on the origin of dark matter...

[bwanaaa]

My understanding is that the first bits of data came from Vera Rubin who found that the rotational velocity of a galaxy did not adhere to newtonian law...the rim was spinning a lot faster than it should. From this, dark matter was inferred. Stuff that adds to gravity but can't be detected otherwise,



If this were the case then light traveling through dark matter should be blueshifted. I thought gravitational redshift was demonstrated first was proven by the Pound-Rebka experiment. So dark matter seems a contradiction to that data.

I wonder though what the effect of increased velocity is on mass? Is it not true that mass increases as one approaches lightspeed? Can the orbital velocity of stars themselves account for increased gravity? It's a question of numbers actually and one has to have a handle on the actual data-which I dont. So I ask here.

 

[ModestGamer]

My understanding is that the first bits of data came from Vera Rubin who found that the rotational velocity of a galaxy did not adhere to newtonian law...the rim was spinning a lot faster than it should. From this, dark matter was inferred. Stuff that adds to gravity but can't be detected otherwise,



If this were the case then light traveling through dark matter should be blueshifted. I thought gravitational redshift was demonstrated first was proven by the Pound-Rebka experiment. So dark matter seems a contradiction to that data.

I wonder though what the effect of increased velocity is on mass? Is it not true that mass increases as one approaches lightspeed? Can the orbital velocity of stars themselves account for increased gravity? It's a question of numbers actually and one has to have a handle on the actual data-which I dont. So I ask here.

or they just have no idea WTF they are talking about.

everybody should start turning these on. Wouldn't just be easier to say. I don't know.

If you wish to participate in Highly Technical, then you need to be able to make technical arguments. Posts like this will not fly here.
-ViRGE

 

[Pulsar]

or they just have no idea WTF they are talking about.

everybody should start turning these on. Wouldn't just be easier to say. I don't know.

Stay a gamer, because you don't know what you're talking about.

When they realized that things weren't acting the way they should, they knew something was influencing them. So they called it dark matter. "dark" is a fairly common designation when scientists don't understand something.

So, in effect, they are admitting they don't know anything about it, but they know something is there.

I suppose you'd rather them say "the invisible influence that is skewing our test results" rather than just calling it "dark matter". Sheesh.

 

[Daedalus685]

My understanding is that the first bits of data came from Vera Rubin who found that the rotational velocity of a galaxy did not adhere to newtonian law...the rim was spinning a lot faster than it should. From this, dark matter was inferred. Stuff that adds to gravity but can't be detected otherwise,



If this were the case then light traveling through dark matter should be blueshifted. I thought gravitational redshift was demonstrated first was proven by the Pound-Rebka experiment. So dark matter seems a contradiction to that data.

I wonder though what the effect of increased velocity is on mass? Is it not true that mass increases as one approaches lightspeed? Can the orbital velocity of stars themselves account for increased gravity? It's a question of numbers actually and one has to have a handle on the actual data-which I dont. So I ask here.

Celestial blue/red shift is very negligibly due to gravitational effects. It has been shown terrestrially but is far too small of an effect to be seen here and actually separate from those due to movement.

Gravitational lensing is a better bet to find a clump of the stuff but it seems it is rather evenly spread out.

Gravitational red/blue shift would be effected by everything in the path, even if light traveled through a cloud of dark matter if would only be blueshifting on the way there, and redshifting once it passes it. Because of the fall of of gravitational fields only in a case where the cloud was extremely close to us would we be able to notice the blue shift as in other cases it would cancel out to well within our ability to measure it.

The reason we assume it is dark matter is that the steady velocity curve is perfectly explained by large amounts of mass outside of the galaxy. Since we know there should be more mass in the universe than we observe it made sense to assume it was simply not detectable (at least not easily) but there. The other explanations involve altering the current theories of gravitation which could certainly be the case (such as the MOG theory). When one says dark matter they often mean either or. Dark matter as mass we don't see is more accepted for obvious reasons but theories do exist that can explain the curves without it.

The fact is that by most of our physics there is too little mass/energy about for a stable universe. It makes sense to assume this mass is causing something that we notice needs more mass to explain.


