"What will it take to explore a distant star within 100 years? To illuminate the momentousness (and ethics) of sending humans light-years from home, NASA scientist Les Johnson helps us digest mind-boggling numbers–the distance between stars, the energy required to travel that far–while laying out the opportunities and limits of existing technologies. Whether we get there by solar sails or ion thrusters or nuclear bombs, the advances we make in pursuit of interstellar travel will likely also change the way we live on Earth."–-Fionna M. D. Samuels, Scientific American