Slashdot Mirror
Dark Matter Exists
olclops writes "It's a big day for astrophysics. After much speculation, scientists now have conclusive proof of dark matter. This result doesn't rule out alternate gravity theories like MOND, but it does mean those theories will have to account for exotic forms of dark matter."
The announcement of the pending announcement regarding Dark Matter
I guess he's never heard of Zaphod Beeblebrox.
"A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists."
Also a bit of info on physorg
How does the Coalsack Nebula fit into this? It's dark and it's matter, right?
A feeling of having made the same mistake before: Deja Foobar
...the server must have known of the impending slashdot effect and preemptively protected it's CPU from the impending meltdown
A black hole is where God divided by 0
Starship fuel! And... if dark matter exists... then something must exist to have created the dark matter... Onward, to Vergon 6!
Show this to your friends and family that don't know what a real hacker is
Proof is a big word and Dark Matter is a very silly theory, I want it in the lab before I accept somthing THAT unlikely!
Buy Steampunk Clothing Online!
How does this effect the Stargate program?
bluespaceradio.com - New Wave, Indie and Alternative
Here's some info from NASA.
Post-rock/Ambient/Drone and other noise.
It's a big day for astrophysics.
This Account Has Exceeded Its CPU Quota
I think it's going to be a big day for their webmasters as well.
Now it's our turn to hide from the dark matter and wait for it to discover us! Come one everyone - pick a hiding spot and get to it! Hurry!
Hexy - a strategy game for iPhone/iPod Touch
Funny, I always figured the announcement of experimental confirmation of dark matter would first be published in a scientific journal or announced at a news conference...not on a blog shared by Mark, Claire, and Sean, whoever they may be.
* Note that I tried to go back and confirm the names and finish reading the story so I would have something intelligent to say, but apparently the user's CPU allottment only accounts for 20% of the server's total, suggesting that there may be another form of CPU cycles that don't interact with visitor's to the linked site. I think we should call these "dark CPU cycles."
The full paper can be found here. From the abstract:
We present new weak lensing observations of 1E0657558 (z = 0:296), a unique cluster merger, that enable a direct detection of dark matter, independent of assumptions regarding the nature of the gravitational force law. Due to the collision of two clusters, the dissipationless stellar component and the fluid-like X-ray emitting plasma are spatially segregated. By using both wide-field ground based images and HST/ACS images of the cluster cores, we create gravitational lensing maps which show that the gravitational potential does not trace the plasma distribution, the dominant baryonic mass component, but rather approximately traces the distribution of galaxies. An 8 sigma significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law, and thus proves that the majority of the matter in the system is unseen.
does this mean grey matter exists as well?
http://chandra.harvard.edu/photo/2006/1e0657/
For those who prefer here are the salient links which TF"A" (it's a blog entry) is referencing: http://chandra.harvard.edu/chronicle/0306/devil/ http://chandra.harvard.edu/press/06_releases/press _082106.html
Caveat Utilitor
It's in space, though. And according to all of our data, it is also gay. Please see our website for more information: http://www.gnaa.us/
Dark water, flush twice.
I, for one, welcome our...
:wq
After much speculation, scientists now have conclusive proof of dark matter.
Well, their proof is based on the detection of gravity and gravitational fields. Every real American knows that it's not "gravity", but "intelligent falling". Gravity is a myth invented by foreign scientists to make all Americans seem overweight.
The theory of relativity doesn't work right in Arkansas.
Astronomers observed a distant cluster of galaxies in optical light, with ordinary telescopes, and in X-ray light, with a telescope in space. This is an unusual cluster of galaxies, since there is clear evidence that one small group of galaxies are "interlopers:" members of a smaller cluster which fell into a larger one some time ago. Members of this interloping group are all bunched together at one side of the main cluster.
The visible light image shows the galaxies within the cluster. It also shows, much fainter and much smaller, a very large number of BACKGROUND galaxies -- these are objects way, way farther away than the big cluster. As the light from these background galaxies passes through the big cluster, it is bent very slightly by the gravitational field of the cluster. This gravitational lensing distorts the shapes of the faint, little background galaxies just a bit, but with care, we can measure the effect. We learn from the lensing where the matter is in the cluster: that is, we can figure out where the stuff which produces gravitational effects is distributed. That's part one: a map of the matter within the cluster, based on gravitional lensing.
