I'm optimistic. I see no longer people accepting fuzzy thinking in the world. The change is not that people aren't still saying under-informed things. The change is that if you're in power and you say something under-informed, there are people out there with a voice who will take you to task for having done so

95, 96 percent of all that drives the universe has no known origin.

The history of exploration across nations and across time is not one where nations said, 'Let's explore because it's fun.' It was, 'Let's explore so that we can claim lands for our country, so that we can open up new trade routes; let's explore so we can become more powerful.'

I remain fearless of airplanes after 9/11. But during a trip to Los Angeles on a Boeing 767, I couldn't keep my mind from drifting: What's the largest piece of this airplane that could crash into the World Trade Center, explode out the other side, and survive intact? The landing gear? My computer battery? My belt buckle? My wedding ring?

Some memories are best absorbed through your eyes in real time, even if you have no record of it later. Because then you can access that memory and how you felt in that moment. If you're looking at your cellphone screen, taking a video of something that is otherwise unforgettable, watching it later will not recover the emotion you would have had, had you witnessed it directly.

The solar system should be viewed as our backyard, not as some sequence of destinations that we do one at a time.

... informed ignorance provides the natural state of mind for research scientists at the ever-shifting frontiers of knowledge. People who believe themselves ignorant of nothing have neither looked for, nor stumbled upon, the boundary between what is known and unknown in the cosmos.