Kelsey Johnson: The problem of light pollution — and 5 ridiculously easy ways to fix it

Ever gaze up at the starry night sky? This stunning view is at risk of disappearing -- unless we act now, says astrophysicist Kelsey Johnson. In this fascinating, unexpectedly funny talk, she explains how light pollution affects almost every species on earth (including us) and shares five 'stupidly simple' things you can do to help solve the problem.