A common way to compute density is, of course, to take the ratio of an object's mass to its volume. But other types of densities exist, such as the resistance of somebody's brain to the imparting of common sense.

We already know the limits of Einstein's theories. From the centers of black holes at the very beginning of the universe - we call these singularities - Einstein's equations fail. In fact, people have joked that's where God is dividing by zero.

Photography is a form of time travel.

I suppose I can live with missing decimals, missing floors to tall buildings, and floors that are named instead of numbered. A more serious problem is the limited capacity of the human mind to grasp the relative magnitudes of large numbers. Counting at the rate of one number per second...to count to a trillion takes 32,000 years, which is as much time as has elapsed since people first drew on cave walls.

I dream of a world where the truth is what shapes people's politics, rather than politics shaping what people think is true.

Santa knows Physics: Of all colors, Red Light penetrates fog best. That's why Benny the Blue-nosed reindeer never got the gig.

We need more science in the world. Train me.