"Life-Line" is a short story by American author Robert A. Heinlein. Published in the August 1939 edition of Astounding, it was Heinlein's first published short story.
The protagonist, Professor Hugo Pinero, builds a machine that will predict how long a person will live. It does this by sending a signal along the world line of a person and detecting the echo from the far end. Professor Pinero's invention has a powerful impact on the life insurance industry, as well as on his own life.
