The standard equation for centripetal acceleration in terms of angular velocity is IIRC:
a = (w^2 )* r
where a is the centripetal acceleration (let's say we want 9.8ms^-2, w is the angular velocity, and r is the radius.
Solving for w gives:
w = sqrt(a/r)
If we take for example a radius of 5km, this means we need an angular velocity of ~4.4e-2rad/s to get standard Earth gravity. This is about 0.5rpm.

As you can see, the gravity (or acceleration, to be pedantic) felt depends on the radius, which is the beauty of it. On an asteroid you could have a range of different gravity values depending on your position in the asteroid, from microgravity near the centre, to high values further away. To me, this would seem to be an ideal environment for space science and engineering to flourish.

As I mentioned, the problem would be to get the asteroid into a symmetric shape(well, not really shape as such, but symmetric in terms of mass) about it's spin axis. This is because (sorry, but my rotational dynamics is a bit rusty, so I can't go into detail) if the asteroid is not symmetric you get a non-diagonal inertia matrix. This probably doesn't mean much to most of you but it just means that the thing's spin will wobble and become unstable. However, I think that by the time we have the technology carry out the (admittedly rather daunting) task of moving an asteroid, getting the asteroid to be symmetric won't be too difficult.

I must also disagree on the point of living in low-gravity environments. Sure, I accept that it's probably fine to live in low g's, you'd probably even live longer, but what if you want to return to Earth? As far as I know there is a certain invisible line beyond which full recovery to normal gravity physiology is impossible. I don't think many people would be prepared to forsake coming back home ever again.

As for the issue of bringing materi�l to the asteroid, well, I'll just have to agree to disagree with you and say that it's necessary to bring a certain amount, initially very high, but decreasing as an infrastructure is built up.

The issue of the day/night cycle is something which I personally would consider to be fairly minor. Of course artificial lighting of some form would be necessary, but there are a lot of possibilities for generating and transmitting power in space, and fusion(high temperature fusion, not the unverified cold fusion) may not be as far away as you think. As far as I know experimental tokamaks have been making steady progress towards productivity, and plans for proper prototype reactors are underway.

Eclipse: I don't know much about that particular phenomenon, but I never heard anything about it being lethal. Have you any articles on it?

[ November 09, 2001: Message edited by: Jernau Morat Gurgeh ]