As far as orbital velocities explaining the extra mass goes... Nothing is even close to relativistic speeds here, and it simply doesn't work that way even if they were. More often than not when one says teh mass is increasing they simply mean that the product of gamma and rest mass is now larger than rest mass itself.

 

[ModestGamer]

How about this.

the math is flawed and they can't admit it. So instead they come up with crazy exoctic explinations.

Stay a gamer, because you don't know what you're talking about.

When they realized that things weren't acting the way they should, they knew something was influencing them. So they called it dark matter. "dark" is a fairly common designation when scientists don't understand something.

So, in effect, they are admitting they don't know anything about it, but they know something is there.

I suppose you'd rather them say "the invisible influence that is skewing our test results" rather than just calling it "dark matter". Sheesh.

 

[bwanaaa]

Celestial blue/red shift is very negligibly due to gravitational effects. .....

I guess that's the nut of the problem. If we postulate dark matter in such large quantities to alter orbital dynamics at the edge of galaxies, then why dont we see the effect on light coming from very far away galaxies(where there is less dark matter)?? If we lived in a giant puddle of dark matter, light should be blue shifted much more than it is when it reaches our eyes.

If you try to say that dark matter is everywhere and therefore there is no differential effect on light, then you come back to the problem of explaining the aberrant orbital velocity at the edge of the galaxy as compared to the middle-dark matter everywhere would cancel out differential gravitic effects.

One way to get around this is to say dark matter gravity affects mass but not light. Regular matter gravity would have to affect mass and light.

 

[TastesLikeChicken]

I guess that's the nut of the problem. If we postulate dark matter in such large quantities to alter orbital dynamics at the edge of galaxies, then why dont we see the effect on light coming from very far away galaxies(where there is less dark matter)?? If we lived in a giant puddle of dark matter, light should be blue shifted much more than it is when it reaches our eyes.

If you try to say that dark matter is everywhere and therefore there is no differential effect on light, then you come back to the problem of explaining the aberrant orbital velocity at the edge of the galaxy as compared to the middle-dark matter everywhere would cancel out differential gravitic effects.

One way to get around this is to say dark matter gravity affects mass but not light. Regular matter gravity would have to affect mass and light.

One problem with that. If dark matter didn't affect light it brings up the question of what creates gravitational lensing when no visible mass is observed to cause it?

 

[ModestGamer]

http://www.universetoday.com/2010/03/24/astronomers-find-90-more-universe/

Look that missing 90% of the universe "dark matter " has been found.

Oh the irony of this thread.

This guy is spot on.

We Should Dismiss “Dark matter” and M-Theory.
Written by P.Martone
For decades Science has been unable to accurately explain where 90% of the mass in the Universe is. Cosmologists and Theoretical Quantum Physicists have developed one elaborate theory after another to compensate for this “missing” mass. With a simple change in how we observe the Universe it has been revealed that for decades we simply did not perceive 90% of the energy emitted by these “missing Galaxies, gas and dust clouds” with mass that “Dark Matter” and “M-Theory” (A function of String Theory) were substitutes for. With these “missing” Galaxies, gas and dust clouds now observable, we can lay down complex, abstract and incorrect theories that fail to accurately model the Mechanical Universe.
This underscores a fundamental flaw in Physics. The flaw is a lack of understanding of how and why gravity works. Gravity as a force has been identified, measurements made and accurate predictions of its effect(s) have been developed. Because of this we keep making a fundamental mistake that has ramifications in Science and Academia. We allow side stepping of the fact that we do not have a full and complete understanding of gravity and why it works and emphasize only that it works, allowing Scientists to postulate one wrong theory after the other and incorporate them into our collective (mis)understanding of the Universe.

Mind you the telescope observations didn't say the area of the universe was 90% larger. but that it had 90% more matter in it then previsouly seen.IE the universe has a much higher then previously accepted density.

 

[TastesLikeChicken]

http://www.universetoday.com/2010/03/24/astronomers-find-90-more-universe/

Look that missing 90% of the universe "dark matter " has been found.

Oh the irony of this thread.

This guy is spot on.



Mind you the telescope observations didn't say the area of the universe was 90% larger. but that it had 90% more matter in it then previsouly seen.IE the universe has a much higher then previously accepted density.

