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What is Dark Matter?

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posted on May, 29 2015 @ 02:20 PM
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But would you agree that interstellar space no longer seems as empty as once thought? And if not normal matter, then what? You seem to have a good grasp of the topic.
a reply to: Astyanax


edit on -05:00pmFri, 29 May 2015 14:28:30 -05003102285 by Parthin because: more thoughts.

edit on -05:00pmFri, 29 May 2015 14:29:23 -05003102295 by Parthin because: misspelling




posted on May, 29 2015 @ 04:59 PM
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a reply to: Parthin


But would you agree that interstellar space no longer seems as empty as once thought?

No, I'm afraid I don't. Why do you think this is the case?


If not normal matter, then what?

The presence of dark matter, whatever it is, is indicated by certain gravitational effects: the deflection of light by strong gravity fields, which can be seen through telescopes, and discrepancies in the apparent mass and rotational speed of galaxies. Gravity is a property of matter, therefore the unknown cause of these gravitational effects was dubbed 'dark matter' — 'dark' because it did not appear to absorb or emit light, or to interact with ordinary matter except gravitationally.

As Arbitrageur pointed out in his detailed post, there are lots of different ideas of what 'dark matter' actually is. He is more knowledgeable about these things than I am, so if you want to know what dark matter is according to those theories, you'd best ask him. I really don't have an opinion; since I do not know the subject well, I am in no position to have one.



posted on May, 29 2015 @ 08:15 PM
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a reply to: Parthin
a reply to: Astyanax
Thanks Astyanax, I do have opinions but I'm no expert like ErosA433.

Whether empty space is empty is a loaded question. Our models suggest that even without any regular matter or dark matter, empty space is not really empty because it contains "vacuum energy" which we suspect is probably also what we call "Dark Energy" or at least related to it, and this turns out to be most of the mass/energy content of the universe, maybe 74% according to this:

chandra.harvard.edu...


So even with nothing in it, empty space is not really empty according to quantum field theory.

When you consider the matter we know of, like hydrogen, we suspect the density is something like 1-2 hydrogen atoms per cubic meter in interstellar space. If there's 8 times as much dark matter in other particles, the equivalent of 8-16 hydrogen atoms per cubic meter still seems pretty empty to me, as it's probably better than the best vacuum we can make on Earth. So "empty" is a relative term which is hard to interpret. Scientists get more specific, like stating the number of hydrogen atoms per cubic meter, or the quantity of neutrinos passing through a given area.

Even with all that dark energy filling up the void as we suspect, the mass/energy density of the universe seems low to me because, space is almost inconceivably vast.



posted on May, 30 2015 @ 01:31 AM
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a reply to: Arbitrageur


Whether empty space is empty is a loaded question.

It's empty, but loaded...

Since this thread is about 'matter', I thought I'd omit mentioning vacuum energy and dark energy. They mostly tend to confuse people who lack a science background.

Parthin, the baryonic mass density of 'empty' interstellar space is as Arbitrageur states, and as he says, this is a harder vacuum than anything we could possibly create on Earth. Interestingly, though, this almost nonexistent mass is sufficient to rule out interstellar travel at near-light speeds, because at relativistic velocities even a collision with a proton would cause damage to the spacecraft. Something as big as a speck of dust would probably annihilate it entirely.

Even if this problem could be overcome (one proposed way is to propel a mountainous iceberg before the spacecraft), there's a much harder one to deal with. As the spacecraft moves closer and closer to c, light from sources along its direction of travel gets blue-shifted to higher and higher frequencies. The ship will fry as a result.


edit on 30/5/15 by Astyanax because: of impingent gamma photons.



posted on May, 30 2015 @ 09:31 AM
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We will not travel to the stars at relativistic speeds. Instead we will warp space to get there. We already know space can be warped.
reply to: Astyanax



posted on May, 30 2015 @ 12:28 PM
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a reply to: Parthin

Do we? I wonder.



posted on May, 30 2015 @ 06:17 PM
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here is my take on this.

If we assume that building blocks of matter, possibly quarks, were formed at the moment of big bang, and all of them were formed (finite number) then it is easy to derive that not all of them, probably majority of them, turned into elements. Building blocks vastly out number those building blocks that found 'right' bind with other blocks. But elementary building material is always available and zipping freely filling up cosmos.

Building blocks, quarks, perhaps, that did not find a bind are still in abundance every where around.


As to what makes 'building blocks' to form in harmonic group resulting in atom nuclei ask a pro.)))
Hope it is already known and me just catching up on my own... as a philosopher))).

cheers board

DO



posted on May, 31 2015 @ 05:31 PM
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originally posted by: Arbitrageur
a reply to: Parthin
a reply to: Astyanax
Thanks Astyanax, I do have opinions but I'm no expert like ErosA433.

