Part of the show Q&A and What Does Derek Look Like?
Sam in Slovakia asked:
I was always fascinated with the state of weightlessness and how it works. A month ago I saw a report on artificial simulations of the phenomenon on CNN where people were on a plane and became weightless. How is it possible to nullify gravity in this way? Is it a question of zero acceleration or something like that? Is this how it works?
Weightlessness doesn't mean that there isn't any gravity. All it means is that everything around you is falling at the same speed as you. So if you were in a lift that was accelerating at g towards the ground, it would feel like you were weightless. So in the case of a satellite, it's falling all the time but misses every time it goes around the Earth. The way they do it in planes is that they make it fly on a parabola upwards and then make it accelerate towards the ground at the same rate as you would falling. So the plane is falling at the same speed as you so you feel like you're weightless. So it's all a question of relative falling.