"Narrator:: The heavens. Once an object of superstition, awe, and fear. Now a vast region for growing knowledge. The distance of Venus, the atmosphere of Mars, the size of Jupiter, and the speed of Mercury. All this and more we know. But their greatest mystery the heavens have kept a secret. What sort of life, if any, inhabits these other planets? Human life, like ours? Or life extremely lower in the scale? Or dangerously higher? Seeking the answer to this timeless question, forever seeking, is the constant preoccupation of scientists everywhere. Scientists famous and unknown. Scientists in great universities and in modest homes. Scientists of all ages."