When I woke the next morning, I had to carry out some critical navigation. We had one shot to get back home, and I wanted to be on course from the beginning. While Houston kept an eye on us to make sure we didn’t stray out of a general path of certainty, I hoped to prove it was possible to navigate to and from the moon without their help. I was aiming for a narrow sliver of horizon on a planet tens of thousands of miles away, and there was no margin for error. This far from Earth, the tiniest changes in direction could result in huge errors once we had traveled the remaining distance in our voyage.
I used my sextant and measured the angle between Earth’s horizon and my preselected stars. However, I also had to choose the right place on the horizon. Our planet is about 8,000 miles across, and the horizon is only 50 miles deep. That sounds tiny, and it looked tiny from so far away, but 50 miles was too deep for what I needed to do. I needed more accuracy.
In my training, I had calibrated my eye for a specific part of the atmosphere. Between Earth’s surface and the blackness of space, the atmosphere looked like narrow bands of colors, mostly subtly different reds, magentas, and blues. On Earth I had experimented in simulations to identify a thin color line I could find consistently. I looked for a particular light blue within the atmosphere, and this reduced the 50-mile depth to a much smaller path as we left the moon. It worked even better than it had in the simulators: We stayed firmly on track.
We were still much closer to the moon than to Earth, but because our planet is so much larger, its gravity pulled on us more. We were now truly falling to Earth. It meant nothing to us in the spacecraft—there was no physical sensation of our incredible speed as we shot through the black void.
It was time for the three of us to float back into our spacesuits and help each other zip up before I went out for my EVA to retrieve film from cameras in the Scientific Instrument Module (SIM) bay. “You have a go for depress,” mission control told us. We slowly began to let the oxygen out of the cabin through a special valve in the hatch. Everything in the airless spacecraft looked the same, but I knew now that if I took off my helmet, I would die.
“We’re getting ready to open the hatch,” Dave reported. “Okay. Unlatch.”
“The hatch is open,” I announced. I poked my head outside and carefully mounted a 16-mm movie camera on the hatch to film my spacewalk. Then, grabbing the nearest handrail, I soundlessly floated outside.
I paused a moment and waited for Jim to poke his head and shoulders out of the hatchway behind me. He would stay there to keep an eye on me while I made my way down the side of the spacecraft. Other than our service module glinting in the sunlight, it looked really black out there. I looked down the length of the SIM bay. “You ready, Jim?” I asked. “I’ll work my way down.”
After 11 days in space, I was accustomed to weightlessness. With one hand on a handrail, I could turn my body with my wrist. The SIM bay was slightly to the left of the hatch, so I first needed to swing across the face of Endeavour. I let my legs float up, swung around, and worked my way down the side of the spacecraft, hand over hand, never using my feet.
I floated over the mapping camera, then rotated myself on the handrail, placing my feet in special restraints. I hadn’t really had a sense of where I was until this moment. Standing upright on the side of the spacecraft, attached only by my feet and the umbilical that loosely snaked back to the spacecraft hatch, I had a fleeting sense of being deep under the ocean, in the dark, next to an enormous white whale. The sun was at a low angle behind me, so every bump on the outside of the service module cast a deep shadow. I didn’t dare look toward the sun, knowing it would be blindingly bright. In the other direction, and all around me, there was—nothing. It’s a sensation impossible to experience unless you float tens of thousands of miles from the nearest planet. This wasn’t deep dark water, or night sky, or any other wide open space that I could comprehend. The blackness defied understanding, because it stretched away from me for billions of miles.