Read the article more closely next time. It actually tells you that up to 90% of visible galaxies have previously gone unobserved, a problem astronomers already were aware of to a certain extent. Now more are able to be detected. It's a solution for a known problem. This article has nothing to do with dark matter at all.

Nice job sailing the failboat over the edge of the world though.

 

[ModestGamer]

Read the article more closely next time. It actually tells you that up to 90% of visible galaxies have previously gone unobserved, a problem astronomers already were aware of to a certain extent. Now more are able to be detected. It's a solution for a known problem. This article has nothing to do with dark matter at all.

Nice job sailing the failboat over the edge of the world though.

Science is becoming a religion sadly.Already aware of the problem. If they missed by 90% whose to say that they only ever saw 1%.

Lets face it. exoctic solutions to problems are rarely ever a good solution.

science could use a bit of a great old engineering exspression.

K.I.S.S.

I am not the one sialing the fialboat BTW.

Also thanx for again making my point about assuming.

They assumed something was there without tangiable proof.

It is becoming a ever greater problem.

did you find out why light travels in a wave ?

 

[Daedalus685]

Modest... do you know what dark matter is?

It is simply a construct for mass we cannot see. Galaxies we missed, dust clouds of too low temperature to radiate enough energy, gas clouds away from stars.. These are all dark matter. That is what dark matter is... Dark matter is not something magical or mystical.. it is simply regular old matter that for one reason or another we have been unable to directly observe. When an astrophysicist discovers a huge chunk of mass that we couldn't see before this is not discounting dark matter.. it is dark matter.

There are still assumptions that some dark matter must be exotic particles as it is more difficult to see than it 'should be'... but the vast majority of it is simply dust no more special than what orbits the sun in the kupier belt or ort cloud. Dark energy is something else entirely and is simply a word to describe the source of the universal expansion that as of yet is unexplained.


Back to blue and red shift to address some more of what bwanaaa was asking:

'Dark matter' is assumed to exist in an evenly dispersed spherical like cloud around the galaxies. Lets assume that this is the case and we are watching a well understood super nova from an average distant galaxy.

This dark matter cloud will blue shift the light as it approaches its centre of mass. If we assume it is a homogeneous could this centre of mass would be in the middle of the galaxy and the light would be blue shifted on the entire way here. Now, this blue shift woudl be VERY small compared to the redshift the expansion of the universe and recession of the galaxy causes.

So, assuming we know the spectrum of the supernova perfectly the contribution to the redshift from gravitational effects cold be known if we know the distance to the galaxy exactly. The problem is the farther out we get the less we know about the distance. In fact, for distant objects most of what we know about the distance is due to the red shift itself. The result is that the error in our measurement is well larger than the contribution to the gravitational redshift is, even including regular matter.

Even if 80% of the mass of the galaxy is dark matter we still have an even lower chance of detecting it. It is simply too difficult to measure cosmologically as its effects are too small. We can only measure it on earth by using the earths gravity and frequency sources we know to the hundreds of decimal places. For cosmology 5% uncertainty is acceptable which simply is not good enough... maybe one day.

Dark matter may end up not being very special.. though it is assumed that it is at least mainly composed of weakly interacting particles. I find it concerning that modest actually beleives that the science is flawed.. though I assume he simply does not understand what it is about.

 

[Daedalus685]

Science is becoming a religion sadly.Already aware of the problem. If they missed by 90% whose to say that they only ever saw 1%.

We know to a good approximation how massive the universe should be based on the FLRW metric(general relativity) which predicts the energy/mass/vacuum energy contributions required to result in a stable universe like the one we observe.

We also know that we have not observed nearly enough of this matter... Thus we call everything else dark matter.

They assumed something was there without tangiable proof.

They assumed nothing. There is not enough observable mass so they call it dark matter to avoid assuming what it is. There are likely clouds of non baryonic matter out there, but we don't know for sure what they woudl be made up of.. there is a large host of particles they could be. Since we don't know we call it dark matter to include all of the possibilities... Including that general relativity is slightly wrong (incomplete) on some scales.

did you find out why light travels in a wave ?

