ech (07/02/82)
Minsky remarks that light pressure is inverse square, but so is the force of gravity; that, to a first approximation, is of course true. However, the force of the sun's gravity is NOT the issue: delta-v is. Using the light sail to KILL momentum (so you can come back) is just as important as using it to gain momentum, and the change in momentum is exactly proportional to the force applied, which remains inverse-square. =Ned Horvath=