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Q & A: Earth's gravitational and magnetic fields

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Most recent answer: 04/17/2013
Q:
Recently in my physics class, we have been discussing electromagnetism and earths magnetic field. My question is... How does electromagnetism hold atoms and particles together exactly? How does the Field not pull anything towards the earth? It is a magnet pretty much. Does earths magnetic field only interfere with objects that are like metal or magnified. But, if the magnetic field does pull objects towards earth wouldn't that relate to gravity. Is there any possible way the magnetic force on earth could relate to the gravitational force on earth?
- EB (age 17)
Augusta,GA, USA
A:

We've answered most of your questions in various threads on this site, i.e. . Search around for the long answer.

Here's the short answer: electromagnetism is strong enough on a short range that atoms are very stable when arranged in a crystal or other dense structure. The details within a specific structure are complicated, but in general it is the attractive forces between opposite charges which hold together molecules and atoms.

On a small scale, these forces are significant. The forces fall off very rapidly over a long scale, however, since positive and negative charges mostly cancel each other out. So, electricity and magnetism become weak very rapidly for large-scale phenomena (like the earth's fields).

Gravity is a completely different force. In addition, there are no "negative mass" objects to provide repelling forces with gravity, so gravity doesn't cancel out over long distances. This is why the earth's gravity is important, but it's electromagnetic fields are less so.

David Schmid


(published on 04/17/2013)

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