On Thu, 19 Feb 2004 13:17:36 +0100, Thomas Borchert
wrote:

Katherine,

Physicists call it "radiation pressure" and it's
measureable in a lab.


you can drive spaceships with it, though. There's a great scifi story
by Arthur C. Clarke about a solar yacht race using radiation pressure
from the sun on big "sails".

I've always wondered about the following:

Ok - so we all agree that a light puts out a small amount of force.
Newton tells us that an equal an opposite amount of force would be
directed in the opposite direction. F=ma.

So why can't we use high-intensity lights powered by a nuclear reactor
as a source of space propulsion? Is the F so small and the 'm' so
large that the 'a' would be miniscule? There's no wind resistance to
overcome in space, so you don't have to fight against that. I imagine
gravity would still be a factor though.

-Nathan