Why do you float in space?

What goes up must come down, right? Well, not in most places in the universe. If you have seen videos of the crew on the space station, you’ve likely seen them floating around doing flips up and down the hallways. But when you try to do a flip, you hit your head on the ground. What gives?! Well, most people would tell you it’s because we experience gravity here on Earth. While that’s the right idea, it’s not the whole weight of the matter.

Nearly everything in the universe experiences gravity, so long as the object has mass. But the space station is made out of stuff with mass, so why don’t the astronauts get sucked to the walls like we get sucked to the ground? Well, the force of gravity is related to how massive two objects are, like you versus the earth. Huge objects like the Sun and Earth have a lot of gravitational force. By comparison, the smaller space station and our even smaller bodies have very little gravitational force. So, the ISS (International Space Station) is still pulling the crew towards it and the crew is doing the same to the ISS. It’s just that these forces are so small they go unnoticed.

While the mass of the two objects “matters”, the distance between the objects is exponentially more important. The further the distance between the two objects the less force the two exert on each other. So, because the space station is 250 miles from the surface of the Earth, the amount of force the Earth puts on the station is far far smaller than what it puts on us standing on its surface. That’s why the astronauts can do those acrobatic flips with ease.

Now, back to that old adage of stuff coming down after going up. The universe is almost entirely empty space with such large gaps between objects that it is actually rare, in the grand scheme of things, for there to be significant gravitational forces in any area. So, I guess the correct adage would be “things that go up will come down so long as the mass of the thrown object and mass of the object it’s thrown from is sufficient and the distances relatively short.” But that doesn’t roll off the tongue quite as well.

By Chris Kelley