On Thu, Feb 22, 2018 at 02:15:05PM +0000, Timothy Collinson wrote:
> Presumably not being allowed repulsion would preclude train type vehicles
> using that as their technology, but could you come up with something, maybe
> along the lines of a maglev but upside down.

Apart from nearby railings, can attractive-only artificial gravity
fields attract atmosphere above, or a few trillion cubic kilometres of
interplanetary gas, or stars?

A story I read once had a space drive that worked by using something
like a tractor beam on astronomical bodies.  The novel never went into
it, but lightspeed and distance did not appear to be limitations.
Presumably if you avoided nearby planets and stars, you could snag a
receding galaxy in any direction you liked.

It just occurred to me that this could also match E E 'Doc' Smith's
"Chaytors", described as engines that tap the energy of the expanding
universe.

- Tim