There's a tremendously satisfying freedom associated with weightlessness. It's challenging in the absence of traction or leverage, and it requires thoughtful readjustment. I found the experience of weightlessness to be one of the most fun and enjoyable, challenging and rewarding, experiences of spaceflight. Returning to Earth brings with it a great sense of heaviness, and a need for careful movement. In some ways it's not too different from returning from a rocking ocean ship.

The energy varies with the square of the velocity, so if you need five times the velocity, that's 25 times the energy.

The life expectancy of people going to Mars may be decreased by the higher level of radiation that they receive.

We have the ability, at such high fidelity, to simulate the physical world through computers. But when the spiritual world or human behavior comes into play, we don't have a very good model for that at all.

Dwelling on an engine failure for a pilot as he rolls down the runway is NOT what he should be thinking about - it's obtaining a smooth liftoff! But in the back of his mind, he knows exactly what to do (or pretty much) and in many cases, if he's alone in the fighter aircraft, he has to leave that aircraft in an ejection seat in a big hurry!

My Sunday mornings are spent in a recovery meeting in Pacific Palisades.

Once you've been first, it cannot be done again. Not by you, not by anyone else.