Donald piniach asked:
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?
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, thatís gravity.
Kat - Right, itís gravity so itís not related.
David - It does explain why there are lightning discharges sometimes between the atmosphere and the ground. Thatís just a current pathway forming that lets the charge neutralise locally. Now, why do we have this charge imbalance? Itís very hard to understand and itís 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 thatís why we get a positive charge in the atmosphere because weíve lost a few electrons. I guess lightning discharges between the atmosphere and the ground locally redress that balance every so often. But itís very, very complicated. Because we regard the Earth as electrically neutral, thatís 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, itís 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 wouldnít recommend it.
I don't know the answer to this question but I'll speculate that the Earth as a whole is electrically neutral, give or take. Charge is leaving and arriving all the time owing to interactions with the solar wind, which deluges the planet with charged particles.
I know light passing through space has no net , I think the Earth has a net charge but the problem is it would be detected as neutral because the equipment for testing was devised in the environment and any setting of 0 would be unknowingly set to the equilibrium. So in simple terms 0 is not really zero, it is just an equal calibrated to the environment.
The universe tends towards balance. This is why symmetries go hand in hand with conservation laws. Charge is no different. While black hole do have a property of charge the more likely metric solutions appear to be uncharged. In other words neutrality wins the day since it is in balance. Others may have different views. jeffreyH, Thu, 30th Jun 2016