Is the Earth's net charge really zero?

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Discussion Overview

The discussion revolves around the concept of the Earth's net charge, questioning how it can be considered zero despite the influx of particles from the sun and other sources. Participants explore theoretical implications, the nature of charged particles, and the effects of the Earth's atmosphere and surrounding plasma.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that their physics book states the Earth has a net charge of zero and questions how this is possible given incoming particles from the sun.
  • Another participant clarifies that most particles from the sun are neutral, suggesting that any charged particles may cancel each other out.
  • A different viewpoint proposes a hypothetical scenario where charging an object and ejecting it into space could create a net charge on Earth, but speculates that atmospheric charge could replace it.
  • One participant argues that if the Earth gained a charge, it would attract opposite charges and repel like charges, leading to a return to neutrality, while suggesting that the Earth might carry a small, variable charge.
  • Another participant discusses the inter-planetary medium as a plasma, indicating that any net charge would be temporary and noting that exceptions to the no net charge rule exist.
  • A later reply mentions that due to the movement of electrons in plasma, the Earth might have a net negative charge, though the significance of this charge is uncertain. They provide a figure of around 400,000 Coulombs of charge for the solid and liquid parts of the Earth, while discussing the implications of the surrounding plasma's charge balance.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the Earth's charge, with some suggesting it is effectively zero while others propose that it may have a small net charge. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations in the assumptions made regarding the definitions of charge and the scope of what constitutes the Earth's charge, as well as the effects of the atmosphere and plasma interactions.

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My physics book says that the Earth has a net charge of zero. How is this possible with all those particles coming in from the sun etc, I would of thought it would accumulate a charge somehow.
 
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Which particles? Most of what comes from the sun is neutral (photons anf neutrinos). I would guess that there are enough positive and negative charged particles to cancel out.
 
Well what if you charged something up then shot it out into space, then the Earth would have a net charge but maybe charge from the atmosphere would replace it?
 
If the Earth gained a charge it would necessarily attract particles of the opposite charge and repulse particles of like charge and the charge would return to neutral. In reality, I'm sure the Earth can and does carry a small charge but it isn't constant and is negligible compared to the mass of the Earth.
 
If you think of the inter-planetary medium (the stuff between blobs like the Sun, planets, moons, asteroids, etc) as a plasma, you'll see that any net charge which any such blob had would be temporary (as Iron Sun X said).

Of course, as you explore the details ever more finely, you will find plenty of 'exceptions' to this 'no net charge' rule, including and especially that to an astronomer, 'temporary' can be a long time!
 
Because electrons move faster than ions in most neutral plasmas, anybody immersed in the plasma will tend to pick up a negative charge, especially if it is cooler than the plasma. The plasma temperature at the Earth's orbit is of the order of 100000K.

So, the Earth has to have a net negative charge of a certain amount. Is it appreciable - I don't know.

The Earth, not counting the atmosphere, definitely does have an electric charge. This charge produces an average vertical electric field of about 100V/m at the Earth's surface. But that mostly ends at the ionosphere. So given the Earth's size, the solid and liquid part of the Earth has around 400000 Coulombs of charge.

Going back to the second paragraph, there will be region of the plasma that has net positive charge that balances out the net negative charge over very long distances. So part of the problem is deciding how much of the plasma you count as "part of the Earth".
 

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