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 expat57
Joined: 2/20/2008
Msg: 1
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Dark Matter and Mathematics ..Page 1 of 9    (1, 2, 3, 4, 5, 6, 7, 8, 9)
First, my very question will show how much I clearly don't know about Dark Matter. I do have questions, though. After reading the thread (fascinating!) on M-Theory and how it all works out mathematically, I now wonder about Dark Matter.

As I've come to understand it:
Dark Matter is more abundant than visible matter.
There is more in Dark Matter than can be mathematically explained.

--The variation in the math seems to conflict with ideas presented in the discussion on M-Theory.
I'm hoping (since so many were so knowledgeable on the subject of M-Theory) .. that some here will be able to offer a layman's version of Dark Matter and it's mathematics.

Also .. any suggested books on the subject that would be understood by a layperson (me)?
 MrGuyCaballero
Joined: 2/27/2007
Msg: 2
Dark Matter and Mathematics ..
Posted: 3/11/2008 10:29:41 PM
Maybe I'm misunderstanding your question, and somebody please correct me if I'm wrong here, but I believe it was a disparity between the amount of observable matter and observations of its behavior that led to the theory of dark matter. In other words, the math didn't work without it.
 JustJanie
Joined: 1/15/2007
Msg: 3
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Dark Matter and Mathematics ..
Posted: 3/14/2008 4:45:36 PM
ExPat57
If you have an interest in dark matter that interest will quickly expand to include dark energy. They are a pair. If you are a newbie, watch anything on the Discovery Channel dealing with these twin phenoms. I had to watch one show about 75 times to get the gist, but once it finally got through to me. Awesome. Have Fun.
 sum1reel
Joined: 6/5/2005
Msg: 4
Dark Matter and Mathematics ..
Posted: 3/14/2008 8:47:13 PM
@ OP


I now wonder about Dark Matter


......dark matter has been theorized to exist only because the notion of it being there fits well into the calculations......it has not been proven to exist!
 2findU
Joined: 11/19/2005
Msg: 5
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Dark Matter and Mathematics ..
Posted: 3/16/2008 2:12:23 PM
Watch "The Universe" on the History Channel. One thing I learned about Dark Matter is that it has been "detected" by its gravitational effects on normal matter. But its a BIG mystery even to astrophysisists.
 cpdemon23
Joined: 3/12/2008
Msg: 6
Dark Matter and Mathematics ..
Posted: 3/16/2008 4:57:18 PM
Scientists in the US have directly observed dark matter according to this

http://today.slac.stanford.edu/feature/darkmatter.asp
 Boomstrike
Joined: 12/1/2007
Msg: 7
Dark Matter and Mathematics ..
Posted: 3/21/2008 7:58:16 PM
Dark energy is what's used to explain why the expansion rate of the universe is increasing. This was a fairly recent discovery which the HST (hubble space telescope) helped to confirm. Nobody really has a very good idea of why this is happening as the discovery was totally unexpected. There is much about the universe that we don't understand. This is one of my favorite websites, a visit to the gallery is the most spiritual experience I have ever had.
http://hubblesite.org/
Click on the hubble discoveries link from the main page or follow this link for a good presentation on dark energy.
http://hubblesite.org/hubble_discoveries/
 expat57
Joined: 2/20/2008
Msg: 8
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Dark Matter and Mathematics ..
Posted: 3/23/2008 11:25:59 AM
Thank you, sincerely for all the comments here.

Boomstrike - what a FIND that site is! I bookmarked it immediately and will find time to explore it at leisure.

ANOTHER QUESTION: It's been my understanding that Dark Matter is the area surrounding what we do know about. Am I wrong on this? I absolutely will do some net searching and see if I can't come up with a book on the topic. It's interested me for some time.
 basher2
Joined: 12/11/2007
Msg: 9
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Dark Matter and Mathematics ..
Posted: 3/25/2008 8:13:11 PM
I'll take a crack at it...
I've done a little reading on this, and one of my professors has published quite a bit on the subject. One of the interesting things in this area is some of the names given to the theoretical particles. There are WIMPS, MACHOS, and WIMPZILLAS to name a few. Awesome.
So, people first started theorizing about dark matter when we started getting good estimates of the amount of luminous matter in distant galaxies. What people found is that they couldn't find anything close to the mass which should be there to cause the galaxies to behave the way they seemed to. It has been estimated that up to 90% of matter would have to be dark matter. There are a lot of theories about what dark matter is, but what I've seen seems to indicate that dark matter is not only not visible, but does not collide with visible matter, or dark matter. It does, however tend to clump in "halos". One area which has contributed to the study of dark matter is the study of ultra high energy cosmic rays (UHECR), which, it is believed, are caused by the annihilation of WIMPZILLAS (I can't remember what it stands for - weakly interacting massive particles sumthin sumthin). There is a major project - I believe in Argentina - which should provide quite a lot of data, which could mean you'll be hearing more about dark matter, or maybe the downfall of the theory of dark matter, soon.
 The Sage
Joined: 4/28/2007
Msg: 10
Dark Matter and Mathematics ..
Posted: 3/29/2008 1:17:25 PM
Satsumo seems to have the best explanation.

