Interesting question for those who are interested (and have the know-how, which I lack). The question is as follows: How long would it take a square solar sail 10ft on every side and an undetermined mass (m) to travel from Earth to Alpha Centauri (4.134838 x 10^16 m away (1.34 parsecs)), assuming it begins with a velocity of 0m/s and is being hit directly with sunlight from behind?