The X-ray image shows emission from hot gas within the cluster. We have known for several decades now that large clusters of galaxies are immersed in giant clouds of very hot gas, at temperatures of millions of degrees. The gas emits copious amounts of X-rays. In most clusters, the amount of this hot gas -- its total mass -- is much larger than the amount of mass we can see in stars. That is, counting the stars in the galaxies suggests a total amount of mass-in-stars M, but computing the amount of hot gas necessary to emit all the observed X-rays yields a mass-in-hot-gas of around 10*M, ten times as much.
On the other hand, the amount of mass derived from the gravitational lensing of background galaxies is about 10 times larger still, or about 100*M. The stuff which produces the gravitational lensing does not emit visible light, nor X-ray light, nor, as far as we can tell, any electromagnetic radiation. Therefore, we call it "dark matter". It produces a gravitational force, but that's about all we know about it. (There are additional reasons for believing that this mysterious stuff is not made up of electrons, protons and neutrons, but that's another story).
This new result is interesting for this reason: the X-rays appear on one region of the cluster of galaxies, telling us that the bulk of the ordinary matter is RIGHT HERE. The map of total mass we can make from gravitational lensing appears in a different region of the cluster, telling us that the bulk of the dark matter is OVER THERE. It is very clear that the dark matter and ordinary matter are distributed in different places. This isn't too surprising, perhaps, if one small group of galaxies rammed into a big cluster -- the gas ram pressure might push on the ordinary hot gas in a different way than on the dark matter (which wouldn't feel any ram pressure at all, actually).
As Martin Hardcastle pointed out to me in a Google newsgroup a few days ago (thanks, Martin!), this is certainly not the first evidence for dark matter -- we have a number of examples in which gravitational forces are larger than the amount of visible matter would suggest -- but it is the first good case in which the distribution of the dark and ordinary matters are so clearly displaced.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
...just supposition. After reading all this, all I see is that dark matter, which cannot be observed by any means other than gravitational effects on other non-dark-matter matter and seems suspiciously absent from everyday experience and experiment here on Earth, must exist because we think we see mass and energy behaving in a way that goes with our theories, yet we've seen it behave that way before and it is only in recent times we've decided that something is wrong with physics and we need dark matter.
Can anyone say aether? I knew you'd try...
We have next to zero understanding of the quantum vacuum, and don't know for certain if everything should pop in and out there including not only electrons and photons, but antiprotons and neutral pi mesons and everything else too. We do know it exists from many many Earth-side experiments and reams of dead trees covered in equations. We don't know how the potential fields exist which give rise to the fields we know, we don't know how any of them link in all ways to the nuclear fields which we also don't understand too well but we have loads of equations and experiments for those.
So we invent something, call it "dark matter", and look for anything we can then say matches our thought experiments and we can forgo all the careful Earth-side experiments. We just sort of treat the absence of any dark matter here or anywhere near here as one of those Hitchhiker's Guide SEPs.
More science-by-supposition and proof-by-spectacle. Show me the proof. Show me why dark matter has to exist. Prove it out with careful calculation and application to everything across the board. We've set off fifty megaton nukes for crying out loud without a single sign of anything amiss that would suggest we have a giant hole in physics requiring dark matter. We've done experiments on electromagnetic fundamentals, nuclear forces, and so on and along the way, we didn't hear of a need to invent dark matter.
But some people look at the cosmos and decide that despite not truly understanding the whole picture of physics at every scale yet, we can claim that dark matter exists and here's proof. Where in the Nine Hells does this stuff fit with the physics theories they alread promulgate as accepted science to be taught in universities?
It looks like modern aether, and it looks as though anyone buying it will be upset when someone working right along on the regular investigations into quantum physics and spacetime and so on puts it together and says, "oh, here's why that galaxy moves that way. We didn't need dark matter after all..."
If my grammar and spelling are off, I am [distracted/tired/careless] (take your pick)
I had read that if the universe were infinite that the sky would be blindingly white from all the old light from old stars, which is one of the reasons that a Big Bang (or other creation) was assumed to have happened.
