Does the earth have an excess or deficit of electrons?

06 September 2016

Question

From the Milliken oil drop experiment, small excesses of electrons and their charges could be measured. It would be fantastically unusual if the number of electrons and protons on the earth, sun or galaxy was exactly equal given they were created independently (other than neutron breakdown) after the big bang. Heck even black holes have charge. So does the earth have an excess or deficit of electrons vs protons? And how many, approximately? Any idea if the universe has a charge?

Answer

We put this question to planetary scientist David Rothery...

David - Well, I admit to having had to look this one up. It depends whether Donald is talking about the solid Earth or the planet Earth including its atmosphere.

Kat - What are the differences then?

David - The ground beneath your feet does carry a negative charge. The atmosphere carries a positive charge.

Kat - So does that help to keep the atmosphere on?

David - No, that's gravity.

Kat - Right, it's gravity so it's not related.

David - It does explain why there are lightning discharges sometimes between the atmosphere and the ground. That's just a current pathway forming that lets the charge neutralise locally. Now, why do we have this charge imbalance? It's very hard to understand and it's defeating me but the positive charge on the atmosphere would be because the Earth is receiving charged particles from the sun all the time. Protons newly formed hydrogen nuclei, to go back to the previous question if you like, streaming along magnetic field lines towards the Earth. Some negative particles mostly electrons steaming along as well. So the charged particles going past the Earth are deflected by a magnetic field. But some particles, some electrons and our atmospheric atoms especially our outer atmosphere are stripped away in this solar wind. I think that's why we get a positive charge in the atmosphere because we've lost a few electrons. I guess lightning discharges between the atmosphere and the ground locally redress that balance every so often. But it's very, very complicated. Because we regard the Earth as electrically neutral, that's why you put an Earth wire to stop you getting electrical shocks. But it depends what your net positive or net negative charge is measured to the relative to. So, if you want a safe electrical conduct current going from your socket to your toaster, you want it to be neutral relative to the environment around you which is the ground. So although that is technically a negative charge relative to cosmos, it's all the same charge level as your toaster. So you can touch and get your toast without getting a shock.

Kat - That is a very good idea. So basically, we can't Earth the Earth though, can we, the planet Earth?

David - You could get a big wire and attach it to the sun I suppose but I wouldn't recommend it.

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