What is plasma?

Chris Smith received this question from listener Martin. It was over to physicist Jess Wade and planetary geologist David Rothery...

Jess - I think he is talking about the fourth state of matter. We’re all pretty happy with solids, liquids and gases, but if we heat gases up even more the atoms and molecules inside them start to tear apart and some of their electrons come off those atoms. And then you get left with this kind of sea of ions and also electrons on their own, and they’re superconductive.

And actually we do encounter the plasmas quite a lot; we have them inside a plasma ball if he’s ever seen a plasma ball, or we have them inside fluorescent tubes inside lights or you can get plasma displays for televisions now. So we do encounter plasmas a lot more often than you think.

Chris - David?

David - Yes. And the bepicolombo spacecraft will be studying plasma because the solar wind, the charge particles streaming out from the Sun are technically plasma, and there are a lot of plasma scientists that do a lot of work on space missions.

Chris - I’ve always wanted to ask Jess, a physicist, you know the plasma balls that you see actually how do they work and why does it love your hand when you put your hand onto them?

Jess - Because your hand is conductive because humans are slightly conductive. You have something at the centre of the plasma ball which is called a tesla coil and then you have a noble gas around it, and as those electrons go into that noble gas, and then you’ve got this plasma creating inside this ball. And you get these kind of fingers that come out of the middle, from the centre of this coil to your fingers if you’re physically touching the side of the ball because you’re partially conductive.

Chris - I thought it was just my attractive electric personality!

Jess - You’re also very attractive, but that’s a different story!