It is well documented that dark matter makes up the majority of the mass in our universe. The big problem comes when trying to prove dark matter really is out there. It is dark, and therefore cannot be seen. Dark matter may come in many shapes and sizes (from the massive black hole, to the tiny neutrino), but regardless of size, no light is emitted and therefore it cannot be observed directly. Astronomers have many tricks up their sleeves and are now able to indirectly observe massive black holes (by observing the gravitational, or lensing, effect on light passing by). Now, large-scale structures have been observed by analyzing how light from distant galaxies changes as it passes through the cosmic web of dark matter hundreds of millions of light years across…
Dark matter is believed to hold over 80% of the Universe’s total mass, leaving the remaining 20% for “normal” matter we know, understand and observe. Although we can observe billions of stars throughout space, this is only the tip of the iceberg for the total cosmic mass.
Using the influence of gravity on space-time as a tool, astronomers have observed halos of distant stars and galaxies, as their light is bent around invisible, but massive objects (such as black holes) between us and the distant light sources. Gravitational lensing has most famously been observed in the Hubble Space Telescope (HST) images where arcs of light from young and distant galaxies are warped around older galaxies in the foreground. This technique now has a use when indirectly observing the large-scale structure of dark matter intertwining its way between galaxies and clusters.
Astronomers from the University of British Columbia (UBC) in Canada have observed the largest structures ever seen of a web of dark matter stretching 270 million light years across, or 2000 times the size of the Milky Way. If we could see the web in the night sky, it would be eight times the area of the Moons disk.
This impressive observation was made possible by using dark matter gravity to signal its presence. Like the HST gravitational lensing, a similar method is employed. Called “weak gravitational lensing”, the method takes a portion of the sky and plots the distortion of the observed light from each distant galaxy. The results are then mapped to build a picture of the dark matter structure between us and the galaxies.
The team uses the Canada-France-Hawaii-Telescope (CFHT) for the observations and their technique has been developed over the last few years. The CFHT is a non-profit project that runs a 3.6 meter telescope on top of Mauna Kia in Hawaii.
Understanding the structure of dark matter as it stretches across the cosmos is essential for us to understand how the Universe was formed, how dark matter influences stars and galaxies, and will help us determine how the Universe will develop in the future.
“This new knowledge is crucial for us to understand the history and evolution of the cosmos […] Such a tool will also enable us to glimpse a little more of the nature of dark matter.” – Ludovic Van Waerbeke, Assistant Professor, Department of Physics and Astronomy, UBC
Source: UBC Press Release
I think the picture in this article has been published here before, and has nothing to do with the actual study at hand, does it.
dark matter is not believed to hold 80% of the universes mass, and also neutrinos and black holes have nothing to do with dark matter. They are both made of ordinary elemntary particles included in the estimated 5% of ordinary matter that fills the universe.
Afaik, the current estimation is that the universe is filled with
5% ordinary matter (stars, planets, gases, nebulae, black holes, neutrinos, anything you can imagine)
25% dark matter (some weird other stuff you can’t imagine, or at least not detect atm)
70% dark energy (supposedly the force that drives the universe apart between any two given points, expanding our spatial dimensions, something like anti-gravity 🙂 )
This article seems to have been written by someone who neither understood the nature of the (still theorhetical) dark matter, nor even the distinction between dark matter and dark energy. The first line: “It is well documented that dark matter makes up the majority of the mass in our universe.” Contains two factual errors. 1.) Dark matter makes up perhaps 25% of the universe, and 2.) it is widely hypothesized, but hardly well documented. In fact, there is no direct evidence of the existence of dark matter to date.
We infer the existence of dark matter and dark energy by observing effects for which we can see no cause, and deducing that something (dark matter/dark energy) must be responsible for the observations.
But dark matter is not the only thing that might produce gravitational lensing, and dark energy is not the only viable explanation for why empty space has a negative energy constant.
The expansion of the universe could as easily be driven by forces which do not reside in the realm of 3-dimensional matter. Current theories do provide for such mechanisms, but astronomy is drawn to the dark matter hypothesis because it means no messy mucking about in multidimensional cosmology.
The oversimplification in this article reminds me of the STNG episode where the ship encounters a “cosmic string”, which is depicted on the screen as a big shimmering rope, undulating through space. I laughed so hard, dark matter came out of my nose.
