Gnargenox wrote:Source of the post Thinking negatively, is Dark Matter just static electricity?
Ah, no. Dark matter cannot have electric charge, or else it would interact with photons and we would see it.
Gnargenox wrote:Source of the post Created by the gravitational pull and spin created by normal matter coalescing on a galactic scale
We know that the formation of the dark matter halos preceeds the formation of galaxies, as this affects the appearance of the CMB anisotropies, and also the formation of the cosmic web. There is about 5 times more dark matter than regular matter in the universe, and the small density variations in the dark matter during the early universe gravitationally collapse first. Then the regular matter falls in to the gravitational wells produced by the dark matter. Regular matter collides with itself and can also radiate its potential energy away as light, thus enabling it to collapse into stars and galaxies.
The gravitational wells produced by the dark matter affect the appearance of the CMB by curving the paths of the CMB photons through it, and blueshifting (or redshifting) them as they fall into (or climb out of) the well. Since dark matter does not collide with itself, the size and shape of its gravitational well is different than the regular matter, so this makes an observable difference in the CMB which we can compare with simulations. There's an excellent video lecture explaining this physics in more detail, which I link here in the cosmology thread.
Gnargenox wrote:Source of the post I guess magnetic fields stretch as far as gravity does too.
Yes, the magnetic field has infinite range. But (at large distances from the source), it drops in strength according to the inverse cube of the distance rather than the inverse square. This is because magnetic fields arise from currents, and far from the source we can model that source as a "dipole". So in addition to the inverse square law decay which follows from geometry (area of spheres increase as radius squared), there is an additional drop due to the two "magnetic charges" of the magnetic dipole appearing to get closer together and cancelling out as you get farther away, just as with the electric field from an electric dipole:
Gnargenox wrote:Source of the post But every time I get a change to ask Richard Feynman "Why do magnets work?", he starts punching the wall
Feynman is ranting about the problems of asking "why" something happens in physics, or "how something works". It often comes across as very angry and arrogant, but I think he is actually making an extremely important point:
Actually Feynman is incorrect here when he describes why ice is slippery (the pressure is insufficient to melt it, if we compute and compare with water's phase diagram), but that's besides the point.
The point is, in the way I like to think about it, is that if I say I "understand" something then that means I know something about what's happening at least one level deeper than that. For example, I can say I understand that time passes more slowly near a massive object, because I know how space-time geometry is modified by a gravitational field, and I know how to use space-time geometry to compute time intervals measured by clocks carried by different observers. But I cannot say I understand why gravitational field modifies the space-time, other than by going through the derivation of the equations of general relativity.
Why do magnets work? I can honestly say that I don't understand why they work. I know how to compute the magnetic field, and I know how that field affects charges in its vicinity. I also know that magnetic fields are generated by moving charges. And I know that electric and magnetic fields are interrelated by special relativity. Why do they work that way? I don't know. "They just do, as shown by experiments." I similarly cannot explain what electric charge even is. All I can say is that it's a conserved quantity that generates electric field and causes predictable and measurable effects on other charges.
What is an electric or magnetic field, anyway? They are mathematical models we have built to describe and predict observed electromagnetic phenomena. But if you want to know why do those phenomena work that way? I cannot give you a satisfactory answer!