But if there are dark clouds that can absorb the light, could there be stars further than 13ish billion light years away, that are simply obscured?
Less bad about the Dark Matter futures I purchased when GOOG hit $87.
This Account Has Exceeded Its CPU Quota
I haven't yet read this article due to it being slashdotted, but I'm sure it is at least as credible as the story about the new source of free energy from magnets and as accurate as the one that says goldfish are smarter than dolphins.
1 voice in a sea of voices
Storm
Did they get any pictures of Nibbler?
And a scant few minutes later... SLASHDOTTED
TRealFA: here (the dark matter bragging) and here (details on the lensing observations). Perhaps certain folks will take the time to read and understand them before blathering about "fudge factors" and "modern ether". But probably not.
We know nothing, and yet you can post bitchy comments to slashdot, on a computer, connected to the Internet, powered by a physical plant hundreds or thousands of miles away piping electricity directly into your laptop, and then watch a show on TV over cable distributed by satellite.
I'd hazard a guess that we actually do know a thing or two.
Anyone who loves or hates any language, platform, or manufacturer, doesn't know what they're talking about.
that the night sky is not the temp of the suns surface is called olbers paradox http://jersey.uoregon.edu/~imamura/123/lecture-5/o lbers.html.
I believe the resoluiton of this paradox is one of hte outstanding successes of the expanding universe idea discoverd by hubble
i really good comment to 100 wiseass stupid comments - pretty goood for /.
Can you comment on whether the data support a candidate such as wimps, machos, etc ? (or am I betraying my ignorance with these acronyms
AP: On August 21st, 2006, three scientists who claimed the extrordinary proof of the discovery of dark matter were sued by an Irish company, Steorn, for patent infringement and copyright violation, following the company's announcement of technology to produce 'free energy.' American Physicist Josiah Willard Gibbs could not be reached for comment.
We know nothing,
Correct.
on a computer, connected to the Internet, powered by a physical plant hundreds or thousands of miles away
Oh yeah. Computers. The pinnacle of human knowledge. Right before the cursor freezes.
We know a thing or two, but we can't feed everyone. We have satellites orbiting the Earth while people live on sidewalks.
We know nothing.
Business isn't willing to pay for products, innovation and careers, so we get brands, mortgage commercials and layoffs.
George Bush hates dark matter
This data provides no evidence for the makeup of the dark matter.
Other observations suggest that the dark matter is not Massive Compact (Halo) Objects, or MACHOs. The idea that dark matter might be composed of some sort of Weaking Interacting Massive Particle, or WIMP, is a bit out of fashion these days, but still a possibility, as far as I know.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
From the title - "This result doesn't rule out alternate gravity theories like MOND". Actually, this directly rules out MOND. That's a big part of the point of the experiment.The idea is that the mass in these clusters doesn't come from the obvious sources of visible matter (the gas), as it would in a MOND or normal gravity scenario, but rather from the invisible (i.e., dark) matter.
the PP is correct, before anyone jumps off and gets on his case, as has happened before.
... well, nearly always! [...]
From Dictionary.com
Effect
tr.v. effected, effecting, effects
1. To bring into existence.
2. To produce as a result.
3. To bring about. See Usage Note at affect1.
(e.g. "The Senator was afraid that the new policy would effect higher oil prices.")
Also, effect is often seen as a noun, meaning (among other things) a result. For example: "The Senator was afraid that the new policy would have detrimental effects on the oil industry."
On the other hand:
Affect
tr.v. affected, affecting, affects
1. To have an influence on or effect a change in: Inflation affects the buying power of the dollar.
2. To act on the emotions of; touch or move.
3. To attack or infect, as a disease: Rheumatic fever can affect the heart.
(e.g. "The Senator was afraid that the new policy would adversely affect the oil prices, dragging them higher.")
Affect is rarely used as a noun, although it is much more commonly seen as a verb. Affect as a verb: "The man had a strange brand of body language that lent him an odd affect."