Light is a wave because ALL particles behaves like a wave. Even you behave as a wave but because we are rather massive objects our wavelength is exceedingly small. It is not a wave like you seem to understand as it is quantized. It is both a wave and a particle and our ability to observe behaviour of either is dependant on the amount of energy in question. This is a fundamental tenant of quantum mechanics.

 

[bwanaaa]

tnx daedalus for your explanation of the comparison of the relative magnitudes of gravitational redshift and dark matter blue shift. Now you have picqued my interest and I would like to ask 'please show me the data'. But perhaps I should remember the ancient Chinese curse 'beware what you wish for as you may not like the answer'.

 

[bwanaaa]

@modestgamer
please dont take this the wrong way, but I urge you to seek evaluation. Your patterns of thought, repeated misspellings, and disconnected sentences make me concerned about the possibility of an underlying disorder. Your posts in multiple forums have the same disjointed quality. Unhappiness is leaking out of every sentence. Indeed, many of your comments have merit, but they are not clarifying comments, rather they are confusing. You might significantly improve the quality of your life with a simple pill. Although you are obviously functional and probably also employed, you could make your world and that of those around you better.

 

[Daedalus685]

For instance we can look directly at the equations of gravitational and Doppler red shift.

For a relatively close (cosmologically speaking) galaxy recession from us would be on the order of 10000km/s. Lets make that 5000km/s so we are talking very close (as in local cluster) galaxies. Assume the motion is in the line of site only.

Using the equation:

z = ((1+v/c0)/(1-v/c))^1/2 we get 0.017 as the value of z. We can simply use v/c as v is low enough. This represents 1/10 of the z value to be classified as large z. We might see much smaller values closer to us, the CMB is z=1800 or so.

Now, for gravitational redshifting:

z = 1/(1-(2GM/rc^2))^1/2 Using the mass of our galaxy (5.8e11 Msun), distance to galactic core of 26000LY, and the correct constants (and units) the result is z = .000003

Measuring the redshift to .002 is considered great for a distant supernova. We know Andromeda's to an error of about +/- .00001 and it is -.001 (blueshift).

Even the best measurements we have are an order of magnitude above the maximum gravitational redshift.. This is even if we assume the entire galaxy is dark matter. The effect is simply far too small to notice. And the contribution from Doppler and space time expansion becomes massive at larger distances. Add to that that we would have to wait for sufficient supernovae.

There are some papers on cosmologically observed gravitational redshift but these are all from within the galaxy so dark matter does not apply. It only really works if you are very close to a huge object that is VERY well understood. Such as the earth and are imaging photons emitted from nearly perfect lasers.

 

[DrPizza]

Dark matter is NOT dust. This would be detectable by absorption spectra, black body radiation, etc.

Do you know what weakly interacting means? Regular matter, the stuff we're familiar with, is not weakly interacting. You can't have both of those things in one answer.

Also, gravitational lensing effects HAVE been observed & provide evidence of the existence of dark matter. We just don't know what dark matter is. But, we DO know what it isn't. It isn't made up of things like protons and neutrons and electrons.

There's plenty of understandable material here:
http://en.wikipedia.org/wiki/Dark_matter

 

[bwanaaa]

the wikipedia is amazing...if only it existed when i was in high school...can you imagine i found a map of dark matter based on weak gravitational lensing

http://en.wikipedia.org/wiki/File:COSMOS_3D_dark_matter_map.jpg

And the whole idea of modified newtonian gravitics as an alternative theory is also lucidly presented. That a guy named Zwicky thought this up in the 30s but was largely ignored for a long time is interesting. Obviously, he had to have a real job and it seems developing jet engines during ww2 was the JOB that earned him professional respect. I imagine his fanciful dark matter idea was tolerated by his peers and colleagues a quaint eccentricity. That plus the fact that he appears to have been a cheerful sort.

 

[William Gaatjes]

I bet stretched wavelengths...

Seek strong sources of gravity. There you will find your dark matter.
Stretching of the space - time aether is all you need to conceal.
Dark matter is not missing, dark matter is simply not interacting. But it is still there...