Columnists should at least understand two things: 1.) Science is the process of poking around in the dark with a pointed stick. Just because you poke something soft does not mean you can assume it’s a teddy bear. 2.) science is slow and not particularly sexy. For fast and sexy, we have science fiction.
Let’s avoid confusing the two.
Wow.. nice peter pan.. Maybe we should head over to your favorite boards and label you…
Anyway… Just a thought.. upon collapse there is not enough matter in a molecular cloud and it collapses to a dark solar system. IE no sun just planets. We could not see or detect them however a solar systems gravitational influence would be enormous.
Geez, how I love the funny papers this site publishes. Hole lotta theory here, but, pardon the pun, not much substance. When oh when will there be a new theory that doesn’t depend on “dark” this and that.
What in the world has set Peter Pan’s teeth on edge? I think the article, even with it’s “errors” and the comments by Scott and Aleksik are all interesting, thanks to all of you. I’m glad there are people who will share their knowledge and ideas.
Hi CrackPot Prof,
There is such a theory, and at present, it holds solid speculative answers to ALL of the most nagging questions of cosmology–including the question “what happened prior to the Big Bang.” It’s M-Theory, and it’s stunningly elegant from a mathematical perspective.
The problem is, M-Theory allows that most of what’s going on in the universe is happening in dimensions that we can’t even perceive. This makes it very difficult to gather experimental evidence for M-Theory… until we can develop measuring devices that can operate beyond 4-D spacetime.
Some of the more profound correlative math for M-Theory (which is a convergence of all viable String Theories combined with Supergravity Theory) suggests that gravitation is not a native force, but rather more like “leakage” of a dynamic force from an ajacent “membrane” in 11-dimensional space.
Since astronomers absolutely cannot observe anything beyond three dimensions of space and one dimension of time, they tend to think of M-Theory as “pie in the sky,” just as they did with Special Relativity until it’s predictions started proving true. Rather, astronomers constrain the universe to these four dimensions, and expect to find all causes and effects to be observeable in the EM spectrum. So when they come across an effect without an observeable cause, astronomical theories invariably lean toward “we just need a better telescope.”
But with Dark Matter/Energy, it is quite possible that they’re looking in the closet for a coat that’s hanging in the hallway. There is no evidence that what they are looking for MUST be resident in our spacetime, and MUST be expressed in the form of exotic matter. It’s certainly possible… but FAR from firmly established.
Very well said W. Scott and LMAO at the dark matter coming out of you nose…that was funny !
There are so many issues with STNG that it makes me laugh too, and ultimately you are correct, the dark matter/energy issue is all theoretical at this point. I do suspect that the limitations of 3D has something to do with the mystery, but I could be wrong.
I guess we just need to keep working on advancing the technology to better test what’s out there.
Dark Matter and Dark Energy are different from Anti-Matter and Negative Energy (characterized by negative values.) The “Dark” stuff isn’t just “non-luminous,” it would have to be perfectly transparent, but with a great deal of mass. So that when a star passes behind a clump of Dark Matter, the Dark matter itself does not eclipse the observable star, but it’s gravitation is such that it can bend the star’s light to create a lensing effect. From the observation, all we can really say is, “because of THIS movement, we deduce that there must be something OVER THERE exerting a gravitational force.” But when we look there, all we can see is empty space, and the stars and galaxies behind it.
It is just as plausible that this effect is caused by microscopic black holes with a very small physical footprint, but a substantial mass and gravitation.
Without a baseline map of spacetime (which we don’t have) then the same lensing and gravitational effects we observe could be attributable to a looseness in the uniformity of the gravitational constant, and variability in the speed of light. While Einstein would not have liked this much, recent evidence suggests that neither the speed of light nor the gravitational constant of the universe are precisely fixed, as they have long been presumed to be.
Non-uniform density of spacetime itself could be all the explanation needed to understand the Canadian interpolations.
I’m not against the Dark Matter hypothesis, because until we really have more evidence, the jury is still out. But I do have a bit of an issue with people accepting Dark Matter and Energy as a fact, when there are so many paradoxical problems with it, and so little direct evidence of it.
Great replies W. Scott. I also had problems with the article. Isn’t Dark Matter a completely invisible, unobservable and exotic form of matter; whereas these maps can be made by objects lensed by more standard matter that is just invisible to us because it is not emitting enough light to be observed? Why should they automatically assume its “Dark matter”?
I also firmly believe that the answers lie in understanding higher dimensions and how they interact in the observable 3d world we live in. M-Theory seems to be leading the way.
