"No matter how much experience you have, there is always something new to learn."

"I fully expected that, by the end of the century, we would have achieved substantially more than we actually did."

"Science has not yet mastered prophecy. We predict too much for the next year and yet far too little for the next 10."

"I was always a little bit of a tinkerer, always trying to figure out how things worked."

"It was a surprise to me that we were able to bring back as much as we did."