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Author Topic: What is dark matter and what is its effect on matter?  (Read 3323 times)

Offline thuggery

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Please be gentle with me, i am a virgin at this and i am no were near a scientist. i have just watched a vid on youtube called Dark secrets what science tells us about the hidden universe, made by peeps at berkley uni. This a quote from the scientist alexie Leauthaud. If you throw dark matter at normal matter it has no effect it just passes through, Please tell me how she came to this assumption because since no none knows how to see touch experience it in anyway. Is this scientist just waffling lol. (no disrespect intended)
« Last Edit: 04/10/2012 16:12:17 by chris »


 

Offline graham.d

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Re: Dark energy and the assumptions scientists make
« Reply #1 on: 28/09/2012 16:29:03 »
Making observations of galaxies has shown that the speed that the stars are moving in their rotation around the galactic centre of mass is not as would be expected. The speeds are not what would be predicted as a function of their distance from the galactic centre. The prediction is based on a fundamental relationship between the total kinetic energy and the total potential energy in a closed system known as the Virial theorem.

The simplest explanation for this, that does not involve our whole understanding of physics, is that the stars are obeying the Virial Theorem but that there is much more matter there than we are observing. People have constructed computer models of how such unobserved matter (dark matter) should be distributed to result in the observed data and the results show quite a good fit when the matter is distributed in a sphere surrounding the galaxy.

Stars and galaxies form by accretion of matter. This accretion occurs as a result of mutual attraction and by the loss of energy resulting when matter interacts (i.e. collides). Because all the colliding matter rarely forms with no net angular momentum the net result is frequently the disk shape we are familiar with. For gravitating matter to form into and remain as a spherical cloud it would mean that it must be in continuous multiple orbits that do not lose energy (or at least very little energy) by interaction with conventional matter or even with itself. Logically, this model leads to these conclusions.

Of course all this is based on modelling and we have not got any dark matter to play with and examine. However, it does seem a simple conceptual explanation and probably the best we have to date. Other explanations that rely on changing the laws of physics as we understand them seem more unlikely.

One thing to note is that this is what is referred to as Dark Matter. Dark Energy is something else entirely and to do with trying to explain the changing of the rate of the expansion of the universe.
 

Offline yor_on

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Re: What is dark matter and what is its effect on matter?
« Reply #2 on: 04/10/2012 16:47:59 »
Have no idea what she means actually? Although it may be that she's associating it to neutrinos in some manner? We've never seen any 'dark matter' but we presume it to exist, just for the reasons Graham wrote. It depends on its distribution, if you assume a even distribution through the universe she might be right? I don't really know, it's highly theoretical.
 

Offline distimpson

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Re: What is dark matter and what is its effect on matter?
« Reply #3 on: 24/10/2012 04:52:30 »
Hello Thuggery, I finally got a chance to watch the video you wrote about, I believe this is the link http://www.youtube.com/watch?v=YezKsgsPM24. Good presentation, thank you, wouldn't have know about it otherwise.

I'll take a crack at  your question too. Dr. Alexie Leauthaud was speaking to a question from the audience, is dark matter anti-matter? Her answer was "no" because we would see some interaction between anti-matter and normal matter (in addition to gravitational effects). Her example of the bullet cluster described the interaction between the colliding galaxy clusters, in the picture below one is moving to the left, the other to the right. It appears the two groups of galaxies passed right through each other (substantially) and left their associated hot gas clouds behind in the center of the collision (colored red). In addition, gravitational lensing suggests there is a lot more mass than we can see and it is located in two lobes in the same regions as the galaxy groups (colored blue). So, if the gravitational lensing is due to dark matter and the dm regions traveled along with the two galaxy groups then they too appear to have passed right through each other and the hot gas clouds with no noticeable effect. Speculation or hypothesis, some physicists think there are yet-to-be discovered dm particles lurking about. Since detectors are typically made of normal matter, detection may be challenging.  My best effort to understand this.

