Dark matter comprises over 80% of the universe

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Hello, all! I am no physicist, so please bear with me. I just read an article that stated that dark matter comprises over 80% of the universe. If this is true, why is it so hard to find? With that much stuff, you'd think we'd be swimming in it.
 

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  • #2
Drakkith
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Because dark matter does not interact through any of the fundamental forces except for gravity. Normal matter particles interact with other particles through gravitation, electromagnetism, the strong force, and the weak interaction. Without the latter 3, dark matter quite literally passes through everything else without being slowed. Even light just goes right on through it with no consequences. Since light doesn't bounce off of it or anything, we can't see it.

We could be swimming in it and you would never know.
 
  • #3
Bobbywhy
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Hello, all! I am no physicist, so please bear with me. I just read an article that stated that dark matter comprises over 80% of the universe. If this is true, why is it so hard to find? With that much stuff, you'd think we'd be swimming in it.

Actually, Dark Matter comprises only about 27% of all the mass-energy of the observable universe. It is not so hard to find either. Read the below Wiki page and be sure to check on some of the references used for the original papers. You'll see it is fairly easy to find, just hard to know what it's made of.
See: http://en.wikipedia.org/wiki/Dark_matter#Galaxy_clusters_and_gravitational_lensing
 
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Thank you for your reply.

So, that means that we cannot see, or feel dark matter in any way except by inference. May we assume that dark matter is then flowing through us? I find that concept a little hard to wrap my head around. I mean, if it is affected by gravity, shouldn't we be able to feel these particles in some way?
 
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Drakkith
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Thank you for your reply.

So, that means that we cannot see, or feel dark matter in any way except by inference. May we assume that dark matter is then flowing through us?

Sure.

I find that concept a little hard to wrap my head around. I mean, if it is affected by gravity, shouldn't we be able to feel these particles in some way?

Gravity is very, very weak. It would take a LOT of dark matter in order for you to feel it.
 
  • #6
phinds
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Also, you have scadzillions of neutrino's passing through you every second and you don't feel them either, although I do think they make my throat a little dry from time to time. :smile:
 
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Drakkith
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Is scadzillions a real number, Phinds?
 
  • #8
cepheid
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Is scadzillions a real number, Phinds?

It's certainly not a complex number. That would be ridiculous.
 
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phinds
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Is scadzillions a real number, Phinds?

Yes. It is 10 to the umpty upm. That's my story and I'm sticking with it.
 
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Drakkith
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Yes. It is 10 to the umpty upm. That's my story and I'm sticking with it.

Ah, so 10^umpty^upm.
 
  • #11
phinds
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Ah, so 10^umpty^upm.

no, 10^umpty-ump. That is, "umpty ump" is a singular phrase and its value is log base 10 of a scadzillion.
 
  • #12
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So, that means that we cannot see, or feel dark matter in any way except by inference. May we assume that dark matter is then flowing through us?

I would not make such an assumption. It appears dark matter is at least located in the vicinity of large astronomical objects like galaxies and clusters of galaxies. Whether there is any between me and my computer screen is conjecture. Since 95% of the matter/energy in the universe has only been recently 'discovered' we probably should await some further knowledge before making some assumptions. And don't rule out 'virtual' particles and 'anti matter'.....

Anti matter may have been consumed at the big bang such that scadzillions annihilated with 101 scadzillions of matter particles and our universe is a paltry leftover of real matter...'refuse' of creation. Add in virtual particles about which we do not have a complete understanding, which may also 'exist' all around us as quanta of non zero vacuum energy....well, whatever constitutes this universe, a lot seems way beyond most current science.
 
  • #13
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There is no way to determine what percentage of anything occupies the universe since there is no way to know what the hundred percent is.
 

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