WATER.

Hey, Vsauce. Michael here. And I'm in London, right outside Buckingham Palace. Oh, I'm actually running a little bit late for tea with the Queen. Yeah, she's really into tea, but do you know what tea's mainly made out of? Water, and so today, we're going to talk about water.

Now, we all know that water is vital for life on Earth to exist and that water covers more than 70% of Earth's surface, but before we talk about liquid water, I want to talk about a culinary treat that occurs when you put a piece of bread on the ground, and then, at the exact same time, on the other side of the Earth, the exact geographical opposite point, you have someone else put another piece of bread— Earth sandwich. That's right—it's a challenge that was popularized by Ze Frank, and it turns out that making an Earth sandwich is incredibly difficult.

Why? Because of water. That's right. If you take a globe and you look at it so that France is right there in the middle, you're only looking at one-half of the Earth, but from that perspective, you are looking at almost 90% of Earth's dry land. It's all right there on that one side. It's known as the land hemisphere, and the other side, the exact other half of the Earth, is called the water hemisphere.

Now, you might be saying to yourself, "Okay, great. So Earth sandwiches are almost always soggy. Why should I care?" I don't know. But here's something that you should care about— the Three Gorges Dam in China, one of the largest hydroelectric dams ever constructed. Completed in 2006, and upon completion, it fundamentally changed something about Earth. You know how a figure skater spinning in place can slow down their speed by moving their arms out, by moving some of their body mass away from the middle of their body?

Well, the same thing can happen to Earth. The Three Gorges Dam did exactly what a figure skater does when they move their arms away from their center. It transferred 39 trillion kilograms of water 175 meters above sea level. NASA calculated that that massive amount of water moved caused Earth's rotation to slow down, so that every day of your life since that dam was finished has been longer by .06 microseconds.

It's not something that, for all intents and purposes, you have to worry about. If you are worried, you might be hydrophobic, but you're in good company— there are a lot of good hydrophobic materials, and they behave in some pretty cool ways. Hydrophobic materials are resistant to getting wet. That's right—they're usually made out of hydrocarbons that don't form good hydrogen bonds with water molecules, and because it takes more energy for the water to spread out on those surfaces, the water just sticks together.

It coheres to itself and forms nice little spheres. Now, in certain cases, super-hydrophobia occurs and it looks awesome. The leaves of the lotus plant do this and when water falls on them, the water just floats around like some big old blob of liquid mercury or something. It's a very bizarre trick, and I have you guys to thank for bringing it to my attention. In fact, it was that message that inspired me to do an episode about water in the first place, so thanks.

One final note on hydrophobia— it can happen in humans. And I don't mean being afraid of swimming or not liking the ocean— I mean an actual psychological aversion to the sight of water. Rabies is a virus that, if left untreated, can lead to severe neurological damage. In the late stages of rabies, the victim salivates constantly, but their throat and jaw become paralyzed, which means that the body cannot control the fluid in its own mouth and is in a constant fear of drowning.

This man has contracted rabies and is in the late stages of the disease. As he attempts to take a drink of fluid, his body recoils instinctively, as if the water might burn him. But thanks to vaccination efforts, the threat of rabies all over the world has been significantly reduced. Now, we could say a lot of other stuff about water, but I might save that for another episode.

In the meantime... And as always, thanks for watching.