There is zero evidence of multiple dimensions. Mathematically they are wonderful fun; in the real world there is no evidence for anything beyond 3 spatial and 1 time dimension. See the Wiki article.
But that doesn’t stop me from enjoying all the science fiction that uses multiple dimensions, including this article.
The distribution of dark matter obtained from a large numerical simulation at the Max-Planck Institute for Astrophysics bears an curious similarity to nuerological structure.
Maybe I am missing something, but how can we infer how light from beyond this supposed giant mass of dark matter is being affected by the dark matter itself?
Is the cloud moving in such a way that we can see it pass in front of a section of space that had earlier observed? If not what are the changes we are observing in the light from objects beyond the dark matter? I am confused….
Dear John Mendenhall,
I submit that quantum entanglement and quantum tunnelling are evidence supporting multiple dimensions.
Spontaneous quantum eruptions of paired particles in empty space is supporting evidence of multiple dimensions.
String Theory’s consistent Quantum Theory of Gravity works where the standard model never has. Supersymmetry eliminates Quantum Theory’s open-door-policy on spectacularly absurd particles like Tachyons.
A multidimensional universe, like dark matter, is still one hypothesis, unproven, but also like dark matter, has a statistically non-random positive distribution of supporting evidence, and an absence of directly conflicting evidence. Just because one scientist uses a telescope, and another uses mathematics doesn’t mean either has the superior approach to the truth.
Mathematically, cosmological theories including multiple dimensions are not simply wonderful fun, they are at the forefront of scientific understanding. Throughout history, theorhetical physicists have used mathematics to point the way, and the experimentation was years catching-up.
Newton, Einstein, Hawking, many many more, discovered in mathematical analyses things that it took researchers decades to establish with experimental observations.
But to my mind, Dark Matter is not an elegant theory, it’s a first shot in the dark at explaining something we should not be seeing by saying that something is there which can’t be seen. Something which is neither positive nor negative, and not zero. We’ve even had to invent whole new particles to try and explain it away. Never mind that none of these particles have ever been observed in any of the tens of thousands of particle interaction experiments we’ve ever conducted. So we need to add yet another hypothesis to explain why we’ve never detected anything like Dark Matter itself.
And I’m saying that if you run the observations through M-Theory’s supersymmetry, you get explanations rather than more anomalies, and we don’t have to come up with names for any new particles.
The rule in science is, keep it as long as it’s useful. The standard model is useful for many things, but we keep seeing the seams where our wrapping paper just doesn’t fit so neatly around the box. That doesn’t mean we have to throw it out, but it also doesn’t mean that we must limit science to only wht we can test right now. Mathematics opens doors to things we might be able to test a hundred years from now. And the sooner we start understanding what the possibilities are, and what they aren’t, the better we’ll know what we need to test, and how useful it will be.
I just deleted hundrets and thousands of words I had typed in here, and don’t really want to post anything more on the topic.
However, whoever is REALLY interested into the science, theory and practical research of dark matter and dark energy should look out for a series of lectures published on DVD by The Teaching Company, and lectured by Sean Carroll. It’s called “Dark Matter, Dark Energy – The Dark Side of the Universe” (TTC Video) and I can only recommend it, it’s not too cheap, but as always you can try torrents 😉 It’s 24x 30min, and after following these courses for one or two times, you will certainly be better off
@Kevin: The effect you described is caused by any massive object in the universe, and so it is by our own sun as well. During a solar eclipse it is dark enough to observe it: You can actually see stars and galaxies, that you shouldn’t be able to see, because they are right behind the sun. The sun is in the line of sight, and should be blocking the light coming in. But the gravitational field of the sun bends the incoming light around it, and we can see an object that is behind the sun as appearing next to it.
check out wikipedia for gravitational lensing, there even is an animation 😉
http://en.wikipedia.org/wiki/Gravitational_lensing
heh, just looked it up…
It was Sir Arthur Eddington who launched an expedition during a total eclipse of the sun in 1919, measuring the positions of distant objects in a certain part of the sky just normally, without the sun in the way, and also during the eclipse, with the sun in fromt of the objects.
They could prove that the observable postions of the objects had been shifted by the sun due to the gravitational lensing it produced by comparing the images and positions with and without the sun inbetween.
