I have a physics question that I need some help with:
"Proxima Centauri is a star in the Alpha Centauri solar system, it’s the nearest star to our sun (4.24light−years) http://en.wikipedia.org/wiki/Listofneareststars. How large of a solar sail would be needed to accelerate a solar sail of mass m to a velocity which will get the ship to Proxima Centauri in two lifetimes?"
I'm assuming that the time is 160 years for 80 years each lifetime. Can anyone help?