The chunks of comet Shoemaker-Levy 9 were so large, and were moving so fast, that each hit Jupiter with at least the equivalent energy of the dinosaur-killing collision between Earth and an asteroid 65 million years ago. Whatever damage Jupiter sustained, one thing is for sure: it's got no dinosaurs left.

Today, scientists sound the alarm on other environmental dangers. Vested interests still hire their own scientists to confuse the issue. But in the end, nature, will not be fooled.

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.

If each dead person became a ghost, there'd be more than 100 billion of them haunting us all. Creepy, but cool.

Intelligent life can't be all that common because it's really rare on Earth and especially since we define ourselves to be intelligent. But in the eyes of an alien coming here who has the technology to make it here, they might observe us and conclude that there's no sign of intelligent life on Earth.

I have thoughts every day that are themselves tweets.

When I was a kid, I thought that if everyone looked up the way I did then everyone would want to study the universe just like me - how could they not? This naiveté is what tells me that my interest was more a calling than a rational comparative assessment about what to be when I grew up.