Wikipedia:Reference desk/Archives/Science/2019 June 16

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June 16

Does the universe have an electric charge ?

That is, does the number of protons and electrons equal one another, or are there more protons, giving the universe a positive charge, or more electrons, leading to a negative charge ? And if the number is roughly equal, is there some regulating force that causes this, or is the reason unknown ? SinisterLefty (talk) 13:04, 16 June 2019 (UTC)

This question has been asked at Quora where various replies depend on assumptions about the size of the Universe. If the universe is finite, then it seems impossible to have a never-ending electric field line, so it seems that a finite universe must be charge neutral. If the universe is infinite, and has a uniform nonzero charge density through its infinite expanse, then it has an infinite net charge. Then every part of the universe is a source of some never-ending electric field lines. DroneB (talk) 13:26, 16 June 2019 (UTC)

standard cosmological model works like the universe has no net charge. If it had, the repulsion between same charge would need to be taken into account to explain expansion of the universe, which is not done AFAIK.

see also: electric_charge#Conservation_of_electric_charge

Also, the universe seems conductive enough to act like this (from Electrostatics#Electric_field):

The electrostatic field (lines with arrows) of a nearby positive charge (+) causes the mobile charges in conductive objects to separate due to electrostatic induction. Negative charges (blue) are attracted and move to the surface of the object facing the external charge. Positive charges (red) are repelled and move to the surface facing away. These induced surface charges are exactly the right size and shape so their opposing electric field cancels the electric field of the external charge throughout the interior of the metal. Therefore, the electrostatic field everywhere inside a conductive object is zero, and the electrostatic potential is constant.

Gem fr (talk) 16:19, 16 June 2019 (UTC)

So, are any theories proposed for what would explain this exact match in the number of protons and electrons ? SinisterLefty (talk) 19:22, 17 June 2019 (UTC)

Not sure you need to explain that, because this is the simplest solution you can imagine, and you'll some symmetry breaking for the number to be different. But don't trust my word on this, this math is far above my grade. Gem fr (talk) 19:54, 17 June 2019 (UTC)

There are other charged particles than protons and electrons so the net charge can be zero without a perfect match of those particular particles. And a proton is a composite particle composed of three valence quarks: two up quarks of charge +2/3e and one down quark of charge –1/3e. PrimeHunter (talk) 20:30, 17 June 2019 (UTC)

Thanks all. SinisterLefty (talk) 18:09, 23 June 2019 (UTC)