At precisely 4:17 pm Eastern time tomorrow (July 20), it will have been 50 years since a spidery-looking American spacecraft named Eagle touched down on the surface of the Moon. Two hours earlier, Apollo 11 mission commander Neil Armstrong and Lieutenant “Buzz” Aldrin had left Colonel Michael Collins alone in their orbiting Command Module, as they began their powered descent to the Moon and to their indelible place in history.Armstrong and Aldrin set the Eagle down on a lunar plain called the Sea of Tranquillity in the nick of time. They had less than 30 seconds of fuel left by the time they touched down. Six hours later, Neil Armstrong emerged from the lunar module and slowly climbed down its metal ladder. With billions of people on earth watching live on TV or listening on the radio, Armstrong became the first human to set foot on the lunar surface, uttering those famous words: “That's one small step for (a) man, one giant leap for mankind.”Today on Midday, we discuss the legacy of Apollo 11’s triumphant mission to the moon with two distinguished chroniclers of America's space history: Tom's guests are Dr. John Logsdon, Professor Emeritus at George Washington University's Elliott School, and the founder and long-time director of its Space Policy Institute. He is also a former member of the NASA Advisory Council and its Exploration Committee. Dr. Logsdon joins us on the line from his office in Washington.And joining us on the line from the Hudson Valley in New York is filmmaker Robert Stone, the producer, writer and director of an extraordinary new documentary about America's decade-long race to Tranquility Base called Chasing the Moon. The documentary is currently streaming on PBS.org as part of its American Experience series. PBS will rebroadcast the entire 6-hour film on Saturday, July 20. Check your local listings.