab one end of the wormhole. Wish Dean luck and launch towards Alpha Centauri at high acceleration so that he very rapidly achieves 0.999998c... At this speed, and assuming the turnaround is quick at the other end (and that he doesn't spend too long haggling for the hat) Dean will be back in what seems to be about a week by his "clock" (just enough time allow him to catch up on some report-writing...) while 8.6 years pass on Earth (but... he'll miss the deadline, won't he? Not necessarily... read on)
Yes, we see the effect of time dilation as we look out of the window at Rocket ship Dean's tail-light... it was blinking once a second before launch, now it is flashing only once every seven and a half minutes.
But wait! Dean's got the wormhole with him... let's take a peek through that! Now, the wormhole is travelling with Dean... there is no relative motion and so, according to most authorities, Dean does not appear slowed down by a factor of 450 when seen through the wormhole. That's not lethargy - it's just intense concentration!
Half way through day 3 Dean looks up and says "I'm here!", nips out, buys a hat, and sets off home again. Three and half days after that he lands. We can see through the wormhole that he is indeed back - but wait! Looking up into the sky in the general direction of Alpha Centauri we see a very, very slowly blinking light. He's still on his way there!
How can this be? Is he indeed the Kwisatz Haderach? No... he's in the future. If he should so wish though, he can step back through the wormhole and as far as friends, family and deadlines are concerned he has been away for only a week, rather than, disappearing without trace for 8.6 years (c.f. "A Quick Trip to Budapest to do some Scribbling")
Likewise, we can go the other way and step 8.6 years into the future (bring back info on the future, clean up on long term investments and the lottery etc....)
No, I'm not making this up (well, not all of it...) here's a respected Professor outlining the same thing [NB I offer this link as it's the only one I know of that has a nice story - the same underlying principles are outlined all over the place]
Well... if you thought quantum mechanics was confusing now you can try getting your head around time-travel and all the attendant paradoxes...
But wait! Is it true? Er... no... or at least I don't think so. The problems are these (and I'm actually neglecting most of the practicalities):
Firstly, relativistic effects - Special or General - apply to separations in spacetime; they do not, as far as I know apply to spacetime. In fact I can't see how they could meaningfully apply.
Secondly, the effects as described would appear to be asymmetrical and suggest that in multiply connected spacetime (that's spacetime with holes in it) most conservation laws go out the window (e.g. if Dean sends me a pencil through the wormhole what 4-momentum (energy +3-momentum) does it have???)
Thirdly, even if a wormhole can move, how does it?
...
Thirteenthly, I forgot to supply a loo for Rocketship Dean.
These and other points will be addressed in due course. Is there a way of restoring equivalence to our inertial frames even in multiply connected spacetime... perhaps - in which case, no time machine can be formed in this way.
Warped space, warped thinking... Paradoxical Stuff.
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