[extropy-chat] unidirectional thrust

[scerir]

Alfio:
> The so called "vacuum" has a dielectric constant, 
> has a lot of weird spacetime and quantum properties, 
> now maybe it's full of dark energy pushing galaxies 
> far from each other. If there was some way to push 
> against it that wouldn't surprise me at all.

You mean to store energy in a rubber band 
between receding galaxies? The universal expansion 
might stretch it [1][2]. But to extract energy from such
a long rubber band, you need to re-shorten it. 
And that could be dangerous [3][4] :-) 

[1] Unless, during the expansion, the space itself, and 
the rubber band, would be essentially expanded too (?).
[2] The tension in the rubber band contributes to 
the stress-energy tensor.
[3] The galaxies will eventually cross an event horizon, 
and the rubber band will inevitably break, ouch!
[4] A too strong rubber band would cause a sudden big
crunch, or very fast blue-shifting.

(Dunno if the link below is about 
cosmological rubber bands, it seems so)
http://arxiv.org/abs/astro-ph/0104349