Al Worden is one of seven men who has been more alone than anyone else in history. He was the Command Module Pilot (CMP) on Apollo 15. While their companions were on the lunar surface, the CMPs orbited alone. On the far side of the Moon the CMPs were out of contact and further from Earth than anyone has ever been.

The BBC conducted an interview with Worden where he talks about the experience. One passage that caught my eye was Worden's thoughts on being alone:

I didn’t have to talk to Dave and Jim any more, except once they came around [when the orbiting command module was above the landing site) and I said “hi”. On the backside of the Moon, I didn’t even have to talk to Houston and that was the best part of the flight.

The whole thing is worth a read.

Image from NASA