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lastofsix
2007-Jun-12, 04:18 AM
I have a question:
How are astronomers certain that dark matter is not regular matter, like blackholes, planets, dust, and burnt-out stars? Current theories of dark matter just seem so strange. Would'nt it be simpler if dark matter could be explained without such strangeness?

Thanks
Eric Jones

nauthiz
2007-Jun-12, 04:06 PM
It's called dark because it doesn't interact with other matter in any known way other than gravitationally.

If it were traditional matter, we should see it giving off stuff like electromagnetic radiation. Or blocking out electromagnetic radiation from sources behind it.

Clarification: We aren't sure it isn't "traditional" matter - but since we can only detect it by observing gravitational interactions, we can't be sure it is traditional matter, either.

KingNor
2007-Jun-12, 04:34 PM
if i understand it correctly, dark matter only even exists in theory anyway.

i mean, dark matter is the simplest explanation to strange observations, not the other way around. Scientists don't make up wacky explinations to account for dark matter. The strange things are already going on, and dark matter is the theory they use to explain the strange observations.

In any case i suspect that the dark matter theories are just a place holder until scientists can figure out what is really going on. or.. maybe dark matter is really an exotic material hard for us to understand.




A question i've got about dark matter though, isn't the milkyway full of dark matter just like every other galaxy? so what ever dark matter is, it's got to be all around us right now too. right?

John Mendenhall
2007-Jun-12, 05:15 PM
A question i've got about dark matter though, isn't the milkyway full of dark matter just like every other galaxy? so what ever dark matter is, it's got to be all around us right now too. right?

Yes, that's the idea behind trying to detect dark matter particles here on Earth. I don't particularly care for the dark matter approach, but there doesn't seem to be any other explanation that works. Whatever it is, the hunt is enjoyable.

nauthiz
2007-Jun-12, 05:31 PM
if i understand it correctly, dark matter only even exists in theory anyway.

There's some observational evidence (http://www.badastronomy.com/bablog/2007/05/15/hubble-finds-dark-matter-smoke-ring/) for it.