Einstein himself was the one who had predicted such an effect already in 1915. Luckily, shortly after this WW1 was over, and Eddington had the possibility, resources and perfect time to launch the expedition, and prove him right (I belive they went to South Africa)
(part 6 – “Gravitational Lensing” of the TTC course I mentioned above)
I understand what gravitational lensing is. Is this cloud of dark matter actually dense enough to act as a gravitational lens. I guess that wasn’t discussed in the article.
Hi Kevin,
The Canadian researchers looked at images of an apparently empty patch of sky as stars and galaxies passed behind it. They observed consistent lensing (by comparing the stars and galaxies to where they SHOULD be seen at any given time, or observing dual-images of the observed objects) caused, presumably, by gravitation that had no observable source. And that’s the crux of the issue.
Dark Matter cannot be a cloud in space. It allows light to pass through, and does not obstruct the passage of light in and of itself. A better name for it would be “invisible mass,” but the acronym “IM” was already taken. However, the idea is that this “exotic” mass is massive enough that it’s gravity can bend light. Now, this is admittedly profound, almost reminiscent of Copernicus’s crystal spheres upon which the stars of the firmament were suspended. And there is an enormous amount of science behind this. and the amount of the universe, in theory, occupied by this dark matter and equally enigmatic dark energy, is more than half the universe. If you think of it as black dust, it would obscure the vast majority of the visible object in the night’s sky.
But when we call it “Dark Matter,” we are making some shortcut presumptions which are not literally true. If it is a substance, which we have not established, then it directly violates the strict definition of matter. It is made up of nothing like any of the elements in the periodic table, even the mostly imaginary ones.
I am more than satisfied that we are observing something important, and that it’s effects are lensing artifacts and a relationship with matter and spacetime… but we don’t know enough to understand whether there is some invisible non-stuff squeezing everyting, or if the observations point toward another nuanced error in Newton’s equations. Newtonian physics works pretty well, but we know, from a few moonshots, that Newton’s equations are ever so slightly off.
But you see, they shouldn’t be. Their iron-clad assumptions are woven libreally through Einstein’s explanations, and Albert’s devotion to Newton made it impossible for him to grasp the Quantum Mechanics universe of Neils Bohr. Nothing in the standard model of three spatial dimensions plus one time dimension, combined with the observed evidence, is sufficient to establish dark matter as a reality, but also fails to explain what we see in telescopes.
The best answer now is, we don’t know what’s happening yet. We need to keep open minds, and explore ALL the possibilities.
So we should build a huge radio telescope array on Mars, and financially subsidize every mathematician/physicist on the planet.
Or we could live in the dark for another hundred years, for that matter.
And while I’m here… Kip Thorne for President.
Jovica Aleksik,
I’m too old and too broke to buy a series of discs that would cost more than auditing the best class in the field at Syracuse University.
But if you have studied the subject, do please give us an elegant and precise comparison of the implications of M-Theory and the problem of Dark matter. Oh Please!
I’d do it, but I once dropped-out of a calculus class, and my future as a cosmologist has gone downhill ever since.
Jeeeez people!
Dark Matter and Dark Energy are mainly used as general and catch-all terms in astronomy. They are used to describe, in the broadest possible terms, something that exists that causes a corresponding effect.
Dark matter is the term that refers, in the broadest possible terms, to the implied cause of an observed effect. Namely, the effect that the magnitude of the gravitational force in most parts of the Universe appears to be greater than what we can account for by adding up the contributions from all of the observable matter that we know about.
Likewise, in a Universe whose expansion is apparently accelerating, our current understanding of gravity demands that there be a cause of this acceleration. The cause is termed ‘dark energy’, because it needs a name and nobody knows for sure what it might be.
Many scientists have proposed specific phenomena as being the answer to DM and DE – the theories are out there, and now we await the observations that will either cut them down or lend them credibility. But lets just remember that, in broad terms, the terms DM and DE are really just names for gaps in our current understanding… In this respect, there is nothing really wrong at all with the original article.
W. Scott –
Your postings are most informative and well considered. “We need to keep open minds, and explore ALL the possibilities” is so relevent in matters of cosmology. That said, I would like to acknowledge Jovica Aleksik’s reference to “Dark Matter, Dark Energy” DVD course from The Teaching Company. Yes – a bit pricey (you can get the package during one of their frequent sales) but I could not stop watching the entire course, almost at one sitting! Sean Carroll from Cal Tech did the presentation. I can not do the material justice here (or anywhere else for that matter) but the thread that I got from Dr. Carroll’s class was his openess to “ALL the possibilities” – including M-theory, string theory, and branes etc.
