Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asked at the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

55 years ago, Neil Armstrong and Buzz Aldrin became the first people to set foot on the moon,

and along with Michael Collins, rode Apollo 11 back to Earth, and opened the road from Earth to the stars,

in the hearts of the 650 million people who witnessed the landing, and the rest of us who

are born after.

While Neal Armstrong and Michael Collins are no longer with us, at age 95, General Aldrin

remains a living legend, and the work of all three Apollo 11 astronauts will be remembered

for ages to come.

But Aldrin's work to help with space neither began nor ended

with that mission. He is a governor of the National Space Society, and for many of our long-term

members, he is family, a fellow advocate and scientist working to pave that road to space,

who has developed many projects and led many efforts to help with that goal. We'll be focusing

on one of those projects today,

the Mars Cyclercraft, better known now as an Aldrin Cycler, a spacecraft able to carry large

cargoes back and forth to Earth, cheaply, and safely. I think it's easy for Buzz's work as a

scientist and engineer to get overshadowed by that historic

mission. After graduating from West Point in 1951, with a degree in mechanical engineering,

he would go on to fly 66 combat missions during the Korean War before completing his

doctorate in 1963 from MIT. His doctoral thesis was already on a space-bent, line of sight guidance techniques

...