Forty years ago today, Buzz Aldrin became the second man to walk on the Moon. Was that the outer limit of human capacity? Should we let robots take it from there or should we humans try to reach Mars? We talk with Buzz Aldrin and others. Also, tensions rise in Afghanistan, and I.F. Stone, once accused as a Russian spy, later celebrated as Washington's premier investigative journalist.
Banner image: Apollo 11 astronaut Buzz Aldrin on the moon