If you don't believe me:
Usage note from dictionary.com:
"Usage Note: Affect and effect have no senses in common. As a verb affect is most commonly used in the sense of "to influence" (how smoking affects health). Effect means "to bring about or execute": layoffs designed to effect savings. Thus the sentence These measures may affect savings could imply that the measures may reduce savings that have already been realized, whereas These measures may effect savings implies that the measures will cause new savings to come about."
Usage note from wikipedia.com:
"Do not confuse affect with effect. The former is used to convey the influence over existing ideas, emotions and entities; the latter indicates the manifestation of new or original ideas or entities. For example, "...new governing coalitions during these realigning periods have EFFECTED major changes in governmental institutions" indicates that major changes were made as a result of new governing coalitions, while "...new governing coalitions during these realigning periods have AFFECTED major changes in governmental institutions" indicates that before new governing coalitions, major changes were in place, and that the new governing coalitions had some influence over these existing changes."
Usage note from Write101.com:
"The easiest way to distinguish the two is to remember that affect is a verb (well, nearly always a verb) and effect is a noun
When affect is pronounced [uh FEKT] and accented on the final syllable, it's a verb meaning "to have an influence on."
eg Nothing they did, could affect my decision to go to the beach.
Occasionally, very occasionally, the word is used as a noun (it means a feeling or emotion, as distinguished from thought or action, or a strong feeling having active consequences) and the accent is on the first syllable [AFF ekt]. This is a term that is reserved for psychiatry and psychology:
eg In hysteria, the affect is sometimes entirely dissociated, sometimes transferred to another than the original idea.
Effect is most usually a noun and it means the result of some action or the power to produce a result. The noun is pronounced [uh FEKT] :
eg The effect of the bushfire was clearly visible.
eg The soothing music had an immediate effect on the wild beast.
This can also be a verb and it means to bring into existence, to produce a result (pronounced [ee FEKT]}"
http://www.TheGamerNation.com/Forums
Or, er, rather dark matter ate their server.
...Er, much like this post.
This suggests that dark matter may not only be dark in terms of information, but also dark in terms of disposition, ie, evil; eg Doctor Who telling off Satan in the "timeless space between worlds."
Ahem.
Dark matter has a bad attitude. That's the bottom line. It isn't seen because it doesn't want to be seen.
I suggest we all make offerings and sing around a dark matter-shaped totem, with fire and sacred wine. Ask yourself: what has good-side-of-the-force matter done for you lately? Nothing, that's what. It's time to demand a matter that delivers on the promise of nothing.
These stories are free but worth money.
You are assuming that with knowledge comes compassion which isn't correct. We could house everyone, however, housing everyone where they want with the conditions they want is a different matter.
There is no proof without some dark matter to examine.
in soviet russia, dark matter discovers you!
(sorry...)
Someone discovered the existance of Vergon 6
You generally can't prove a physical theory, because you're not sure that the theory will hold in the future or under circumstances you didn't measure.
:)
A better headline would be, "Dark Matter once again not disproven."
We know a thing or two, but we can't feed everyone. We have satellites orbiting the Earth while people live on sidewalks.
What are you going to do about it? Give arbitrary power to somebody, who will feed and house the poor with the wealth of the rich? You think some form of collectivism wouldn't quickly degenerate into totalitarianism?
We are what we are. We can only build on what we have previously done. There is no magic of the gods that will allow us to become a species of greater beings; that only happens through the analysis and synthesis of our environment and our own imaginations.
Please keep in mind that even the best of us have flaws, and that the worst have many, many more.
all this Dark Fiberthat they talk about really exists, 'cause I'm still stuck on dial-up :-(
Since the Irish company Steorn figured out free energy thay have yet to figure out it creates dark matter
Or that its really not breaking the laws of physics.
There's no point trying to tell you how much we do know, Debbie Downer, because you're determined to hate humanity and life and existence because [God says so | I'm emo and I hate myself | My life sucks and I want yours to suck too].
But just to drop a few clue-by-fours: Wrong, (the majority of computers on earth, those used in cars, will run correctly forever except for a hardware fault), wrong (the United States alone grows enough food to feed 2.4 billion people, even after wasting so much on feeding cattle), and irrelevant (the social conditions which create and drive poverty have nothing to do with artificial satellites).