Whether empty space is empty is a loaded question. Our models suggest that even without any regular matter or dark matter, empty space is not really empty because it contains "vacuum energy" which we suspect is probably also what we call "Dark Energy" or at least related to it, and this turns out to be most of the mass/energy content of the universe, maybe 74% according to this:

chandra.harvard.edu...


So even with nothing in it, empty space is not really empty according to quantum field theory.

When you consider the matter we know of, like hydrogen, we suspect the density is something like 1-2 hydrogen atoms per cubic meter in interstellar space. If there's 8 times as much dark matter in other particles, the equivalent of 8-16 hydrogen atoms per cubic meter still seems pretty empty to me, as it's probably better than the best vacuum we can make on Earth. So "empty" is a relative term which is hard to interpret. Scientists get more specific, like stating the number of hydrogen atoms per cubic meter, or the quantity of neutrinos passing through a given area.

Even with all that dark energy filling up the void as we suspect, the mass/energy density of the universe seems low to me because, space is almost inconceivably vast.


WOW, and you guys have measured the whole Universe and came to this conclusion ??
I think your calculations and models are wrong and that is the one and only reason for anything "dark" needed.




posted on May, 31 2015 @ 05:36 PM
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originally posted by: Parthin
There have been attempts to explain the "missing matter" as some kind of special particle, but what if this dark matter is ordinary matter? Let me explain. We're pretty sure the Oort cloud contains uncountable smaller bodies as far as the Sun's gravity can reach. But what's beyond that? Interstellar space. And interstellar space is....empty? But what if it's not as empty as we think? We have found planets that are not part of a star system. And we have observed that smaller bodies are numerous, whereas larger bodies are few in number. So maybe, interstellar space contains countless, unseen small bodies, like in the Kuiper Belt and the Oort Cloud, instead of being empty. This would account for the mass that our telescopes cannot see. Non-luminous chunks of rock, frozen gas, and ice, with a temperature of absolute zero, held loosely together by gravity. Even enough of just hydrogen could hang together to form a small planet, with nothing to disturb it. OK, I know we have some physics people on ATS, what do you think?


Dark Matter and Dark Energy are variables in mathematical equations. Nothing real !
There was no need for those before, but we observed the Universe and some stubborn scientists didn't wanted to change the old wrong model to fit the reality, so instead they added new stuff to make wrong theory work again.



posted on May, 31 2015 @ 08:55 PM
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originally posted by: KrzYma
I think your calculations and models are wrong and that is the one and only reason for anything "dark" needed.
What's the "right" model?



posted on Jun, 1 2015 @ 02:51 PM
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a reply to: darkorange


If we assume that building blocks of matter, possibly quarks, were formed at the moment of big bang

They didn't, though. It was a few trillionths of a second before that began, and a few millionths of a second before it was over.



posted on Jun, 1 2015 @ 09:10 PM
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thanks for the link

But that's not exactly the point I wanted to make.

Quarks are good candidates because, in my humble opinion, they
are building blocks of atom nuclei and they never been directly observed or found in unbind state.

Another point I wanted to put forward (obviously some one thought of that for sure long time ago) is that all possible number of the building blocks (possibly quarks) were created during Big Bang (no more are being created after) but only a tiny portion of them found binding states to form elements.



posted on Jun, 1 2015 @ 09:14 PM
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Imo your post is good, but wt kind of expert is eros? Just curious.
a reply to: Arbitrageur



posted on Jun, 2 2015 @ 12:39 AM
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a reply to: Nochzwei
Read his thread on dark matter detection where he explains the work he's doing in that area. I posted a link to it earlier in the thread here.



posted on Jun, 2 2015 @ 04:20 AM
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originally posted by: Arbitrageur
a reply to: Nochzwei
Read his thread on dark matter detection where he explains the work he's doing in that area. I posted a link to it earlier in the thread here.
The link is bust on that thread.
But he/she is barking up the wrong tree. It will fizzle out like the higgs fiasco. Wait and see



posted on Jun, 2 2015 @ 04:31 AM
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originally posted by: Nochzwei

originally posted by: Arbitrageur
a reply to: Nochzwei
Read his thread on dark matter detection where he explains the work he's doing in that area. I posted a link to it earlier in the thread here.
The link is bust on that thread.
But he/she is barking up the wrong tree. It will fizzle out like the higgs fiasco. Wait and see


Fizzle out? As far as i am aware they found what is very likely to be the Higgs and will carry on researching it when the LHC is back up and running soon.



posted on Jun, 2 2015 @ 04:39 AM
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originally posted by: KrzYma

originally posted by: Arbitrageur
a reply to: Parthin
a reply to: Astyanax
Thanks Astyanax, I do have opinions but I'm no expert like ErosA433.

Whether empty space is empty is a loaded question. Our models suggest that even without any regular matter or dark matter, empty space is not really empty because it contains "vacuum energy" which we suspect is probably also what we call "Dark Energy" or at least related to it, and this turns out to be most of the mass/energy content of the universe, maybe 74% according to this:

chandra.harvard.edu...


