There's No Such Thing As Zero Gravity

Since we are on the subject of space, let's talk about the terms "zero gravity" and "microgravity." A lot of people use these two terms interchangeably and I hope that's just because they don't know what I'm about to tell you.

There is no such thing as "zero gravity."

Gravity is everywhere. Even in space.

Have you seen our solar system?

You have now

The force that's keeping every single one of those celestial bodies in orbit around our sun - that's gravity. Without gravity, everything you see above would just fling out aimlessly into space.

Let's zoom out a bit. Have you seen our galaxy, the Milky Way?

Hey look it's us!

The stunning spiral arms of that beast, and the disc shape, and the fact that all of those stars - including our beloved sun - are all held together so perfectly like that, it is because of gravity.

"But Angela," you cry, "why do astronauts float in space if there's gravity?"

Sit down and I will tell you.

Imagine you have a massive cannon placed right on top of the Earth at the North Pole.

Just use your imagination, okay?

Now, imagine if you shot a ball out of that cannon, and let's say that ball gets shot out at 100 miles per hour (or like 161 km/hr for you people in every country that isn't the United States). The ball would shoot out and then fall to the ground, like this:

If you were to try again and this time, manage to shoot the cannon ball at 500 miles per hour (or at around 805 km/hr), it would shoot out a little farther before falling back to Earth, like this:

Pretty close to making it all the way around the world! Let's speed this cannonball up. Let's amp this bad boy up to, say, 2,000 miles per hour (around 3,219 km/hr).

See what's going on here? The faster you launch out the cannonball, the farther it will travel across the Earth. So what's that sweet spot, what's the speed at which the ball won't fall back down to Earth, but will just orbit?

For Low Earth Orbit, that speed is around 17,150 miles per hour, or 26,700 km/hr. This is what would happen if you launched a cannonball out at that speed:

This is called orbital speed, and is the reason why astronauts float in space. Think of the International Space Station as the cannonball, a hollow one (just go with it okay?), and the astronauts are inside. By using the drawings above, and knowing that they are traveling around the Earth at around 17,150 miles per hour, we know that they are essentially "falling" around the planet, right? Like the ball is falling in all of the illustrations. It's not "floating," it's not doing anything super weird, it's just plain old falling, and missing the Earth every time.

Okay so you still don't understand why that makes people float up there.

Imagine that you're in Disney World on the Tower of Terror. If you've never had the privilege of experiencing this three minutes of sheer hell, they strap you to this giant, open elevator, shoot you up, and then let you fall at a speed greater than terminal velocity - before shooting you back up again and repeating the process until you've lost the will to live. This is the exact same mechanism that the astronauts are experiencing up there. When you're at the apex of the ascent in your elevator, just as you're beginning to fall, you feel your shoulders smuush up against your straps and you feel your body "float." This is the moment at which your body and the elevator play catch-up with physics before they realize IT'S FALL TIME.

The astronauts are in fall time ALL THE TIME.

That is why a lot of people experience Space Adaptation Syndrome, or Space Sickness, which is a really polite way to say "a lot of people vomit for a few days when they get into orbit." It's the exact same reason why people vomit on rollercoasters, 100% the same. So if you vom on rollercoasters, next time anyone makes fun of you, just be like "I'm training to be an astronaut."

Okay so gravity exists everywhere in the known universe, even though we don't quite know why.

But to say "zero gravity" in any context except describing a parallel universe is completely wrong. The proper term is "microgravity." If you hear someone who should know better use the term "zero gravity," they are either lazy or catering to the lowest common denominator. 

So go forth, oh educated ones, and correct the educational injustices!