My copy of “DM, DE” is on loan to a friend now. I wish the public library would have a copy available for those so interested. Until then, good mentors like youself and others will continue to presnt us with “ALL possiblities.”
“W. Scott Says:
February 25th, 2008 at 12:45 pm
Dear John Mendenhall,
I submit that quantum entanglement and quantum tunnelling are evidence supporting multiple dimensions.
Spontaneous quantum eruptions of paired particles in empty space is supporting evidence of multiple dimensions.
String Theory’s consistent Quantum Theory of Gravity works where the standard model never has. Supersymmetry eliminates Quantum Theory’s open-door-policy on spectacularly absurd particles like Tachyons.
A multidimensional universe, like dark matter, is still one hypothesis, unproven, but also like dark matter, has a statistically non-random positive distribution of supporting evidence, and an absence of directly conflicting evidence. Just because one scientist uses a telescope, and another uses mathematics doesn’t mean either has the superior approach to the truth.”
You miss the point. There is no observational evidence to support more than 3 space and 1 time dimension. It is a great disappointment; we casually bandy about the idea of multiple dimensions all the time, and it becomes part of our way of thinking. But the best research finds no physical evidence of multiple dimensions. Believe me, I was shocked to find this out. The real universe cold, cruel, and simple. One, two, three, and it only moves in one direction in the fourth.
The quantum phenomena are not evidence of multiple dimensions, they are predicted as events with a non-zero probablity. The string theories, as we all know, have not yet made any testable predictions. SR and GR make and have made many, many testable predictions, using 4-space, and have passed them all with flying colors.
i believe dark matter is matter not yet discovered;dark energy seems to have better explanations.
To Jovica Aleksik,
“Neutrinos and black holes have nothing to do with dark matter.”
I don’t think you know what you’re talking about here. Dark matter is merely matter that does not emit any form of electromagnetic radiation. Because the matter in black holes does not emit light, you can say it is in fact dark matter.
Another good set of postings, Guys!
I agree with with W Scott & Astrofiend, in the sense that there seems to be some confusion as to what Dark Matter & Energy actually ARE, what scientist mean when they use these terms & what the rest of the (non)-Scienctific community mean.
What was taken as a shorthand to describe effects that couldn’t be readily explained has taken a life of it’s own beyond the original meaning, especially in a sound-bite culture
very interesting talkback. i’m not smart enough to comprehend the math behind M-theory and the current debate over the existence of dark matter, but one thing seems clear: that we are at a kind of impasse. sounds like physicists and cosmologists are struggling greatly to come up with a theory that explains how the universe continues to expand, but nothing anyone’s come up with so far is testable.
the universe is keeping its mysteries for now.
it would be very interesting to me if we eventually discovered that the speed of life and force of gravity were in fact not uniform throughout the universe.
how strange and intriguing this all is to ponder. sometimes i look at the sun and can’t believe it ever even formed.
i meant ‘speed of light’. a nice slip.
Heh, I was already trying to imagine a meaning for “speed of life” 😀 indeed a nice one..
About the non-testable predictions of String Theory: Let’s wait a year or so.. The Large Hadron Collider at CERN is only about to begin operation.. There might be some interesting new observations at the energy levels it will reach. Maybe there won’t be any surprises at all, but I definitely doubt that 😉
Some good criticism being formulated about this article.
One wonders what individual is capable of writing something as asinine and wrong as “It is well documented that dark matter makes up the majority of the mass in our universe. The big problem comes when trying to prove dark matter really is out there” If it is so well documented why is it difficult to prove?
If “It is dark, and therefore cannot be seen” why does the title say “Dark Matter Web Structures observed”.
And this gets published!!!!
Forget about trying to find real dark matter.
My hypothesis shows how real visible matter
can mimic the so called dark matter. Read my
idea at my website:
cosmicdarkmatter.com
W. Scott, I lift my hat to you, sir.
While the original article left me dubious on its validity and scientific value, your replies and those of others above really got me thinking… and left me lost in their wake.
As a casual observer of the cosmological and astrophysical scene, as well as an avid reader of Universe Today, all this left me more confused than ever. And even more skeptical about the scientific interest of the articles presented herein. I’m not too sure anymore of what credibility I should attribute to UT !
Thanks (sort of, lol) 😉