The crew of Apollo 11 faced risks that were literally out of this world. Engine failure could have left them stranded on the lunar surface or forever lost in space. Solar radiation and re-entry heat could have cooked them alive. A space-suit failure could have suffocated them in the most gruesome way. By today's standards, Apollo 11's technology was primitive — the onboard navigation computer contained only 74 kilobytes of memory, not enough to store a single MP3 music file. But as soon as Neil Armstrong took his first tentative step on the lunar surface, the risks were forgotten. For an all-too-brief moment, everyone on the planet was caught up in the thrill of human achievement, of a millennia-old fantasy come to life. Other lunar explorers would follow, but Apollo 11 was the first to take the giant leap for mankind.