 

Offline Cgha2173

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Re: What is dark matter and what is its effect on matter?
« Reply #4 on: 12/12/2014 08:17:27 »
When one contemplates the greater mysteries of the cosmos, I think one must be prepared to think outside the box...

Our current methods of science gain complexity, scope, and information exponentially over time. It is simply amazing to consider the depth of human understanding in the 21st century. Particularly, the last few decades has seen the emergence of String Theory, which in itself, seems to be slowly reconciling anomolies in quantum mechanics, leading to the primordial building blocks of what we now call, M-Theory. Einstein was not subtle in his quest for a unifying theory of the 4 forces established in the universe (Electio-magnetic, Gravitational, Strong, and Weak nuclear).
M-Theory seems to be the beginning of what could potentially be our realisation of Einstein's dream.

My reply is not to bore you with details, nor implications of the mentioned theories, but instead to highlight one particular mystery of the universe, one that our science has no seemingly possible way to detect - I am speaking of 'dark matter'. Again, instead of detailing its 'known' properties (which at this stage, is next to nothing), I am proposing a rather unusual conclusion. Now, before I begin to be labelled a 'crack-pot lunatic', or some proponent of the 'New Age hippie' movement, remember we are attempting to explain notions that are beyond our grasp, at least for now.

So, I now return to the 4 Forces. Could it be that dark matter is, in fact, a fifth force in our universe (as opposed to thinking of it as 'matter' per say, but rather, a force of energy, such as EM). This, of course, is not a new idea. However, in and of itself, this idea is nothing more than that. An idea. If it is the 5th Force, then why can't we detect it? We have solved nothing. Seemingly, all this idea really is, is substituting one unknown with another, without any real science.

We are missing 'something'. Something crucial. Something that explains all. My proposition - Consciousness.

Consciousness is the word I am using, but be wary not to confuse this with our own subjective experience of what we think of consciousness as. I've heard many say, "we cannot tie physics and metaphysics together, unless the universe itself is alive, and aware...etc". Who's to say the universe isn't a conscious organism? The definition of an organism is "any complex thing or system having properties and functions determined not only by the properties and relations of its individual parts, but by the character of the whole that they compose and by the relations of the parts to the whole." Now, let us leave that for now. My point, is merely to illustrate that when discussing these matters, one cannot rule out much, with certainty.

Now, imagine universal consciousness as just another force in the universe. In theory, it should be all around us at all times. In theory, not only people and animals would have consciousness, but trees, dirt, even stars and planets, would too have consciousness (again, not necessarily in the way we think of this term). Generally, physics can explain chemistry, and chemistry will explain biology. When biological entities develop extremely complex brains, this is when, and only when, consciousness can be 'measured', or even made aware entirely. This is the subjective experience. This is our reality. It is important to note that while a jellyfish may not seem to have consciousness to 'us' (a conscious observer), in reality, we could have no possible idea - scientifically speaking.

Why consciousness? Without getting too spiritual, and also attempting not to mention the word 'God', it is quite clear, at least to me, that there must be a 'creative, and aware force' - universal consciousness. Despite science's best attempts of bridging the gap from inanimate to animate, from nothing to something, or for genetic 'information' (DNA) to exist at all (of course, I understand this is almost considered blasphemy in many mainstream scientific circles), there is clearly 'something' missing. The reason I speak of the possible significance that the role of consciousness plays in our universe (many physicists since Einstein have been bemused and perplexed at experiments whose results seem to influenced by the conscious observer), is simply to propose that not only has it an important role to play in the universe, but is in fact intrinsically linked to the very foundations from the Big Bang, just like the other 4 forces.

Could there be a '5th' force in the universe? Could this fifth force actually be 'dark matter'? Could the reason why our science cannot sufficiently detect either of these notions be due to the fact we have almost 0 understanding of consciousness?

