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

Congratulations on such an in depth entry. You have truly examined the issues involved, and left no stone unturned. "Timeline" by Micheal Crichton is a great book and examines many of the principals you have described. If you haven't read it I suggest you do.

I think what we really have to worry about is our grandfathers killing us in a preemptive strike. They wouldn't even have to travel through time, my Grandad only lives a few minutes away!

About the book Timeline:
I've read it. To be honest, I think there's a bit of a flaw in their logic. The whole double-slit based idea of parallel universes is fine by me; what I don't like is the fact that some universes run slower than others, or that some universes are "behind" others (I don't remember which the book used). I mean, if he wanted to argue that there is some constant which determines the "speed" each universe runs at, and that this value is different in different universes, then I would be OK with it, but he didn't try to explain, which was a bit annoying.

Other things I though were inaccurate:
- The "quantum foam" idea. I don't know, this may be established theory, but I'm not sure that wormholes are constantly popping in and out of existance at the quantum level. But whatever.
- The whole thing about shrinking down small enough to use quantum wormholes. Then again, this one is obviously a flight of fancy, so I won't bother furthur discussing it.
- Minor inconsistancy: Crichton apparently couldn't decide whether each parallel universe ran independently of one another. I think at one point he says that each universe is different, so if you go into the past and mess stuff up, it won't matter. But then, he does his (IMNSHO) thoroughly unsatisfying analogy to a baseball game to explain away grandfather paradoxes and the like. He even has a change made in the past affect the present at the end of the book. He should have been consistant and just stuck with a quantum-multiverse based theory.

Anyway, I'm aware that it was just a work of fiction; I definitely enjoyed the book.

PhysicsMan