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No, dark matter is something that happens within galaxies, affecting their rotation. It's not something outside.
by Florin_Andrei 12y ago
No, dark matter is something that happens within galaxies, affecting their rotation. It's not something outside.
- db48x 12y agoSorry, that's wrong. Matter, dark or otherwise, is scattered throughout the universe, with variations in density at all scales. Ordinary and dark matter are gravitationally attracted to each other, so they clump together. Anywhere you find matter you'll find a proportional amount of dark matter, on average; naturally there are variations. There's some in between you and your computer monitor right now. The first good indication that dark matter must exist was in fact that the rotation rates of the observable galaxies were too large for the amount of visible mater they contain. Of course the first explanation was that this matter was ordinary gas, dust, rocks, planets (which are just larger dust particles, when compared with the size of even a small galaxy.), etc that wasn't emitting any light. However, there would have to be so much of it that it would occlude the distant galaxies, something that obviously isn't happening. Thus the modern theory is that dark matter is a form of matter that interacts gravitationally with ordinary matter, but has no interaction with the electromagnetic force (light).