Remember Vulcan, the planet with an orbit inside of Mercury? It was PROVEN to exist in the late 1800s. The calculations showed that Mercury's orbit required a smaller planet to make Mercury's orbit precess as it did. People even went looking for it with the finest telescopes of the day. And they saw it.
Then some smart aleck who worked in a patent office came along and showed that space is warped and that Mercury's orbit fits perfectly. Vulcan disappeared, never to be seen again.
Vulcan had more data in favor of its existence back then than dark matter does now. Pardon me, but I'm as skeptical as parent.
...free energy then this is all completely irrelevant. All of the computations for any of the dark matter or MOND models assume that energy is conserved. If energy isn't conserved then galaxies can do whatever the hell they like - spin this way and that, jump up and down and form themselves into obscene words for the benefit of astronomers peering through telescopes. Well, maybe not that bad, but questions about the rotation curve of galaxies kinda become moot.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
Definately a discovery to celebrate over drinks. Where's the keg party? Better yet, break out the whiskey and let's light some cigars instead. I knew there was dark matter ... why else is the night sky black with so many damn stars out there?
There is an infinite amount of knowledge (when we learn new things, we are presented with new questions), but only a finite amount of things that we can know. Of course our knowledge is incomplete. It always will be.
That does not mean we shouldn't try to learn as much as possible, however. What we have accomplished is far beyond what any other animal on earth has done.
The proof is clearly in the pudding. If you recall from science class, the pudding itself is expanding but raisins are not. Consequently, redshift.
These stories are free but worth money.
From the NASA press release: "These results are being published in an upcoming issue of The Astrophysical Journal Letters."
Two points. First, journals really hate it when press releases are made prior to the publication date. Second, this journal has an "impact factor" of ~5-6, compared to Nature, or Science, which have impact factors of ~25. Why are they publishing in some obscure journal if this is really the rock-solid proof that they claim it is?? Makes me wonder.
as soon as I saw the picture:
e r.gif
http://www.cellarator.com/images/black-space-larg
Or maybe Dark-Brown Matter, or Gray Matter, or possibly Doesn't Matter. ;-)
"My strength is as the strength of ten men, for I am wired to the eyeballs on espresso."
"we know nothing"
A mistake known as "generalising from self"; you know nothing, therefore you assume that everybody else must know nothing too (not your fault, you cannot conceive of anything else). This is a primitive form of reasoning called "induction", whilst it can have its place, it often leads to huge inaccuracies such as deriving "we know nothing" from "I know nothing".
Proof of your limited ability to use logic:
"we know nothing, and what we do know..."
The two are mutually exclusive; we cannot both know nothing, and have stuff that we do know.
Proof of your lack of knowledge:
"Science-is-infallible types claim to know and understand the universe"
No they don't. They claim to be trying.
With both a lack of knowledge and a lack of ability to use logic, one might think the two would cancel out and you'd get a thing or two right, but I guess you're pretty unlucky, which would explain the bitterness too.
The revolution will not be televised... but it will have a page on Wikipedia
..does it matter?
I have a basic question:
Can this "dark matter" be regular matter that is just not well lit, or does it have to be some new kind of elemental particle as much of the discussion here seems to imply?
Since the only things we can see out there are stars and things close enough to them to be lit by them, I would assume there can be enormous amounts of other things in space that we just don't see. Think a trillion earths, and/or huge thin gas clouds. But it sounds like that's not what's being discussed here.
Your statements prove that we don't know EVERYTHING. That is not the same as proving we don't know anything.
Three days from now?? Thats tomorrow!! ~Peter Griffin
A steaming pile of Dark Matter was found on the sidewalk and traced back to Nibbler's litterbox. Bad Nibbler!
It must have been something you assimilated. . . .
Maybe it's not dark matter at all and more like reflected matter. Just how light is refracted.
Did anyone else notice the amazing quality of TFA? I actually understand more about dark matter from that article than from anything else I have read on the subject to date. This makes me less grumpy about all the money I felt was "wasted" on telescopes vs. planetary exploration.
Quidquid latine dictum sit, altum viditur.
If MONO is dead, we will have no choice but to run our beloved C# code on Microsoft platforms!
Wait... incoming news... that's MOND, not MONO.
