Watch: What it would take to power the United States with solar energy

If the population of the world was only 100 people, what would society look like?

Joseph E. Stiglitz and Linda J. Bilme's exhaustedly researched book, "The Three Trillion Dollar War: The True Cost of the Iraq Conflict," breaks down the price tag, from current debts to the unseen costs we'll pay for years to come.

It’s easy to extend their usefulness by turning them into a flower pot, watering can, or pencil holder.

They are the most deadly weapon ever created by man. How many nuclear weapons are there? Who has them? Here are nukes by the numbers, the explosions and the destruction.

How does kissing affect our brains? Which way do most people tilt their heads? And how did the 'X' come to stand for a kiss?