Food for thought...     
 

Offline evan_au

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Re: What is dark matter and what is its effect on matter?
« Reply #5 on: 12/12/2014 09:57:54 »
There have been many theories about the composition of dark matter. Many of these theories have been ruled out by additional observations. Most physicists now think that Dark Matter is composed of some subatomic particle that does not interact with our familiar matter.

We know of some subatomic particles like neutrinos which pass through matter without interacting very much at all - but astronomical observations suggest that neutrinos can't be responsible for all the dark matter.

Current theories of subatomic particles suggest that there may be other particles (eg one dubbed an "axion") which interact with matter even less than neutrinos. Given the great difficulty of detecting neutrinos, these hypothetical particles would be very extremely hard to detect - but there are scientists around the world who are still trying (after all, there is a Nobel Prize waiting for the discoverer of Dark Matter). So far, there are no verified sightings.
« Last Edit: 12/12/2014 23:56:45 by evan_au »
 

Offline PmbPhy

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Re: What is dark matter and what is its effect on matter?
« Reply #6 on: 12/12/2014 13:45:37 »
Quote from: thuggery
Please be gentle with me, i am a virgin at this and i am no were near a scientist. i have just watched a vid on youtube called Dark secrets what science tells us about the hidden universe, made by peeps at berkley uni. This a quote from the scientist alexie Leauthaud. If you throw dark matter at normal matter it has no effect it just passes through, Please tell me how she came to this assumption because since no none knows how to see touch experience it in anyway. Is this scientist just waffling lol. (no disrespect intended)
Dark matter is the matter which is postulated to be present in galaxies which causes the rotation curves to be different than expected by theory.

That person doesn't know what they're talking about on that point. Dark matter is simply matter which doesn't reflect light because it doesn't interact with charged particles due to their charge. That doesn't mean that it doesn't interact with the strong force and it doesn't mean that it doesn't interact with gravity. One type of dark matter postulated are tiny black holes. There's no way that normal mater will pass right through it. Being so small they're hard to detect though.

See http://www.space.com/23583-dark-matter-tiny-black-holes.html
« Last Edit: 12/12/2014 13:50:22 by PmbPhy »
 

Offline Ethos_

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Re: What is dark matter and what is its effect on matter?
« Reply #7 on: 12/12/2014 20:33:55 »

I was just reading this article today and thought it might fit into this thread quite nicely.............enjoy!

http://news.yahoo.com/cosmic-mystery-solved-possible-dark-matter-signal-spotted-124020784.html
 

Offline JohnDuffield

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Re: What is dark matter and what is its effect on matter?
« Reply #8 on: 12/12/2014 22:01:33 »
Please be gentle with me, i am a virgin at this and i am no were near a scientist. i have just watched a vid on youtube called Dark secrets what science tells us about the hidden universe, made by peeps at berkley uni. This a quote from the scientist alexie Leauthaud. If you throw dark matter at normal matter it has no effect it just passes through, Please tell me how she came to this assumption because since no none knows how to see touch experience it in anyway. Is this scientist just waffling lol. (no disrespect intended)
Yes.

We know from galactic rotation curves and other evidence that there's something out there causing more gravity than we expect. We call it dark matter, but we don't actually know what it is. The "dark" bit is reasonable enough, because we canít see it. But the "matter" bit isn't. Take a look at the Foundation of the General Theory of Relativity where Einstein said "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". It's energy that causes gravity, not matter per se. Matter only causes gravity because matter contains energy. So it's wrong to assume that some kind of matter particles are the cause of gravitational anomalies. See http://arxiv.org/abs/1209.0563 and note this: space has its vacuum energy, this has a mass equivalence, and space, of course, is dark.   
« Last Edit: 12/12/2014 22:03:33 by JohnDuffield »
 

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Re: What is dark matter and what is its effect on matter?
« Reply #8 on: 12/12/2014 22:01:33 »

 

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