Yesterday, two American spacecraft flew within a foot of each other in orbit.

The same orbit. At the same time. Separated by twelve inches.

Gemini 7 has been up there for eleven days now, with Frank Borman and Jim Lovell aboard, when Gemini 6 launched yesterday with Wally Schirra and Tom Stafford. Schirra maneuvered Gemini 6 into rendezvous with Gemini 7 using orbital mechanics that I have been trying to understand from the newspaper explanations and mostly failing to follow at the level of actual calculation, but grasping in principle: you have to change your orbit to intercept another spacecraft, and the counterintuitive thing is that speeding up raises your orbit (which makes you go slower relative to a lower orbit), so the geometry of orbital rendezvous is backwards from what your instincts tell you.

They figured it out. Schirra flew Gemini 6 to within one foot of Gemini 7. They flew in formation for five and a half hours. The astronauts could look out their windows and see each other — four people in two tiny capsules, orbiting the Earth together.

Borman and Lovell are still up there. Fourteen days total when they come down. Two weeks in space. They’re going to beat Cooper and Conrad’s eight-day record considerably.

What the rendezvous demonstrates is the core competency for Apollo: find another spacecraft in orbit and close to within touching distance. For Apollo, that other spacecraft is the lunar module ascending from the Moon’s surface, and the astronaut in the command module has to find it and lock on and dock. This is the dress rehearsal.

Schirra and Stafford are back. Borman and Lovell come down Saturday. And they apparently serenaded Mission Control — Schirra played “Jingle Bells” on a harmonica he’d smuggled aboard, while Stafford played small bells. The timing, given it’s two weeks before Christmas, was perfect.

Two ships, one orbit. The Moon is getting closer.