The infinite variety in the properties of the solid materials we find in the world is really the expression of the infinite variety of the ways in which the atoms and molecules can be tied together, and of the strength of those ties.

When a liquid boils, the temperature has been raised to such a pitch that the evaporating molecules are sufficient in number and speed to lift off the air from the surface of the liquid and push it back en masse.

The difference between a gas and a liquid is that in the former, the atoms and molecules move to and fro in an independent existence, whereas in the latter, they are always in touch with one another, though they are changing partners continually.

Sound is a movement which is handed on from atom to atom in a gas through which the sound is passing, just as a chain of workers pass buckets of water to a fire. The quicker the workers move their hands and arms, the quicker the water moves.

I had been pursuing a Ph.D. in political science when my National Guard unit was sent to Iraq. Eight months into our deployment, in November 2004, a rocket-propelled grenade fired by Iraqi insurgents tore through the pilot's side of the Blackhawk helicopter I was flying.

The fossil fuel industry has taken control of, and powered up, architecture and methods originally built by the tobacco industry and others to attack and deny science.

I have been intimately involved in the techniques of genetic modification as a scientist since GMOs were first conceived. In that time, hundreds of studies and tests have been done on GMO safety - and we've seen no scientific evidence that GMOs are inherently more dangerous than crops produced by traditional plant breeding.

The most solid piece of scientific truth I know of is that we are profoundly ignorant about nature.