Image: Illustration by Don Dixon
In Brief
- Dark matter is one of the great scientific mysteries of our time, but once astronomers accepted its existence, the answers to many other cosmic mysteries fell into place.
- Whatever this unknown material may be, it seems to explain why the disk of our Milky Way galaxy has such a pronounced warp at its outer rim. Orbiting satellite galaxies naturally tend to distort the galaxy, but their gravitational effect would be too weak without the amplification that dark matter provides.
- Another question dark matter answers is why the Milky Way appears to have fewer such satellite galaxies than models predict it should. It turns out that the satellites are probably out there, though composed almost entirely of dark matter, making them hard to detect.
More In This Article
Although astronomers only slowly came to realize dark matter’s importance in the universe, for me personally it happened in an instant. In my first project as a postdoc at the University of California, Berkeley, in 1978, I measured the rotational velocities of star-forming giant molecular clouds in the outer part of the disk of our Milky Way galaxy. I worked out what was then the most accurate method to determine those velocities, and I sat down to plot out the results (by hand on graph paper) in the astronomy department lounge. Two other experts on the Milky Way, Frank Shu and Ivan King, happened by. They watched as I filled in the velocities of the outermost clouds, and the pattern we saw made it clear at once that the Milky Way was rife with dark matter, especially in its outermost parts. We sat and scratched our heads, imagining what the nature of the dark matter could be, and all the ideas we came up with turned out in short order to be wrong.
This study was one of many in the 1970s and 1980s that forced astronomers to conclude that dark matter—a mysterious substance that neither emits nor absorbs light and reveals itself solely by its gravitational influence—not only exists but is the dominant material constituent of the universe. Measurements with the WMAP spacecraft confirm that dark matter accounts for five times as much mass as ordinary matter (protons, neutrons, electrons, and so on). What the stuff is remains as elusive as ever. It is a measure of our ignorance that the most conservative hypothesis proposes that dark matter consists of an exotic particle not yet detected in particle accelerators, predicted by theories of matter that have not yet been verified. The most radical hypothesis is that Newton’s law of gravity and Einstein’s general theory of relativity are wrong or, at the very least, require unpleasant modifications.
This article was originally published with the title The Dark Side of the Milky Way.
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29 Comments
Add CommentIn a nutshell and with everything this article has brought together, it seems that dark matter is what created the Universe and holding it all together and separate. The particles in the dark matter could be dormant atoms (that's why it is dark) that was used somehow to ignite and create everything we now see and can't see...you can do a lot in 14+ billion years at the speed of light. When a number of different atoms are needed to create a star or a planet (which should be the simplest to create), dark matter activates the atoms needed and sends them out where gravity pulls the atoms together. I know that sounds simple, but the Universe is not as complex as you may think since everything around us, and including us, was created from individual atoms...or at least that is what my third-grade science teacher told me. Something had to created all this, so why not blame it on dark matter and the simple atoms it may hold in storage? That would also mean that there was no 'big bang'...just atoms leaving the roost to be towed by gravity to their new destination.
Reply | Report Abuse | Link to thisI think the dark mater exist.
Reply | Report Abuse | Link to thisHubble and firedman say the universe expand and i think the dark mater is one elastic material.
I know this is speculation because nobody scientist prove this.
But if the universe expand and dark mater is one kind strong gravity that make the universe joined, he is one "plastic" material. Correct me if i wrong.
This is one opinion.
We haven t technology to study this because are litle particules.
someone give me more explanation
Leo Blitz - You stated:
Reply | Report Abuse | Link to this"They watched as I filled in the velocities of the outermost clouds, and the pattern we saw made it clear at once that the Milky Way was rife with dark matter, especially in its outermost parts."
Can you please explain exactly what was the "pattern" you saw in the velocities of peripheral clouds that "made it clear at once that the Milky Way was rife with dark matter, especially in its outermost parts?"
Am I correct to presume that the pattern you refer to was the 'flat' or even increasing rotational velocity as a function of distance from the galactic center?
If so, am I correct to presume that you concluded 'at once' that some dark matter must be present primarily because the orbital velocities derived from observation did not comply with Keplerian rotational curves?
I would greatly appreciate any enlightening clarifications you can provide.
Sincerely,
James T. Dwyer
i luv d mysteries of universe. One theory gives d answer to some sets of questions but mystifies the other questions.
Reply | Report Abuse | Link to thisWe all came from timeless and dimensionless light and will turn into light when we shed our material bodies. Those of us attracted to material world will continue to live in this everchanging pit of dark hole without light.