It was first hypothesized in the late 1920's or early 1930's. At that time it was felt it was composed of all sorts of masses like dust, faint stars, neutron stars, pulsars, and even energy. Missing mass figures are postulated from harmonic signals.

The only clear evidence of dark matter is distribution of mass in what they call "Bullet Cluster", which results from two colliding galaxy clusters.

Supposedly the hadron accelerator collider will produce energy sufficient to explore dark matter more effectively.
 SpaceSquirrel
Joined: 4/22/2006
Msg: 11
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Dark Matter and Mathematics ..
Posted: 3/30/2008 12:36:48 AM
One of the origins (or at least bits of "supporting evidence") for dark matter is the rotation of galaxies.

We can look at a distant galaxy and get some idea of what all the stars, planets and "normal" (hydrogen, helium, etc) dust/gas weigh. Then we can look at how fast the galaxy rotates. When we plug this info into our models of how gravity works, however, we find that the galaxy is rotating too fast. Things moving that fast should just fly apart rather than continuing rotating about the center of the galaxy. If the galaxy had more mass than we can see, however, then the models would work out. Therefore, we assume there is some form of "dark matter" that we can't "see" in any way except for it's gravitational influence.

There is another possibility. Our understanding of gravity could be incomplete or incorrect. I think this theory is sometimes called "Modified Newtonian Dynamics (MOND for short)". It is less "popular" (and less well developed) than the dark matter hypothesis, but it does exist as an alternative. One version of it has gravity acting as we've understood it for years (special and general relativity) at relatively small distances (say, dozens of light years), but exerting a stronger influence over "galactic" distances of thousands to millions of light years.

Then, as someone mentioned, there is "dark energy". Observations have indicated for years that the universe is expanding. Almost everything is flying away from almost everything else in a manner similar to spots drawn on the surface of a balloon. As the balloon is blown up, it "expands" and all the spots get father apart from each other.

When this expansion was discovered the big question was whether there was enough matter in the universe to eventually stop that expansion and pull everything back together. Everyone assumed that because of how gravity works (or at least the way we think it works) that the expansion should be slowing down because all the mass in the universe gravitationally attracts all the other mass.

Well, a few (like 10-20?) years ago we gathered and analyzed a bunch of observations to try to estimate how much the expansion was slowing down. And we discovered it wasn't ... it was speeding up.

They say there is something called "dark energy" that is "making the expansion of the universe accelerate", but I haven't gotten enough into it to understand quite how they think it does this, but I'm pretty sure there are many different versions.

I think I read that some scientists are investigating the possibility that gravity becomes repulsive at REALLY long (billions of light years) distances, but I'm not sure how seriously they are being taken.

Sorry to ramble so ...
 expat57
Joined: 2/20/2008
Msg: 12
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Dark Matter and Mathematics ..
Posted: 4/6/2008 2:08:23 PM
damn .. ! ..
(I didn't really say that out loud. I only thought it.)

Some smart people in POF. Excellent reading here and I know I will return and read this thread again .. so I can attempt to grasp dark matter. I very, very much appreciate each of you who contributed. Thanks to you.
 abelian
Joined: 1/12/2008
Msg: 13
Dark Matter and Mathematics ..
Posted: 4/10/2008 9:38:43 PM
The bottom line on dark matter is that it's speculative. No experimental search has ever found an event which is a candidate for dark matter. Books written for the lay public on things like M-theory, dark matter, and other novel (and untested) theories generally oversell the significance of the research the author does. If you have enough background, the very latest literature on subjects like dark matter and M-theory may be found in the general relativity and quantum cosmology section of arxiv.org. Also try the section on high energy experiment and astrophysics for the experimental status. Really, this is so controversial that nothing anyone says about dark matter should be taken too seriously.
 abelian
Joined: 1/12/2008
Msg: 14
Dark Matter and Mathematics ..
Posted: 4/10/2008 9:46:34 PM

Scientists in the US have directly observed dark matter according to this

http://today.slac.stanford.edu/feature/darkmatter.asp



That is not a direct observation regardless of how the pr department spins it. A direct observation means having some dark matter pass through a detector here on earth and yielding a signature that was predicted for the type of dark matter in question. What they have is some possible evidence for dark matter. To do better than that, they need to use that data to create a model of the dark matter and predict the behaviour of other similar events (and be correct.)
 abelian
Joined: 1/12/2008
Msg: 15
Dark Matter and Mathematics ..
Posted: 4/10/2008 9:53:19 PM

There was a physicist who postulated that gravity is not a pulling force. His idea was that the universe 'pushes' in all directions at once and that matter (mass) shields other masses from this pushing.


