A lot of misinformation about earth and it being a sink is spread everywhere, including what I was taught in school, I hope you well-informed folk can help me out.

A sort of side-note, if anyone has a book recommendation explaining these kinds of concepts and everything related to them, please do let me know. It seems as if most books on electrodynamics don't really examine these assumptions we usually make. Examples: why earth is a 'sink' for electrons?; how, when grounding houses -- does a ground connection act as a wire which connects back to the same circuit, even when it's a single wire (taken from Ground wikipedia page) connected to ground? And the list goes on.

To quote my last question, I found it here: https://electronics.stackexchange.com/a/148684
Quote: "Current never ever ever ever flows to earth. It only ever flows through earth. Earth is just another wire - albeit a planet sized one. Electrons have to flow from one side of the power source back to the other. They can never flow out and never return." – Majenko

Moving on, the original question: Why aren't objects close to the surface polarized?
We know that by static inductance, when you rub two of the right materials together, one becomes negatively charged, and the other positively charged. Let's take one and get a neutrally charged material next to it, bringing it closer, we can see that it becomes polarized.

I've read that earth's surface is negatively charged, -500,000 coulombs, to be sure. So bringing a neutrally charged object close to it would make it polarized, is what I think is logical.

So why is my conclusion wrong, if it is wrong (doesn't seem right)? And why is it that earth is charged negatively?

  • $\begingroup$ Don't have an answer for all these, but lightning (like electricity) is driven by a potential difference. if the difference was not to the ground, it would not have come down in the first place but discharge to whatever it had built up the difference toward. $\endgroup$
    – Abel
    Commented Feb 20, 2021 at 14:36

2 Answers 2


Think of the electric current as a fluid, and a battery or some other source of current as a pump. Change the earth for the ocean.

I don't know about the negatively charged earth's surface, but those -500,000 coulombs are an absolute measure of charge. That charge is distributed over some surface, and the earth's surface is pretty big.


Yes, the earth has a field strength.

That page quotes field strength numbers of 300V/m or 150 newtons per coulomb. I've not bothered to do the equation for -0.5MC charge across the surface of the earth, but I expect it would line up with that.

The next question is why we don't notice this. I believe it's dominated by other effects; regular tribocharging can build up multiple-kilovolt charges on an ordinary human, and they don't notice until they touch a grounded object and get a small zap.


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