Reply | Report Abuse | Link to thisThe reason why the sun has not burned out is because it is ever in the process of gathering in new fuel, courtesy of the stray quarks of dark matter coming together to form the 1st element in our 4 dimensional world.
Reply | Report Abuse | Link to thisThe reason why not enough mass has been found to reverse the red shift from the outermost stars is because this mass has not been created yet.
The reason why 19.47 degrees repeats as an anomaly throughout our solar system is because it is the angle of refraction between the higher and lower dimensions (much akin to the one we can see between air and water).
A transposition of Einstein's formula, written as E over C squared equals M, shows the relationship pertaining to the creation of mass from the coalescing, super energized stray quarks of dark matter.
Quanta packets of light are actually a halfway house between the higher and lower worlds. Without resurrecting parts of the old Aether theory we are left without a medium for the transfer of energy. The truth is that the dark matter is the Aether and the Aether is the dark matter.
The super-energized,stray quarks of dark matter travel faster than the speed of light but when the organize to become quanta packets they become subject to the laws of light. Joe Richardson
When an electromagnetic wave is absorbed by a metal plate with mass M, M increases with the square root of (1-v²/c²)and its velocity also increases due to the energy transfer from the wave to the plate. This leads to the equation E=mc² which is not Einstein's equation, Poyncare and Hasenoehrl had derived it before 1905. Einstein claimed that it can be derived form the Lorentz trandformation, which is wrong as Max Planck had shown in 1907 because mass increase cannot depend on the choice of the observer platform. How absurd Einstein's claim is can be explained this way: the sun's mass cannot increase due to tne observer jumping into a rocket and flying,say, to the moon with it. Thus special relativity is predicting nonsense in this respect. In SCIAM's issue of March 2009 Albert and Galchen had explained why special relativity is incompatible with QM (entanglement). Anything derived from special relativity is nonsense!
Reply | Report Abuse | Link to thisRead ether=gravity=dark energy theory of gravitoethertons,Misjudgements by Newton, Balloon inside balloon theory of matter and antimatter universe on opposite entropy path producing gravitoethertons which we call dark energy .The papers are available in ASTRONOMY.NET .published in year 2002.
Reply | Report Abuse | Link to thisSometimes just before I fall asleep I turn my mind to the question of Dark Matter and Dark Energy in some forlorn hope that my unconscious Mind will solve the question while I sleep. Not surprisingly, I must confess that, so far I have had Zero success. One of the major problems anyone has when trying to decipher the overall make-up of our Universe comes from the fact that we are a part of it. It would be oh so simple if we were able to stand “outside” and get a Panoramic snap shot of it, as a remote observer would have. This is the “real” dilemma facing us. So we are relegated to deducing its make-up by using Mathematical constructs to describe what we observe and then interpreting the logical predictions derived from them. Seems like a primitive second-handed form of predictive methodology when you really think about it, but is probably better than tossing animal bones on the ground and drawing conclusions from their random placement.
Reply | Report Abuse | Link to thisWe come up with theories that seem to describe, with some degree of accuracy, that which we observe and we gleefully polish them up and put them on a pedestal for all to worship. Then along comes a new theory that either disproves or brings into question the preceding ones and those who have paid homage to the theories of the past fight tooth and nail to keep their favorite ones in favor. Perhaps this is a good thing since the resultant adversarial contest is not unlike the Evolutionary “survival of the fittest contest”, which dictates that those which survives must by necessity be the most able to adapt to their surroundings.
Take for example that time honored and revered theory that nothing travels faster than the speed of Light. There are currently experiments being carried out in an attempt to verify a recent observation that Neutrinos may have in fact broken even that barrier. Does this mean that the old theory was in error? No, if this turns out to be true, what it means is that all of the observations supporting it were correct for their Time and Place. If we are ever to decipher the Equation describing the Totality of the workings of our Universe, if such a thing actually exists, we will probably smile at the childish arrogance we once had and marvel at the fact that we, who occupy such a miniscule physical part of the Totality of the whole, could ever even contemplate that we could fully understand the Totality. Consider this: what if the Totality itself, and the Laws governing It are Evolving Entities in their own Right?
