Question: how can hydrogen produce uptrust in a small condensed space

Paul Brack answered on 13 Jun 2015:

I’m not sure if I’ve understood your question right, so please let me know if I’ve answered the wrong thing!

The reason why hydrogen gas floats upwards is that it is much lighter than air – you see exactly the same effect with helium in helium balloons; if you let them go, they’ll float off into space.

So if, like in a Zeppelin, you attach somewhere to sit to a really big balloon of hydrogen, and add in some way of steering it, you can fly to places! The lightness of the hydrogen will pull you up, so you don’t need any other method to produce upthrust. To come back to earth again, you just have to let hydrogen out of the balloon until the weight of the place for people to sit is enough to pull the balloon downwards.