[PatrickHenry]

Isn't gravity so weak (compared to electromagnetism and the nuclear forces) that it can be ignored in particle physics? Maybe F.'s effect only shows when a large mass is moving at 0.57+ c (?)

If you're really close to lightspeed, the increase in mass can get very significant. But, when you're dealing with neutrons, multiples of that still aren't much. I just don't know. Still waiting for one of the smart guys to help out.

[Marius3188]

How are we going to deal the small particles in space that are unseen from our start point?

I hit bugs going 70mph and I can't imagine hitting a rock getting up to .57c.

It sounds nice in a "clean" vaccum.