 So get this. I saw a crazy advertisement on TV this morning. That weight loss mumbo jumbo again? Nope, a hotel. What's so crazy about it? It's orbiting around Earth. Oh, so it's a space hotel. Yep, the ad said you could float around because there's no gravity out there. Well, that's wrong. I know. Looks like we're going to have to go back into space and clear up some missing substance. I'll get my space suit. Hi, we're interested in a trip to your orbiting space hotel. I certainly just stepped... Hey, I remember you guys. What did I do wrong this time? You said that there's no gravity in Earth orbit. Well, there's not. People are floating around up there. There is gravity. You just can't feel the effects of it. I'm going to get another science lesson, aren't I? You bet. I gotta say, even though you don't know a lot about science, you got some really nice equipment. Right here, we're only about 370 kilometers... 230 miles from Earth's surface. Compared to the radius of the Earth, which is about 6,400 kilometers or 4,000 miles, that's a really small distance. And as a result, the force of gravity is almost as much as it is on the surface of the Earth. It's only about 10% less. But why are we floating? Gravity is pulling on us, but we don't feel its effects. Think about throwing a ball on Earth. I think we've got a human to help us demo this. Excellent. When you throw the ball, it travels in a parabolic arc and curves downward until it hits the ground. If you throw the ball harder, it travels farther but still curves in a parabolic arc. Now let's zoom way out and scale things up. Say that we're on top of a really tall mountain. And instead of throwing a ball, we're going to shoot it out of this cannon. Where did you guys get a giant cannon so quickly? We know this guy, you know what, that's not really important. We shoot the ball slowly and it curves towards Earth. In one of those parabolic arcs. Exactly. We shoot the ball a little faster and it goes farther. But it still curves back to hit Earth. Even faster, the ball goes halfway around the world. But it still hits Earth. When we shoot the ball fast enough, it still curves towards Earth. But the curve of the parabolic arc is the same as the curve of Earth's surface. So the ball is falling towards Earth, but it's going so fast in the horizontal direction that it never hits the surface of Earth. Ah, okay. So that's why my hotel stays in orbit and doesn't crash into Earth. My insurance company will be happy to hear that. Well, actually there's a really tiny bit of Earth's atmosphere up here and that's enough to cause drag. Drag slows down your hotel and lowers the orbit. So in a few years, your hotel will actually crash into Earth. But don't worry, you can use rockets to boost it higher. Okay, we'll deal with that in a sec. But getting back to the topic at hand, you still haven't told me why we're floating right now. Good point. The hotel and us and everything else on board are all falling around the Earth at the same rate. It's like a really tall elevator. Say you're at the top and the rope is cut. The elevator starts falling with us in it. Since we're falling at the same rate as the elevator, we can float around. Nifty. It's just like your orbiting hotel, except the elevator eventually crashes. Looks like you guys should stick to floating in space, huh? Ouch. So I shouldn't be advertising that there's no gravity in my orbiting space hotel? Nope, that's wrong. But I can say that people will feel weightless and float around free from the effects of gravity. Sure. And they won't crash into the Earth either. Not as long as you rig up those booster rockets. Well, this has been great. I've learned some stuff. You haven't put this company out of business like the last one, so thanks. You're welcome. We're happy to teach you an exchange for free trips to space. Wait, who said this was free?