|MadSci Network: Physics|
Dark matter seems to clump together into areas that are also rich in galactic clusters. The overall gravitational effect sends galaxies and galaxy clusters orbiting at unrealistic speeds. Speeds that would, and should, tear galaxies apart. Dark Energy has been hypothesized as a type of Anti-gravity, in such that it seems to have a negative pressure affect on the universe; and is attributed to expansion by many scientists. Itís hard to say what either of them are, save for just interesting. I have previously only heard of dark energy outside of clusters, but I donít see why it couldnít be everywhere. The two types may offer equilibrium, in that one is pushing everything away from everything else, and the other is holding clusters together, countering expansion inside galaxies and clusters. This could explain why galaxies appear to get farther away from each other in all directions, but stars and planets stay tightly organized around galactic centers. A galactic collision is an awesome event, over grand timescales. If dark matter and dark energy exist, as they appear, they would certainly play a role in galactic collisions. These massive conglomerations of stars and gas are moving at relativistic speeds, stretching and bending space in complex ways. Under this idea, if a galactic collision displaced enough dark matter, dark energy may show its mysterious effects of reverse-pressure inside the collision.
New gravitational theories are incorporating old physics with new ideas; some that make dark matter obsolete. Here is an interesting article on dark matter. Many new ideas depend heavily on the existence of a particle called a graviton, but its existence is still hypothetical. Expect many changes to dark matter theories as we find out more about gravity. I find comfort in believing our physics is right, but history is replete with debunked theories.
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