<Squeeky Voice> Nevermind. </Squeeky Voice>
This issue is a bit more complicated than you think.
Show me some dolphins that can do this.
This appears to be no more a confirmation for dark matter than when the Michelson-Morley experiment (in 1881) "confirmed" the existence of ether. In the immediate aftermath of the Michelson-Morley experiment, theoreticians generated lots of mathematical "proofs" (e.g., The Ether of Space, Sir Oliver Lodge, Harper & Bros, 1909) that showed how a boundary layer in the ether surrounding the Earth accounted for the observed results. A series of subsequent refinements of the Michelson-Morley experiment showed that the speed of light was truly independent of direction, and Einstein's theories, which did not require the existence of ether, provided a better fit for the observed results than was a boundary layer in the ether.
Over time, the Michelson-Morley experiment was recognized to have disproved the existence of ether -- but it wasn't that way initially.
Alternative explanations include "quantum critical phase transitions", and I'm sure that there are other possibilities, that a series of observations of similar cosmological events will provide the range of data needed to select the hypothesis that best describes the observations.
Being able to fudge one theory to fit a single observation falls quite a bit short of a "conclusive proof". Maybe dark matter does exist, but it's going to take a lot more observations for it to be convincing to me.
How precisely does dark matter permit the expansion of the universe to be defined, and how precisely does the observed phenomenon fit those numbers?
Wake me up when someone has a quantum mechanical model that tells how quarks are bound together in dark matter, or when someone manages to tap into dark energy (which is supposedly all around us).
You stand on the backs of legions of incredible people who spent their lives enriching everyone else's, and piss all over them because the world isn't perfect yet.
How fucking pathetic.
Anyone who loves or hates any language, platform, or manufacturer, doesn't know what they're talking about.
The Combine are coming, start hoarding canned goods!
*runs*
The last time I checked, emperical observation provided confirmation of theories, not proof. Proofs are what you get in mathematics.
Looking for an 'informative' answer :)
...they aren't bashed enough! The damn things are still multiplying.
Sean at 11:52 am, August 21st, 2006
The great accomplishment of late-twentieth-century cosmology was putting together a complete inventory of the universe. We can tell a story that fits all the known data, in which ordinary matter (every particle ever detected in any experiment) constitutes only about 5% of the energy of the universe, with 25% being dark matter and 70% being dark energy. The challenge for early-twentyfirst-century cosmology will actually be to understand the nature of these mysterious dark components. A beautiful new result illuminating (if you will) the dark matter in galaxy cluster 1E 0657-56 is an important step in this direction. (Heres the press release, and an article in the Chandra Chronicles.)
A prerequisite to understanding the dark sector is to make sure we are on the right track. Can we be sure that we havent been fooled into believing in dark matter and dark energy? After all, we only infer their existence from detecting their gravitational fields; stronger-than-expected gravity in galaxies and clusters leads us to posit dark matter, while the acceleration of the universe (and the overall geometry of space) leads us to posit dark energy. Could it perhaps be that gravity is modified on the enormous distance scales characteristic of these phenomena? Einsteins general theory of relativity does a great job of accounting for the behavior of gravity in the Solar System and astrophysical systems like the binary pulsar, but might it be breaking down over larger distances?
A departure from general relativity on very large scales isnt what one would expect on general principles. In most physical theories that we know and love, modifications are expected to arise on small scales (higher energies), while larger scales should behave themselves. But, we have to keep an open mind in principle, its absolutely possible that gravity could be modified, and its worth taking seriously.
Furthermore, it would be really cool. Personally, I would prefer to explain cosmological dynamics using modified gravity instead of dark matter and dark energy, just because it would tell us something qualitatively different about how physics works. (And Vera Rubin agrees.) We would all love to out-Einstein Einstein by coming up with a better theory of gravity. But our job isnt to express preferences, its to suggest hypotheses and then go out and test them.
The problem is, how do you test an idea as vague as modifying general relativity? You can imagine testing specific proposals for how gravity should be modified, like Milgroms MOND, but in more general terms we might worry that any observations could be explained by some modification of gravity.