 

[ModestGamer]

@modestgamer
please dont take this the wrong way, but I urge you to seek evaluation. Your patterns of thought, repeated misspellings, and disconnected sentences make me concerned about the possibility of an underlying disorder. Your posts in multiple forums have the same disjointed quality. Unhappiness is leaking out of every sentence. Indeed, many of your comments have merit, but they are not clarifying comments, rather they are confusing. You might significantly improve the quality of your life with a simple pill. Although you are obviously functional and probably also employed, you could make your world and that of those around you better.

I am not attempting to answer questions. I don't know. I do like pointing out the

GLARING FLAWS IN THE MATH

becuase ultimately we ASSUME to much.

Get used to it. some people are just grumpy. I am one of them

No I don't want any pills.

Get used to confusion. Man is just about smarter then monkeys and not by much. Shit most of the time we are completely unaware of our own behavior.

Whats truthfully annoying.

Dark matter doesn't exist.The flaw is in our calculation of the effects of a force that we don't understand.

Gravity.

We don't know how it works so,they imply exoctic nature as the new standard in physics.

Its really very lame.

Its just like the MASSIVE flaw with relativity.

Why would time dilation occur ? the error is human percpetion. The answer is time does not exist.

Now if you want to say that gravity may influence the rate at which matter interacts and or changes state that is truthful and measrueable. But that only works if gravity interferes.

Without gravity what else would cuase a relative change in velocity ?

Back to that thing abotu constants.

There are no universal constants. It makes humans feel better about the universe but the speed of light is just that. The speed of light. Now how the speed of light is a behavior of photons vs atoms and how matter interacts as we observe it with layer os complexity above and below the level of photons. the speed of light may have a boundary area that is typical. There may be some cosmilogical truth in the speed of light IE particales of a given size may only travel at X velocity. . However it is not a constant. Simply a state of existance.

Its not that I don't "Get" the physics. Its that I think alot of it is bullshit and I don't mind saying so.

Hence the underlying socialogical issue with humans.

We assume to much and solid numbers make us feel better.

BTW I know I am wired differently and its ok with me. I can do complex 3d modeling in my mind eye and all sorts of virtual tasks.

I can build complete circuts or engines or 3d objects and look at grain structures as if they were right in my hands. I also can do nonlinear thought and can abstract as well as do projection and 3dimensional charting with near pinpoint accuracy. All without a pen or paper. I can crunch numbers to minute decimal places.

I can take any object I may have assembled and disasembled and blow it apart into a 3d rendering as if it were a cad cam drawing. I can also compose music in my had and translate it directly to paper. I can also recal every piece of music I have ever heard in my life with crystal clarity as if it was played aloud for the world to hear.



but I admit. trying to get out what I can easily comprehend in english. Not always so easy. Not only that It comes with a heavy penalty in terms of social skills. I do get along however.

but the blessing is also a curse.

 

[TastesLikeChicken]

I am not attempting to answer questions. I don't know. I do like pointing out the

GLARING FLAWS IN THE MATH

You haven't shown the first bit of math that overturns existing theory.

Whats truthfully annoying.

Dark matter doesn't exist.The flaw is in our calculation of the effects of a force that we don't understand.

We have already known one form of dark matter for many years - neutrinos. They are a weakly interacting form of matter and are non-baryonic, which is what nearly all forms of dark matter are proposed to be. The fact that we have not identified all other forms of dark matter yet is meaningless. There is a decent amount of evidence that it exists.

Gravity.

We don't know how it works so,they imply exoctic nature as the new standard in physics.

You confuse knowing vs. explaining. Science doesn't know. Science explains. That is the best humans can ever do. We can never know anything with absolute certainty because truly knowing is ultimately arbitrary. We can only "know" within human contraints. However, that doesn't make our explanations wrong. Scientific explanations are merely our interpretation of knowing.

snip

Calling bs is not enough in this place if you want to overturn existing theory. If the math is wrong, show the right math. If the current theory of gravity is wrong then explain a viable alternative. iow, nobody gives a crap that your personal opinion is that science is wrong. Prove it with facts or stop wasting the bandwidth.

 

[William Gaatjes]

I am not attempting to answer questions. I don't know. I do like pointing out the

GLARING FLAWS IN THE MATH

becuase ultimately we ASSUME to much.

Get used to it. some people are just grumpy. I am one of them

No I don't want any pills.