That's called lesage gravity. It's been known to be wrong and unworkable for at least a century and it only lives on in the world of crackpots.
 CountIbli
Joined: 6/1/2005
Msg: 16
Dark Matter and Mathematics ..
Posted: 4/11/2008 12:02:36 AM
I'm quite sceptical about dark matter. It seems like a patch to me -

We have this nice model for how things are, problem is it dosen't actually fit how things are. But we like this model, so rather than admit its wrong, so lets make up some invisble stuff that fixes it.


I couldn't have said it better myself. Here's a simple explanation of dark matter:

http://www.astro.umd.edu/~ssm/mond/flowchart.html

Here's a paper on why dark matter probably doesn't exist:

http://xxx.lanl.gov/abs/astro-ph/0009074
 KaptDan
Joined: 4/2/2008
Msg: 17
Dark Matter and Mathematics ..
Posted: 4/12/2008 6:31:58 PM
I can explain dark matter very simply. And without mathematics. I have a little experiment that anyone can do and you don't need to know Hiller's Theory on Relativity from exactly 100 years ago, Einsteins Special Theory of Relativity, or quantum mechanics or anything at all. Just for this experiment pretend that you know nothing about all of what we know about the cosmos. Even forget about what Galileo theorized. Yes, you heard me right, theorized. Now that your mind is cleared of flawed clutter, go outside if it is DARK outside. Now grab on to something because you will fall down if you equilibrium challenged or you may fall down when you see how simple it is to explain. Now you must read this all and memorize it before you go out because if you don't you will be cheating. Now, once you are outside, look straight up into space. Now as you are looking up, pretend that all the planets, stars, galaxies, airplanes, lightning bugs and everything else is not visible. What do you have left? Once you can understand that what you know already is only someones theory you will realize that you did not waste your time doing this. I am Daniel --(I also invented this "I am Dan" saying before the booby tube people did also.
 veling4
Joined: 10/13/2007
Msg: 18
Dark Matter and Mathematics ..
Posted: 6/21/2008 5:59:07 PM
I want to add that formula which is base for all calculation is wrong, the space and
the time They are not in the same system, one is real other is not,
I still beleave in Eter...
 Vancer
Joined: 10/29/2006
Msg: 19
Dark Matter and Mathematics ..
Posted: 6/21/2008 10:41:41 PM
First humans need to uncover what space is.
Then they'll know.

*flies off into "space"*
 chrono1985
Joined: 11/20/2004
Msg: 20
Dark Matter and Mathematics ..
Posted: 6/21/2008 11:57:20 PM
Dark Matter isn't really a specific type of matter, more a class of matter that we suspect is there but lack any real means of detecting. There's plenty to prove it does exist, but there's also plenty to prove it doesn't.

There's a confusion between Dark Matter and a type of field in space. The field in space is what you more commonly hear explained as Dark Matter, a point in space which gives off no visible elements and lacks the ability to act as a medium for light (hence the confusion).
 OmegaOm
Joined: 4/11/2008
Msg: 21
Dark Matter and Mathematics ..
Posted: 6/22/2008 12:47:19 AM
I personally have never been convinced of the existance of Drak Matter in the enormous quantities that the Dark-Matter thoery predicts. This is science again thinking that all the past succefull thoeries are absolute fact, so they have to invent something radically different and more complex to explain the motion in galaxies. While the idea of the thoery itself is interesting at the very least, I can not understand why it has been researched exclusively as the only explanation of galaxie motion. I am probably being ignorant here, by not knowing all the evidence for dark matter. But why do we not see more other alternatives and explanations for galaxie motion. Maybe there is another weaker force then gravity, that becomes strong at galaxy scales. Maybe gravity doesnt decrease in power by the inverse square at long distances. I have read convincing alternate gravity theories in the astophysics journals, that explain observed galaxie motion. I have read one that has the same elements of the theory Einstien and his partner used in trying to disprove quantum mechanics. Einstein did not like this thoery because it also disagreed with his thoery that nothing moves faster than light. In this thoery, there was a particle that moved instantly. Maybe Einstien and his partner were right, or on the right track.
Anyway I do not like that how science can be close minded, it is suppose to be open-minded. There should be many alternative theories being researched. I only here about Dark Matter. Well good theory, just not enough evidence for me to buy.
 Vancer
Joined: 10/29/2006
Msg: 22
Dark Matter and Mathematics ..
Posted: 6/22/2008 2:17:32 AM
Anyway I do not like that how science can be close minded, it is suppose to be open-minded. There should be many alternative theories being researched. I only here about Dark Matter. Well good theory, just not enough evidence for me to buy.


