|MadSci Network: Physics|
As far as we can measure, the Universe is charge-neutral to at least 1 part in 10,000,000,000,000,000,000. How do we know this? Well, electromagnetism is actually much stronger than gravity (like trillions of trillions of trillions of times stronger). That's why your muscles can lift an object against the gravity of the entire Earth (compared to the size of the Earth, your muscles are puny!) So, if there were a significant charge imbalance in the Universe, its effects would be easily noticeable, but no non-gravitation forces have been observed in the dynamics of galaxies or clusters of galaxies.
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