Earlier this week, I went to a screening of Discovery’s When We Left Earth: The NASA Missions, a six-part HD history lesson on our space program with never-before-seen, remastered footage that premieres June 8. Amazing. The kind of amazing that makes your mouth drop open and your head turn to the person sitting next to you to make sure that they’re seeing what you’re seeing.

Here are three reasons, from episode 2’s Gemini missions, why you need to tune in…

(1) The first American spacewalk: Gemini IV astronaut Ed White (below) steps outside the capsule and flies at 17,000 mph, 200 miles above the Earth, for 36 minutes. He “didn’t hear” the commands to come inside sooner.

(2) Rendezvous: To test pilotability, essential for a lunar landing, two spacecrafts, Gemini VI and Gemini VII (below), find each other in orbit and fly in tight formation, as close as six inches, for 270 minutes. The astronauts see each other through their windows. And wave.

(3) Learning to work in, and with, zero gravity: How hard is it to maneuver when weightless? Gemini IX’s Gene Cernan finds out when his heart rate rises to 170 bpm as he crawls, hand over hand, to the back of his capsule. After finally strapping in to the jet pack waiting there for him, he’s too tired to fly it. Gemini XII’s Buzz Aldrin (below) trains for his mission underwater to simulate a zero-gravity environment, and becomes the first astronaut to complete the simple tasks that NASA has designed to test man’s performance in space. He makes three trips outside the hatch, spends more than five hours walking in space, and never breaks a sweat.