Unfortunately there are many scientists who are obsessed with the glory received from proving their theories work, rather than proving they don't. Yet it's so much easier to find proof that something doesn't work, rather than the relentless pursuit of figuring out how to make it work.
It's a ****ing hypocritical waste of resources.

There are also many though who are open-minded and willing to accept they are wasting time and will pursue a completely different approach. Demonstrations of brilliance and humility will often push those few into the limelight and over time the community gains more trust in their opinion.
 abelian
Joined: 1/12/2008
Msg: 23
Dark Matter and Mathematics ..
Posted: 6/22/2008 3:22:40 PM

First, my very question will show how much I clearly don't know about Dark Matter. I do have questions, though. After reading the thread (fascinating!) on M-Theory and how it all works out mathematically, I now wonder about Dark Matter.


Whether or not M-theory works out mathematically such that our universe is one of the possibilities, is an open question.


Dark Matter is more abundant than visible matter.
There is more in Dark Matter than can be mathematically explained.


Neither of those statements is necessarily accurate. The idea of dark matter originates in several ways, but it's existence has never been confirmed by an experiment. The idea that it's more abundant than visible matter is due to observations of galactic rotation. The galactic rotation curves do not appear to be explicable from the gravitational effects of visible matter, so much so that the dark matter must be very abundant. Apparently, it's possible to assume a lot of dark matter in a way that doesn't conflict with anything else general relativity predicts and which has been experimentally verified. That doesn't meen dark matter is necessary or general relativity is ultimately correct. It just means everything is self-consistent and gives us something to check out.

There can't be more dark matter than mathematics can explain, since presumably the uiverse obeys some physical laws. There can be too much (or too little) dark matter than a particular theory can explain because mathematics constrains the concrete predictions a theory can make and still be viable. Right now though, it's safe to say that there is not more dark matter than anything can explain since no one has any hard evidence that dark matter exists.



I'm hoping (since so many were so knowledgeable on the subject of M-Theory) .. that some here will be able to offer a layman's version of Dark Matter and it's mathematics.


First of all, there are many different kinds of dark matter that have been postulated, so there is no generic dark matter. Each type originates from a line of reasoning beyond existing theories and so are not necessarily easy to understand. Search google for "dark matter" and "galactic rotation curves."
Since general relativity doesn't care about the type of dark matter that is responsible for the gravitational field, this applies accross the board.

Particular species of dark matter arising in the context of high energy physics are things called Weakly Interacting Massive Particles (WIMPS), MAssive Compact Halo Objects (MACHOS), and more exotic items like sterile neutrinos. The latter has some theoretical merit, but for that reason, you'll find it difficult to understand without knowing something about weak decays.

Also .. any suggested books on the subject that would be understood by a layperson (me)?

You got me on that one. The only books I have that go near M-theory are lecture notes that were bound and sold as a two volume set and I have a lot of trouble understanding what's in those books.
It's a very technical and complex subject.

You might look for something written by Ed Witten. He's one of the leading proponents of M-theory and although he's capable of writing things no one else understands, he also writes well in articles aimed at mortals.
 ZeroSpazz
Joined: 1/31/2008
Msg: 24
Dark Matter and Mathematics ..
Posted: 6/22/2008 3:35:27 PM
The best estimates now say that the Universe is made of 4% regular baryonic matter, 23% dark matter and 73% dark energy.
Given that the 4% is what we know though observation and that observation itself as well as the shape, speed and orientation of that is still not clearly understood or even a known fact, one would have to estimate that there is a .00325% chance that big bang is correct.
From where I stand the world is flat and I am the center of the universe.
 abelian
Joined: 1/12/2008
Msg: 25
Dark Matter and Mathematics ..
Posted: 6/22/2008 3:38:41 PM

Anyway I do not like that how science can be close minded, it is suppose to be open-minded. There should be many alternative theories being researched.


Science is open minded. If you have an alternative theory which actually explains everything we already know and predicts something new that can be tested, your theory will be welcomed. Scientists are not interested in alternatives that have already been ruled out by observations. Those were only alternatives before being ruled out. There is not much point in considering a theory which is known to fail the ``agrees with reality'' test as an alternative.

I only here about Dark Matter. Well good theory, just not enough evidence for me to buy.


Aren't you being a bt hypocritical? Before you decide you don't ``buy'' it, shouldn't you first have a detailed understanding of what you aren't ``buying?'' I mean, I know a fair amount about this subject at a level that I can read and understand the literature and I find a lot of the motivation for dark matter a little suspect, but that doesn't mean it can't really be the reason behind the motivation. It's not an unreasonable idea, it's supported by observation even if it isn't through direct evidence and it doesn't contradict any other observations or experimental data. Despite whatever suspiscion I might have, neither I nor anyone else has come up with an alternative which has as much going for it, however little that might be. Propose a better alternative and bored physicists everywhere will be happy to listen.
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