Cesium, iodine from the Chernobyl reactor accident went around the world many times and everyone on the Earth has a piece of Chernobyl in their bodies, but it's very tiny - too small to cause much damage.

However, one new theory says that dark matter may be ordinary matter in a parallel universe. If a galaxy is hovering above in another dimension, we would not be able to see it. It would be invisible, yet we would feel its gravity. Hence, it might explain dark matter.

String theory is based on the simple idea that all the four forces of the universe: gravity, the electromagnetic force and the two nuclear forces, can be viewed, as music.

To a physicist, we have the 'I' word, the I-word is 'impossible.' That's dangerous.

Some people are a little bit afraid about the future because they see all these gadgets and gizmos coming down the pike and they think they're too old to learn all this new stuff. But eventually they begin to realize, 'Hey, some of this stuff is useful.'

We're headed for what is called Type 1 Civilization, planetary civilization. Type 2 would be stellar civilization, like Star Trek. Type 3 Civilization would be galactic, like Star Wars. We are Type 0. We get our energy from dead plants, oil and coal. But the question is: Will we make it? Will we make the transition from Type 0 to Type 1? It's not clear.

When we're born, we want to know why the stars shine. We want to know why the sun rises.