Get used to confusion. Man is just about smarter then monkeys and not by much. Shit most of the time we are completely unaware of our own behavior.

Whats truthfully annoying.

Dark matter doesn't exist.The flaw is in our calculation of the effects of a force that we don't understand.

Gravity.

We don't know how it works so,they imply exoctic nature as the new standard in physics.

Its really very lame.

Its just like the MASSIVE flaw with relativity.

Why would time dilation occur ? the error is human percpetion. The answer is time does not exist.

Now if you want to say that gravity may influence the rate at which matter interacts and or changes state that is truthful and measrueable. But that only works if gravity interferes.

Without gravity what else would cuase a relative change in velocity ?

Back to that thing abotu constants.

There are no universal constants. It makes humans feel better about the universe but the speed of light is just that. The speed of light. Now how the speed of light is a behavior of photons vs atoms and how matter interacts as we observe it with layer os complexity above and below the level of photons. the speed of light may have a boundary area that is typical. There may be some cosmilogical truth in the speed of light IE particales of a given size may only travel at X velocity. . However it is not a constant. Simply a state of existance.

Its not that I don't "Get" the physics. Its that I think alot of it is bullshit and I don't mind saying so.

Hence the underlying socialogical issue with humans.

We assume to much and solid numbers make us feel better.

BTW I know I am wired differently and its ok with me. I can do complex 3d modeling in my mind eye and all sorts of virtual tasks.

I can build complete circuts or engines or 3d objects and look at grain structures as if they were right in my hands. I also can do nonlinear thought and can abstract as well as do projection and 3dimensional charting with near pinpoint accuracy. All without a pen or paper. I can crunch numbers to minute decimal places.

I can take any object I may have assembled and disasembled and blow it apart into a 3d rendering as if it were a cad cam drawing. I can also compose music in my had and translate it directly to paper. I can also recal every piece of music I have ever heard in my life with crystal clarity as if it was played aloud for the world to hear.



but I admit. trying to get out what I can easily comprehend in english. Not always so easy. Not only that It comes with a heavy penalty in terms of social skills. I do get along however.

but the blessing is also a curse.

That sounds very familiar in an awkward way.

Are you left handed by any chance ?

You remind me of an visual thinker.
The theory i read once is an overdeveloped corpus callosum which presents the possibility of more data being transferred simultaneously between the hemispheres who themselves are already wired differently. Not to confuse with hyper connectivity, that is something different or at least a different result. As if the dominant logical part of the brain is able to "load and program" that part of the brain that decodes visual data like body language and facial expressions. Similar as having a logical control alu together with an programmable dsp rather then a dsp with a fixed internal rom. The alu works temporal or sequential, the part of the brain that decodes vast amounts of visual and audio information at the same timeframe does so highly parallel. That gives the ability to see things without taking time into account and keep track of lots of variables at once. But can create the situation where other people can not follow unless they see it. This also explains why visual thinkers can burn themselves up quite easy. This visual capability and the ability to think in parallel is quite a natural high. The rest of the brain is not used to the vast amounts of blood that is need to keep on feeding and not to forget cooling of the brain. (The eyes are cooled as well by large amounts of blood because of the large amount of processing) The brain seems to use up to 25 % of the daily energy needs in an average build person. Not bad for a lump of flesh of on average 1/30 of the entire body weight(80 kg person average person).

But then again it is al theory since it is quite new and only been proven by circumstantial evidence.
The part of the brain doing the visual decoding is also used for decoding of sounds according to brain research with fmri.
http://www.grandin.com/inc/visual.thinking.html

EDIT:
Forgot to mention one thing, all humans are natural image thinkers. The problem is that humans as children are forced to not think in images and most loose the ability at around the age of 10. Effectively dumbing them down. Others keep the visual ability only to feel awkward and uneasy when being around people who have unlearned this vital human advantage(logical image thinking) over animals.

 

[Daedalus685]

Dark matter is NOT dust. This would be detectable by absorption spectra, black body radiation, etc.

Do you know what weakly interacting means? Regular matter, the stuff we're familiar with, is not weakly interacting. You can't have both of those things in one answer.