But its not quite so bad there are reasonable features that any respectable modification of general relativity ought to have. Specifically, we expect that the gravitational force should point in the direction of its source, not off at some bizarrely skewed angle. So if we imagine doing away with dark matter, we can safely predict that gravity always be pointing in the direction of the ordinary matter. Thats interesting but not immediately helpful, since its natural to expect that the ordinary matter and dark matter cluster in the same locations; even if there is dark matter, its no surprise to find the gravitational field pointing toward the visible matter as well.
What we really want is to ta
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
Isn't it great that a contoversial issue such as this has been proven and published as existing on a blog written by theorists?
Relax everybody & wait for the results to tricle out and digest. In the mean time, how about a nice tall freshing drink of Gelfling Essence?
Original NASA article/ dark_matter_proven.html
http://www.nasa.gov/vision/universe/starsgalaxies
John Baez (physicist who have a lot of fun staff on his homepage) more coherent explanation
http://math.ucr.edu/home/baez/week238.html
...is a way to make bibles that release contraceptives into the systems of those who thump them.
My understanding is that gravitational lensing here suggests that dark matter hangs out around "cold matter" or solid matter, like stars and planets, but not "hot matter" like plasma. Why would the mysterious dark matter only stay with the solid matter? What theory of dark matter predicts that it ignores plasma? Am I missing something?
Table-ized A.I.
Seeing this discovery, this would also imply that the universe is either contracting to a single point or remaining in its current state.
This should probably put one scenario to rest, that of the open universe in which planets and galaxies (and individual atoms for that matter!) drift farther and farther out from each other, until virtual nothingness.
I am not an astrophysicist, happy to hear their opinion on this ?
Slashdot: stuff for news, nerds that matter, matter for news, stuff that nerd
I mean come on... if their initial assumptions are correct and the observed current mass distribution is correct and the calculations of how a gigantic collision would behave is correct and there was dark matter there then the results might indicate it was actually dark matter that did it. Needless to say it's completely untestable.
Matter that only interacts with normal matter through gravity... or maybe dark matter is gravity? Maybe gravity is similar to sound where an approaching body would appear to have higher mass as the compressed gravity waves 'pitch' is increased while a retreating one appears to have less gravity. Then instead of dark matter they could be observing something like a gravity shock wave. Or maybe space takes 'time' to 'deform' so an object in motion has a steeper curve ahead of it than behind (or vice versa). I mean who knows. It could be so many things.
Ok I know most astronomers are honest, smart, and highly educated. But how many times do we need to hear that the universe changed its age? Have they even ruled out that we aren't in some wrapping universe, toroid style?
There are two things at work here: one, there is much more dark matter than normal matter so the normal matter is actually hanging out with the dark matter rather than the other way around and two, the dark matter is very weakly interacting; especially with the very low density X-ray plasma.
I'll believe it when I see it.
Luckily we can't feed everyone. Otherwise we would have twice as much people next year.
Solving world hunger comes with a price. Would you accept forced birth control if it solves the issue of famine?
I can't tell which is the joke, the post or the moderation.
Actually I think particle physicists are happy there's all this exotic unknown matter floating out there. Most modern particle theories practically scream for there to be (as of yet undiscovered) supersymmetric partners of all known particles. If dark matter turns out to be SUSY particles that would be a great experimental confirmation. If I had to bet, that would be my guess as to what dark matter will turn out to be. The great thing about science is there's always something unexpected around the corner, it would be really boring if we knew everything already.
it reeks of PR. ... the kind of PR that happens when people are REALLY trying to get others accept a point that is hard to accept.
I've been following the "dark" story on and off since I stopped studying physics seriously after college. The MOND system makes a whole lot of sense. My non-professional-physicist read on the MOND / DARK controversy is that several of the alternate theories (like MOND) that remove the need for dark matter are fairly convincing. Dark matter is not convincing at all - not testable, not observable, and reminds me a lot of Santa Claus. Somebody brought the presents, right? The problem is that a vast majority of cosmologists are all so far down the dark matter band wagon that if dark matter goes away... lots of careers will be lost. Destroyed. These professionals who trade solely in reputation and intellectual-ism will have their rug pulled right out from under them.
