Science Questions

Why are planets, stars and subatomic particles round?

What’s the reason for the spherical nature of subatomic particles and atomic particles and planets and stars? Why’s everything round? Reg Bukari, South Africa

Ben: Everything isn’t round. Admittedly planets and stars and things are and a bubble of soap that you blow is as well. That’s essentially because tension pulls everything in and tends to make it spherical. If you’re talking about fundamental particles they’re not. When you see representations in a text book you’ll have a little round ball. That’s not what they’re like. They’re actually really weird. They travel as if they’re a wave. They get absorbed as if they’re a dot. It’s not really like a sphere and you’re talking about what’s happening at very small distance scales with quantum physics.

Chris: There was a paper in Nature recently where scientists were able to visualise hydrogen atoms with a stream of electrons. They were round balls.

Ben: yes, so a hydrogen atom isn’t fundamental. It’s made of a core and something orbiting round the edge. It’s a bit like a solar system and that does go round in a circle. There’s a force and it reaches equilibrium just like the Earth goes around the sun. It’s the same kind of picture.

Chris: What about the tiny bits inside? How do you know what shape they are?

Ben: You don’t they’re dots, they’re weird, they’re fuzzy and they’re quantum.

September 2008