One night, my friend Richie and I were watching PBS at about 3am. There was a fascinating program on about the creation of Earth [from a scientific standpoint, of course]. When it came to the origin of the oceans, the theory they presented was that massive meteors composed primarily of ice crashed into Earth. A lot of meteors. So many that when they melted, they covered almost the entire planet with water. Voila, oceans! However, as they pointed out, some disagree with this theory because the ratio of regular water [H2O] to heavy water [HDO] in our oceans is different from the ratio in all observed ice-meteors.
STOP. Back up. Heavy water? What the heck is heavy water? HDO? In the ocean?
We could barely pay attention to the rest of the show. Why hadn't we ever heard of heavy water before? It was mentioned so offhand, like EVERYONE knows what heavy water is. I began formulating conspiracy theories about all the world's secrets being revealed on PBS at 3am when no one is watching. The next day, I looked it up.
Heavy water, or HDO, or deuterium protium oxide, is water that contains higher levels of the isotope deuterium than normal, or light water.
Okay... so what does that mean?
Basically, it ain't water. In experiments, fish and other creatures placed in very high concentrations of heavy water dropped dead, and small mammals became sterile after drinking too much of the stuff. It only exists in small quantities in ocean water and has to be separated through distillation to be used. And what is it used for...?
Oh yeah. Nuclear weapons.
I am so not kidding. It's also used in nuclear power plants and other nuclear-type things. Something to do with plutonium? I'm not sure. But it all sounds very exciting and dangerous to me. In fact, the original Flash supposedly got his superhuman speed after inhaling "heavy water vapors." Cool, huh?
Actually, before you start snorting seawater, here's what heavy water will actually do to you: probably nothing. If you drank nothing but pure heavy water for a week or two, you'd eventually get sick and die, but since pure heavy water in that kind of volume is pretty hard to come by, it's kind of a non-issue. In small quantities, ingesting heavy water is totally harmless. Iranian Nuclear Chief Mohammad Sa'idi even thinks it could cure cancer and AIDS! You can read about that more here, but I wouldn't get your hopes up.
So in the end, heavy water is just some weird kind of water that won't give you super powers but probably won't kill you either. And from now on, I'm keeping one eye on PBS.