Also, gravitational lensing effects HAVE been observed & provide evidence of the existence of dark matter. We just don't know what dark matter is. But, we DO know what it isn't. It isn't made up of things like protons and neutrons and electrons.

There's plenty of understandable material here:
http://en.wikipedia.org/wiki/Dark_matter

I did not mean to imply that all dark matter were not Wimps... But the dark matter definition I'm most comfortable with refers to simply uncounted for mass.. which includes all of the things you mentioned including conventional matter. It is not that which cannot be detected but that which has not been. I don't think you appreciate how difficult even utterly boring stuff is to see if sufficiently isolated.

There could be billions of brown dwarf stars floating about beyond the rim and we may never notice them directly.

Lately it seems most people refer to it as that which cannot be detected though.

Modest linked an article claiming a discovery to make up for matter as proof dark matter doesn't exist.. When in fact if that were the case (it isn't) it woudl be the dark matter that was found. We would just be a bit off on teh assumption of its WIMP composition.

The problem is we assume we know what it isn't.. but we actually have not eliminated anything as a possibility yet for 'all' of it. Give it time though. What we do know though is what it all likely isn't. It is likely not all conventional matter, in fact most is not. This boils down to the shere amount we need.. if it were there we would see 'some' optical effect (dimming of light from outside galaxies and so forth). But it could be explained using conventioanl matter.. it just requires a list of explanations as long as my arm in should have and could have. It is more likely it is weakly interacting as opposed to in exactly teh 'wrong' spot.

My appologies if I confused anyone.. It is surely mostly WIMPs... but if like modest pointed out we discover new matter locations it doesn't prove dark matter doesn't exist.. it proves tahat we found it.

Edit: To continue babbling.. but to put it in perspective.. We can see local extragalactic dust clouds down to a temperature of about 20K. Remarkably cold but there are still a lot of colder locations between what we call the galaxies.

 

[Daedalus685]

A bit on what dark matter is and how we know that it is likely (though not certainly) soemthing non baryonic as many seem interested in it.

Here is a good story about it:

http://scienceblogs.com/startswithabang/2009/09/dark_matter_part_ii_how_much_n.php


What we know can be broken into several parts. We know that gravetational data indicates there should be more mass (for galaxy rotation and large scale structure) that the the composition of the universe is not such to account for all of the energy during nucleosynthesis, that the CMB indicates there is something non baryonic, and that we simply don't observe enough of the mass (gas or otherwise).

That being said, we can't possibly observe everything, the universe is too large to even know fully what lies in our solarsystem let alone the galaxy cluster. So not seeing it is no reason to asume it is something special.

Here is the article about what dark matter likely is by the same fellow:

http://scienceblogs.com/startswithabang/2009/10/dear_mond_time_for_a_new_song.php

http://scienceblogs.com/startswithabang/2009/10/what_is_dark_matter.php

We don't know exactly how much there is.. There are likely structures of normal matter we don't understand and our estimates are a bit high (that is why we give a range of things after all.

That something else is out there is a valid theory because it would take numerous small specific and hand wavey modifications to a vast number of ideas that do not aply elsewhere to explaining via gravetational means.

Does this mean it has to be there? Of course it doesn't. But it is likely that soemthing we don't understand is at play here rather than a perfect placement of things we do understand but avoid.

Oddly enough Machos are no longer considered candidates.. which has changed since school!

Oh well, glad things do change, as ther is a lot more evidence today than there was 5 years ago.

So no, dark matter is not considered dust.. though if we do find a whole whack of regular matter somewhere we could explain many of the observations we currently attribute to dark matter and confound the others even more.

It was sloppy of me to alude to it being largely regular matter as opposed to it 'could be' regular matter. There is also no guarantee that galaxy rotaion is due to dark matter at all.. only that it makes sense that all of these problems are explained by the same thing.


Edit: Nasa still considers MACHOs a viable explanation (regular matter objects compact enough to not interfere with light but masive, they inclclude extra galactic brown dwarves) but many of the papaers I am readign that are more up to date seem to discount them on the basis of the new simulations involving cold dark matter heavey universes. Nice that thigns change so fast, sorry for being out of touch a tad.. I looked up my cosmology book and they had almost equal mention of MACHOs to wimps.. at the time (only 4 years gone by) most of the professors seemed to like them better too.. I suppose the point is that we don't know.. Though it seems very likely that the mass is not in the form of baryons.

