A valid scientific theory is predictive, verifiable, and replicable. To me, that's beautiful.

'I resolve to eat less food' sounds good in theory, but it's often hard to sustain. And if you believe that it's all willpower, then you're likely to be upset with yourself if you don't succeed.

. . .a scientific theory is just a mathematical model we make to describe our observations: it exists only in our minds. So it is meaningless to ask: which is real, "real" or "imaginary" time? It is simply a matter of which is the more useful description.

Scientific theories are tested every time someone makes an observation or conducts an experiment, so it is misleading to think of science as an edifice, built on foundations. Rather, scientific knowledge is more like a web. The difference couldn’t be more crucial. A tall edifice can collapse – if the foundations upon which it was built turn out to be shaky. But a web can be torn in several parts without causing the collapse of the whole. The damaged threads can be patiently replaced and re-connected with the rest – and the whole web can become stronger, and more intricate.

I will say to you what the scientists say about the small particles in the universe: I can't show you where they are, I can only show you where they were.

A little dark chocolate in small amounts often helps lift me out of those blue moments. When I walk into my favorite store on Union Street in San Francisco that sells high-quality chocolates from around the world, I feel like, well, a kid in a candy store.