Does gravity decrease more slowly than other forces, or is it so weak that the gravity sources we feel are enormous and therefore have long radii of non-negligible effect, or is it something else?
The strong and weak interactions are only significant on very short distance scales; from the standpoint of "force laws" you can think of them as having an exponential decay with distance that makes them drop off to essentially nothing by the time you get to distances much larger than the size of an atomic nucleus. (That's an oversimplification, but it's enough to see why you can ignore them on astronomical scales.)
As I understand it, planetary magnetic fields influence solar winds; stellar ones structures in the galaxy; etc.
I’d really like to learn more (preferably, with numbers).
I know from talks that filaments[0], galactic lobes[1], structure of arms[2], etc relate to EM — but finding anything at the layperson level is basically impossible. Just short blog posts, but no real explanation of how this all relates or what drives it.
Harumph, I say!
[0] - https://www.livescience.com/radio-filaments-milky-way-center
[1] - https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=10918
[2] - https://blogs.nasa.gov/sofia/2022/04/05/make-no-bones-about-...
To hint at any role of E-M in the large-scale evolution of the universe is a good way to eliminate any possibility of a research grant. Probably this is just because the people deciding don't want to be obliged to learn how to evaluate whether the research program makes any sense. So, plasma fluid dynamics work normally is studied only at the scale of an individual planet or star, or at most a galaxy.
SOFIA, the telescope carried in a Boeing 747, lost its funding in part because mainstream astronomers found its unique capability of mapping magnetic polarization uninteresting.
Yes, I was oversimplifying somewhat. Magnetic fields don't affect things like the orbits of planets or stars. But they do have other effects on astronomical scales.
The plasma itself is magnetic, so the magnetic force itself is not acting over multi-light-year distances; the material carrying the magnetism is traveling over those distances and bringing its magnetism with it.
Also, this magnetism doesn't affect the orbits of planets or stars; my original statement was focused on what affects those things.
Maybe a better electromagnetic example would be radio signals from pulsars, which are enormous and travel great distances and still provide measurable signals even if they are light years away. We cannot on earth measure the gravity of these objects, nor the atomic forces, but we can readily meausure their electromagnetic sprayings.
I've never heard an explanation of the strong or weak forces that I actually "get" enough to understand their distance effects.
I thought this was excellent (in all ways) but particularly for your question: https://www.youtube.com/watch?v=UYW1lKNVI90
Edit: so for weak, I think I understand that "photons are massless, so are only subject to the inverse-square law; weak bosons have mass, so are also subject to decay". But that doesn't explain to this dummy how the strong force works, since gluons are also massless (... though mesons are not? but they're not fundamental).