Question: how is there no gravity in space

Angus Cook answered on 15 Jun 2016:

Good question, and a fun one 🙂

Gravity is a bit of a weird force, and we don’t fully understand it yet. The strength of gravity depends on two things: How massive the object we’re talking about is (size of an apple?, size of a bus?, size of the Sun?), and also how far away from it we are.

Gravity is stronger for more massive objects. Your pencil-case, for example, also creates gravity, but because it’s so SO tiny compared to (for example) the Earth, the amount its pulling you toward it is really REALLY small. We feel the Earth’s gravity because the Earth is really quite massive.

The other thing that effects the strength of gravity is how far we are from the object we’re talking about. The Sun’s gravity reaches the Earth (we know that because the Earth is kept in orbit around the Sun, orbits need gravity to work), but the effect of the Sun’s gravity on US is really really small because it’s so far away, compared to the effect that the Earth has on us.

So to answer your exact question: there IS gravity in space. Gravity goes a long long way (the Sun’s gravity, for example goes out at least as far as Pluto (we can tell because it’s in orbit around the Sun) and beyond. To find a bit of space where there was NO gravity you’d either need to go really really REALLY far from anything, OR find a bit of space where two planets (or Suns, or black holes) were pulling at you equally from opposite sides. Their forces of gravity would cancel eachother out, and you’d float right in the middle 🙂

So, why then (if I’ve said there IS gravity in space) do you see videos of astronauts floating above the Earth? Am I a big lair and wrong?
Well, not this time (I hope.)
Astronauts are actually FALLING all the time. The reason astronauts look like their floating is because the space station they’re on (with the camera in it to watch them) is falling too. Think of skydiving videos where the camera operator is falling with some other skydivers. If they’re all falling together it looks like the skydivers are floating.

So, why then don’t the astronauts smash into the ground, if they’re falling? This one’s a little trickier, but I’ll do my best.
The astronauts (and the space station) are going sideways around the earth REALLY fast, at the same time as they are falling toward it. I know if doesn’t seem like they’re going fast sideways, but try to imagine yourself in a car on the motorway. If the car’s at a steady speed (not going faster, or breaking) then you don’t actually feel how fast you’re going. Same idea on an aeroplane. When you’re cruising up in the air at a steady speed, you can’t feel that you’re going fast. Same idea with the astronauts.

If you go around the Earth fast enough, then while you are falling toward the Earth, the surface of the Earth is curving AWAY from you. If you get it right (and the astronauts have) then you can keep at exactly the same height above the Earth AND keep falling toward it forever.

Crazy, right? 🙂