If you go to the subatomic level waves behave like particles and the Newtonian model does not describe things adequately. So why not some similar process at the other end of the scale. At macro scales different rules predominate. Possibly the atoms in those distant galaxies are different sizes than the ones on Earth, for example the further away they are the bigger they are. Imagine an oxygen atom and its subatomic particles 18 times bigger than the ones you breathe. Perhaps at one stage in the dim past that were all mixed together but slowly separated out into different regions in space to form a spectrum of masses. The thing is, you cannot assume that the laws of physics on Earth hold for things at great distances, you have to accept that there may be differences. Now, if they are looking for a name for this dark matter, I suggest they call it Lavatorium, after the ditty, 'Oh dear, what can the matter be? Two ladies locked in the lavatory...'
Reply | Report Abuse | Link to this"Although astronomers only slowly came to realize dark matter’s importance in the universe, for me personally it happened in an instant."
Reply | Report Abuse | Link to thisNext time you write about this, please include the INSTANT!
Or, was that a quantum instant taking place over a dark matter influenced, time-distorted 'instant'... it certainly was of no help to me in peering into your mystery.
"dormant atoms"? Really. As in what, like, not vibrating? Waiting for the lights to come on?
Reply | Report Abuse | Link to thisCome on; really? Dormant atoms?
The CERN Experiment on fast neutrinos is easily explained by the motion of the earth in the direction constellatioin LEO, its speed is 370km/s (Smoot Nobelpreis 2006) All particles are influenced by this motion with respect to the Aether (Cosmic Microwave Background). CERN scientists probably know that, they have heard my talks on the Aether given at the European Physical Society Meeting in Poellau, Austria in 2010 ("echophysics")
Reply | Report Abuse | Link to thisNo one even knows if Dark Matter actually exists. It may be, in fact, a polite fiction, created by scientists, to keep their precious General Theory of Relativity from being hopelessly wrong. Perhaps new theories are in order.
Reply | Report Abuse | Link to thisas to the two gentlemen: O ha ha haha ha ha ha...
Reply | Report Abuse | Link to thisThe Universe on the Wrong Side of the Tracks
Reply | Report Abuse | Link to thisThe Low Gravity Ghetto of Cosmology
The geometry and properties of space diverge along two formulations, according to whether matter or space is dominant. Space brings Time to the table, it is not just a container. When matter is dominant, Space Time and GR are correct. When Time Space is dominant, GR and Newtonian physics cannot make correct predictions about things like galactic velocity curves.
A point that people miss about the flattened velocity curves, why don't stars with same velocity collapse into a single toroidal mass, when they are disturbed by an external force? Dark Matter could not prevent it.
If all the stars had the same kinetic energy per mass unit, nothing could prevent it.
It appears that our universe is bipolar. It has two competing and divergent forces. Matter, energy, and gravity on one side, and space and time on the other side.
Another problem is an assumption about the flow of time. Why can't it go faster than 1. Did anybody ask Time it's opinion of these limits?
Modern physics may have missed out on how more than half the universe works, when physics assumes that time can't go faster than 1. How fast does time flow when there isn't any matter or gravity around? Is infinity an interesting number?
I refer to your feature artcile “The Dark Side of the Milky Way” in the 1 st of October 2011 issue of Scientific American. As a practising telecommunications engineer in Australia I was also inclined to accept cosomology theories that the universe was expanding and that at an earlier time it had contracted into a signularity. That was before measurements of the elongation of the wavelength of distant objects were accompanied by only one interpretation, which is the universe is expanding at increasing rates of acceleration. This more recent theory relies upon dark energy and dark matter to explain 80 to 90% of the observed shift. The extent of this relience turns it into dark theory.
Reply | Report Abuse | Link to thisTo varying degrees the cosmology theories rely on a universe that has a finite boundary. Without a boundary the argument in favour of a sole singularity looks less plausible. But the observed boundary is actually the limitation of the sensitivity of the equipment used to make these observations. Maps of the universe have been presented in oval form whereas it is actually circular with the observer dead center. That is we are allegedly at the center of the universe again. However there is no scientific proof that the physical boundary of the universe is 13.7 billion light years away or for that matter 100 billion or a trillion-billion light years away. There is a vast amount of knowledge that is unknown to us.
What is known is that the farther away the object is, the larger is the observed elongation of the wavelengh. Scientific discovery will be better served if similar amounts of lateral thinking are put into alternative explanations for the elongation of the wavelength. For example detectable radio waves may alternatively arise from the elongation of electromagnetic waves orginating from objects beyond the presumed boundary. And this observation may not be attributable to background radiation nor objects receding at increasing rates of acceleration. If the horizon of the universe is farther than thought it suggests that the observations are either explained by exponentially increasing amounts of dark energy and dark matter or by none at all. In conclusion there is scope for more than one dark theory to explain these observations.
