Throughout history, people have used many methods to clean their teeth. Some ancient people chewed on frayed twigs. Others rubbed their teeth with cloth or swabbed them in vinegar. The Egyptians may have been the first people to use toothpaste when they mixed powdered pumice (a porous rock formed in volcanic eruptions) with vinegar and applied it to their teeth in the 100's B.C. Some toothpastes still contain pumice, but science has since supplied other toothpaste ingredients that the ancient Egyptians never dreamed existed.
Mushrooms -- they're not just a pizza topping. This psychotropic fungus has guided many an adventurer on a trip. How do shrooms make their magic?
We first reported on the possibility of an invisibility cloak last year. Now a different invisibility cloak is making the news -- one that uses metamaterials to redirect light away from the wearer.