So even with nothing in it, empty space is not really empty according to quantum field theory.

When you consider the matter we know of, like hydrogen, we suspect the density is something like 1-2 hydrogen atoms per cubic meter in interstellar space. If there's 8 times as much dark matter in other particles, the equivalent of 8-16 hydrogen atoms per cubic meter still seems pretty empty to me, as it's probably better than the best vacuum we can make on Earth. So "empty" is a relative term which is hard to interpret. Scientists get more specific, like stating the number of hydrogen atoms per cubic meter, or the quantity of neutrinos passing through a given area.

Even with all that dark energy filling up the void as we suspect, the mass/energy density of the universe seems low to me because, space is almost inconceivably vast.


WOW, and you guys have measured the whole Universe and came to this conclusion ??
I think your calculations and models are wrong and that is the one and only reason for anything "dark" needed.



Can i ask what your education in the matter is? Do you have a degree in physics or astrophysics? Because if you dont, then what you "think" is irrelevant unless you can back it up with data and maths.

If you are just coming on here and saying thousands of scientists are wrong and lazy with nothing else.....then you are just trolling my friend. Sorry



posted on Jun, 2 2015 @ 06:34 AM
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originally posted by: Nochzwei
The link is bust on that thread.
But he/she is barking up the wrong tree. It will fizzle out like the higgs fiasco. Wait and see

ErosA433 admits there's some chance dark matter may not be detectable directly by any experiment, if it doesn't interact with ordinary matter, and the gravitational effects may be all we can observe. Whether dark matter will be detected in such an experiment is unknown. But if we don't do the experiment, it's certain we won't learn anything. Whether they detect dark matter or get a null result, we will know more than we do now either way.

Try this link:
Direct Dark Matter Detection [A review]

edit on 2-6-2015 by Arbitrageur because: clarification



posted on Jun, 2 2015 @ 01:06 PM
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a reply to: Arbitrageur

There's some significant interpretational consequences.

If dark matter is directly detected, or more correctly a particle interaction is detected which also has the properties necessary to function as astrophysical dark matter, then
a) dark matter is independent dynamical particles
b) you need to add another particle to the zoo.

If dark matter is NOT detected directly, then the possibility remains open that the observations of apparent 'dark matter' or more correctly the interpretation may be flawed and the observations are a consequence of not quite understanding some effect in current physics correctly. Yes I know about the bullet cluster and the observations which appear to be convincing about the reality of dark matter and rejection of previous MOND theory, but there are probably still some holes.

And dark matter could still be dark normal matter too.

Personally I put the odds on dark matter being some real particle, possibly a normal particle, but not SUSY. LHC should have seen SUSY and all her friends by now, but she stood up her date. You think waiting around even longer she still might come?

Dark energy on the other hand, I think could be some kind of unknown basic physics at very large scale.

Notice that both of them come down to very large scale gravitation & metric properties. And we don't have a fully convincing constitutive microscopic generation of gravitation.


edit on 2-6-2015 by mbkennel because: (no reason given)

edit on 2-6-2015 by mbkennel because: (no reason given)



posted on Jun, 2 2015 @ 01:47 PM
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Well said mbkennel, excellent points.


originally posted by: mbkennel
If dark matter is NOT detected directly, then the possibility remains open that the observations of apparent 'dark matter' or more correctly the interpretation may be flawed and the observations are a consequence of not quite understanding some effect in current physics correctly. Yes I know about the bullet cluster and the observations which appear to be convincing about the reality of dark matter and rejection of previous MOND theory, but there are probably still some holes.
I don't think MOND can be completely rejected, but what even some MOND supporters have rejected is that MOND alone could explain observations. The solution could be some MOND-like solution in combination with as yet undiscovered particles.

www.astro.ucla.edu...

Sanders (2002), written by a long time supporter of MOND, recognizes this problem and finds that dark matter is needed in clusters even under MOND.

A long standing problem with MOND was that it did not have a relativistic version. Bekenstein & Sanders (2005) have proposed a solution to this problem. But Zhao et al. (2005) find that this model requires different values for the universal constant ao in different gravitationally lensing clusters of galaxies, so the problem of not having a consistent relativistic version of MOND remains.


It will be frustrating if much of the dark matter is caused by particles even more difficult to detect than neutrinos, because they are already hard to detect.


And dark matter could still be dark normal matter too.
A portion of it certainly is, but I don't know how much. We don't even know the mass of our own Oort cloud in our own solar system and I've seen estimates from 5 Earth masses to 400 Earth masses, and those "guesstimates" are just SWAGs, so the true mass might not even be in that range.

Everybody loves a mystery, and we have one here, well two counting dark matter and dark energy, but dark matter seems more mysterious since some people seem to think they know what dark energy is, sort of.




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