It see 's to me that the presence of what we think of as dark matter is an unexplainable curvature of space-time. In the article I get the impression that there are a whole bunch of shadow-star-systems whose gravity we feel but that don't seem to be part of our.... Universe? Gravity is so poorly understood! If it is the backbone if what space is, and we assume ( as modern science does) there are other universes out there that are together with ours part of one multiverse, why would the effect of gravity be confined to a single universe?
Reply | Report Abuse | Link to thisIf this gravitational effect exists, maybe it can also lead to an understanding of an even more exotic fenomenon, namely dark energy, with others words the fact that some mysterious force accelerates the expanding of our universe.
So the space-time fabric expansion of the universe is accelerating. The symptoms of acceleration are the same as those of gravity. May gravity just be the result of ordinary matter falling together as a result of the accelerated expansion of the fabric it is on? Please someone check by comparing the rate of acceleration with the gravitational constant!
Reply | Report Abuse | Link to thisquote: dark matter—a mysterious substance that neither emits nor absorbs light
Reply | Report Abuse | Link to this--------------
While the air cell is expanded its aura (nuclei) are of a size that does not interact with the sun's radiation and little light is produced leaving a dark cloud (black). The vortex of energy released from the Earth has now mutated to a size as to interact with gravity and air, returning to Earth as a destructive tornado.
quote: What the stuff is remains as elusive as ever
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Dark matter of outer space is made up of info cells of all Earth. We are not made for this planet but are made of it. It is the reason for the familiar make up of life in times past.
If there is a nook or cranny any where in our Universe that conditions will allow evolution of Earth life, it has happened.
quote: The CERN Experiment on fast neutrinos is easily explained
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We have been led to believe that thunder is the after math or results of lightning when in fact the opposite is true!
Thunder (the collapse of air cells) creates the energy of what we call lightning.
Thunder happens first!
Sound travels much faster than light !
The sound that we play around with is leftover energy of reactions that have magnetically regrouped into larger chips (molecules). This leftover energy is just one in many that an air cell has as it’s nucleus!
Considering new technology, and I was listening from the Moon “I would hear your whistle before you would!”
quote: cosomology theories that the universe was expanding
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Sending a satellite into orbit we know the thing is orbiting in a circle but sending it away from Earth it’s god only knows where it will end up. My discovery shows this satellite coming right back to where in space it was launched from. It will make many turns in its travels but and is never to, that far away from home!
quote: gravitational constant!
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It is not known that true gravity (weight) is in constant change and those days that you feel light and bouncy and the times you feel heavy YOU REALLY ARE!
quote: hypothesis is that Newton’s law of gravity and Einstein’s general theory of relativity are wrong
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Debunking the likes of Sir Issac Newton, Einstein, my Science teachers, I bloody well will have to do better than the preceding.
http://www.physforum.com/index.php?showtopic=11418
What we see is that thirteen billion years ago galaxies were moving away fast, but ten billion years ago, they weren't moving quite as fast. At eight billion, even slower, and so on until, in the recent past (close objects), they aren't moving away at all. In fact the Andromeda galaxy is moving towards us. This seems totally contradictory to the accelerating expansion theory
Reply | Report Abuse | Link to thisIt will take a bit of pondering but respectively chew on this one.
Reply | Report Abuse | Link to thisWould it not be nice to understand new true science of why and how things are attracted and stick to each other, really simple STUPH! (not complicated at all)
Explaining why the quark, molecule, cell, atom, magnetism etc attract and repel would soon have eyes glazing over. I will make it real simple for you to understand why bread crumbs don’t stick to the plate yet toast crumbs and egg do, why snow flakes and rain drops are separated.
OK this is what you do. Sit your-self down in front of the six o’clock news and take note of the weather report. Animation shows the high pressure area (clockwise) and close by will be a low pressure (counter clock wise). If you look carefully its easy to see the forces of the low melding into the forces of the high (attracting). Looking closer, take note that the forces of the high and low merge into a figure 8 and thats how every natural thing having multiple orbits is held together. Look for two highs or two lows and you can see where the forces are running into each other (repelling).
Take this to the smallness of the quark or the hugeness of the heavens and Bobs your uncle!