For anyone interested:
http://arxiv.org/PS_cache/astro-ph/pdf/9904/9904401v1.pdf

That is a good paper on why MACHOs are likely not the bulk of the mass (we would have to be wrong about the nucleosynthesis mechanisms during the big bang for themto exist as there woudl not otherwise be enough baryons).. Man, I feel so out of touch.. so easy to not keep up with anything I don't do for a living.. lol. Thanks for asking questions and making me look up more modern papers guys!

 

[waffletten]

You folks should check out these lectures from the real deal (Hawking and Schmidt), much better than wikipedia, a 1999 paper from a small group at the U of M, or some blog. The Schmidt lecture is awesome (50 minutes) and covers your discussion, the Hawking lecture is too short but still informative.
http://www.tvo.org/TVO/WebObjects/TVO.woa?videoid?91400085001
http://www.tvo.org/TVO/WebObjects/TVO.woa?videoid?101494255001

As is the case in all physics, there is still quite a debate on many of the things you discuss (Susskind vs Hawking on black holes, for example). I love their debates.

That sounds very familiar in an awkward way.

Are you left handed by any chance ?

You remind me of an visual thinker.
The theory i read once is an overdeveloped corpus callosum which presents the possibility of more data being transferred simultaneously between the hemispheres who themselves are already wired differently. Not to confuse with hyper connectivity, that is something different or at least a different result. As if the dominant logical part of the brain is able to "load and program" that part of the brain that decodes visual data like body language and facial expressions. Similar as having a logical control alu together with an programmable dsp rather then a dsp with a fixed internal rom. The alu works temporal or sequential, the part of the brain that decodes vast amounts of visual and audio information at the same timeframe does so highly parallel. That gives the ability to see things without taking time into account and keep track of lots of variables at once. But can create the situation where other people can not follow unless they see it. This also explains why visual thinkers can burn themselves up quite easy. This visual capability and the ability to think in parallel is quite a natural high. The rest of the brain is not used to the vast amounts of blood that is need to keep on feeding and not to forget cooling of the brain. (The eyes are cooled as well by large amounts of blood because of the large amount of processing) The brain seems to use up to 25 % of the daily energy needs in an average build person. Not bad for a lump of flesh of on average 1/30 of the entire body weight(80 kg person average person).

But then again it is al theory since it is quite new and only been proven by circumstantial evidence.
The part of the brain doing the visual decoding is also used for decoding of sounds according to brain research with fmri.
http://www.grandin.com/inc/visual.thinking.html

I am no expert on physics, but have published a few papers in Neuroanatomy, Biochemistry, and Pharmacology. Grandin is an livestock biologist whom studies animal handling and has a side interest in autism (which she believes she has). Like autism her theories are controversial, and the subject of much debate. She is an expert on the handling and care of livestock, not neuroanatomy.
So, in essence you are describing an autistic brain, not a "visual thinker", from the link you provide. BTW, I have actually met and talked to her at a few meetings when I was presenting stuff on facial motor control in the cerebral cortex. She is a nice person and very passionate about autism.

 

[Daedalus685]

You folks should check out these lectures from the real deal (Hawking and Schmidt), much better than wikipedia, a 1999 paper from a small group at the U of M, or some blog. The Schmidt lecture is awesome (50 minutes) and covers your discussion, the Hawking lecture is too short but still informative.

Hehehe, take that UofM!

That paper was published a bit ago but it takes time for things like that to get into the limelight, case in point it is about MACHOs not really being a big deal (har har) yet they were still covered extesively as a possibility (though not a huge one) when I graduated in 2007.. the quality and whatnot should not be of question though. Small perhaps.. but Hawking doesn't exactly work with a large group either. Next time I'll only use papers from perimeter though. But then you might try to tel me how Waterloo doesn't count either!! (Though the chair of perimeter is hawking )

As for the blog, Ethan Siegal is not exactly me and actually has his PHd in theoretical cosmology. His blog is awesome for explaining things one may not have taken for years in school.. I wish I took more chromodynamics...