Question: Do balloons still float in space because on Earth they still float and there is gravity?

Columbus Operations answered on 15 Mar 2016:

Actually balloons have a tendency to fall slowly (when filled with air) or to raise slowly (when filled with a ligher gas – usually helium). And this happens because our atmosphere is denser closer to the ground and less dense the further from the ground you go. The balloon filled with helium tend to go up because the heliumis ligher (less dense) than the air around it. So the air around will push it up (just like if you put a buoy underwater, it will rise). And it will keep rising until the air around it thin enough that the helium and the air around it are exactly the same density. It will stay floating there until some of the helium escapes and the balloon will some down again (because the fabric around the helium is actually heavier than the air).

In space things are easier. There is no gravity. So there is nothing “attracting” the heavier gas down and leaving the ligher gas on the upper atmosphere. So what happens is that all the air is mixed around. Which means, balloons float even better in space. They don’t have a tendency to go up or down (or left or right). They will just float in place. Like astronauts do if they don’t push against a wall or hand rail.