Leo Blitz - As you stated in your opening anecdote,
Reply | Report Abuse | Link to this"I filled in the velocities of the outermost clouds, and the pattern we saw made it clear at once that the Milky Way was rife with dark matter, especially in its outermost parts."
What you do not explain is that, like Vera Rubin and other astronomers had done earlier, the reason that the "pattern [you] saw made it clear at once that the Milky Way was rife with dark matter" was simply that you had expected that rotational velocities of disc objects should diminish as a function of their distance from the galactic center. That's the only evidence that was necessary to convince you that some still unknown form of undetectable matter not only existed but dominated the material universe.
However, those more distant peripheral halo objects you later referred to DO exhibit Keplerian rotation curves! What is the difference between objects within the enormous galactic disc and more distant halo objects that produces these distinct rotational characteristics? In simple terms, the galactic disc rotates as a loosely bound, self-gravitating object whereas discrete halo objects independently orbit the distant galactic bulge (where one exists) and disc as a single point-mass!
Please refer to my comments and references at:
http://www.sciencewithoutfiction.com/uploads/JDwyer.PDF
Regarding the asymmetry issue (and idependant influences): (Sorry, not a scientist, but every time I read or hear about dark matter, the same question pops into my head.) Dark matter is said to neither absorb nor emit light. I assume that that means it is not impacted or influenced by light(doesn't reflect it, is not lit up by it, is not energized by it, etc.). It has always seemed curious to me that we have always defined everything, even the maximum speed of anything, by the mechanism we have used to look at it, i.e., light--or some variation of it. We seem to be inherently limited by the "flashlight" we are using to hunt for our lost keys. Is it possible that matter (the regular kind) and dark matter, while influencing each other via a common gravity-connection may be independantly or uniquely influenced by forces limited to or restricted to the seperate realms of (regular) matter and dark matter. Solar winds come to mind. Would they not impact (regular) matter without impacting, directly, dark matter; thus causing a kind of dynamic asymmetry that would look to us like static asymetry, but is in fact, like the wobble, a dynamic "shape"?
Reply | Report Abuse | Link to thisDark matter is merely a gravitational proxy: astronomer's gravitational approximations infer the existence of matter that exceeds their mass estimates for large scale aggregations of discrete objects.
Reply | Report Abuse | Link to thisThis finding indicates that either:
- Astronomer's estimations of gravitational effects (necessary to explain the rotational velocity of objects within the periphery of galactic discs, for example) is in error
- Astronomer's estimations of galactic mass (often based on observed luminosity) is in error
- Some unidentified, undetectable form matter accounts for the perceived gravitational anomaly.
Astronomers generally favor option 3...
Supposing that there was no 'big bang?
Reply | Report Abuse | Link to thisThat first there was a rotational big squeeze - and, that the dark energy was so compressed in the reduced space that it 'phased' into a denser substance i.e. Dark matter.
Then baryonic matter was'ignited'/created, within this evolving rotating 'mass' and the resultant energy helped drive the expansion of the Universe.
Marg, Allworth.
Suppose there was no big bang - but instead a big rotational squeeze?
Reply | Report Abuse | Link to thisAs the dark energy was compressed and squeezed it'phased' into a heavier substance i.e.dark matter.
This then, with further pressure ignited/created the baryonic matter that we are all part of helping to drive the expansion of the Universe.
Marg, Allworth.
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Reply | Report Abuse | Link to thisF=MA does not apply to gravity. Gravity is a change in the structure of space and as such has no 'force'. Acceleration and momentum changes 'happen' but there is no force.
Reply | Report Abuse | Link to thisWhat we think of as space is a 3D coordinate system. What 'really' exist is more like lake water filling up that 3D system. For this we need 'space particles'. It seems 'space particles' have at least three functions. 1) These separate the here from the there. (Matter absorbs these particles and as a result we have gravity.) 1.5) As partilces are absorbed everything is a bit closer together. 2) these particles are like a raft 'following' matter about, this lets us have Non-Additive-Motion, light moves at this one speed in the vicinity of the Earth and differently near other bodies.
3) Light speed exists in relation to these underlying space motions, therefore light becomes bent by a gravity well as well as seemingly faster in different locations.
"Relativy vs Non Additive Motion" is a google.com/knol. Please read and try to understand. Michael
PS: A non dark matter possiblity exists as the Universal Law of gravitation is inaccurate, so that stars have more 'force of gravity' than expected. And/or. There is a disconnect as it is 'space particle' absorbtion and not some 'force' that causes these motions.