A much more plausible explanation is that some people are trying really hard to amp up the PR. Sort of like what happens when you need a distraction from a big debate, so you get all the airline travelers to throw away liquids. Anyone who tells you they have proof for something that by definition can not be observed is selling PR. For those of you who believe it without question, I've got a bridge I'll sell you.
After taking about 30 minutes and reading no less than 6 heavily biased PR pieces... I say this stinks. It's certainly not science - (yet).
I've looked at all the animations, etc and all maps of the collision are in 2D. Would it be possible to create 3D volumes of the galaxy clusters and animate them as the dark matter and baryonic matter collide?
So what's new then? All along the whole case for "dark matter" was that galaxies -- _all_ galaxies -- rotate strangely like a rigid body, except right near the centre. According to newtonian mechanics the stars in a galaxy should behave basically like the planets in our solar system: the farther from the centre you get, the slower they move. But in a galaxy stuff moves like that only near the centre, and then it's like gravity changed gradually from 1/(R*R) to 1/R, and the stars rotate at an almost constant angular velocity around the centre.
;)
So from there it's that either:
1. there's a metric buttload of matter we can't observe other than through gravity, in some weird distribution all through the galaxy's disc, or 2
2. we accept that gravity isn't working like we think it does
(Or my favourite: 3. galaxies are just a rotating texture there, so _of_ _course_ they rotate like a rigid. Noone would be dumb enough to simulate the individual stars just to give us a pretty sky in this MMO we call RL
And somehow the favourite is 1, for no obvious reason than that noone wants to modify gravity theories. It's as if Galileo, upon discovering that a stone dropped from the mast doesn't lag behind the ship, would then proceed to invent some "dark wind" that pushes the stone along with the ship. Since existing wind obviously isn't strong enough to push the stone that hard, it's got to be some dark wind in there too. Just, you know, for the sake of not contradicting the existing Aristotelian system.
Anyway, all along we knew that it can't be conventional matter, because we already had plenty of galaxies in various states of illumination and they all behave the same.
So exactly how does the new one help there? It seems to me like it still can't offer conclusive proof that 1 is true and 2 is false, because it would _still_ be equally well explained by 2. What this "solves" is at most a sub-distinction inside 1, once we're dead-set on believing 1 instead of 2. It says basically that if we already decided it's 1, then, yep, it's definitely not baryon matter (rocks, gases, protons, etc), but some weird matter that interacts only with gravity.
A polar bear is a cartesian bear after a coordinate transform.
Take a gander at the published paper. A large part of the reason that this galaxy cluster in particular was chosen was because it is one of the cases known where we have a clear-cut idea of what's going on.
Their initial assumption (page 1 right column): "During a collision of two clusters, galaxies behave as collisionless particles, while the fluid-like X-ray emitting intracluster plasma experiences ram pressure. Therefore, in the course of a cluster collision, galaxies spatially decouple from the plasma." Since the area occupied by dense matter (stars) is more than 10^11 times smaller than that of the whole cluster, literally one or two stars might impact each other. Meanwhile, the intracluster gas is, however diffuse, GAS - it can't pass through itself, and is observed to contain ~80-90% of a cluster's visible mass.
I don't know the specifics of how this is done, but they used a gradient of the change in a background galaxy's size and related it to the curvature of space (and hence amount of mass). By plotting a lot of background galaxies, they were able to integrate the gradient to find the center of mass (warning: not 100% sure of this explanation) that was causing the lensing (green gradient lines on page 2).
When this is compared with an x-ray image of the gas which is known to comprise most of the visible mass of clusters, the two mismatch by about 6 arc seconds. On page 4, they discuss the probability of other clusters creating the apparent mass (1/10 million chance) or entire filaments of intergalactic mass creating it (1 in 100 million). The only remaining conclusion from this is that something which fits the description of dark matter (in that it has mass but no other measurable property) makes up the great majority of the cluster's mass and the two clouds of it passed through each other like the galaxies.
So, they expected the stars/dark matter and the gas of colliding clusters to separate in a collision, and this is exactly what was observed
deductive logic. The alternative to deductive logic is called inductive logic (basically reasoning with uncertainty), and that is what physics and literally everything that is not math uses. Unfortunately, although inductive logic (I think it's also sometimes called practical reasoning?) is much more useful than deductive logic, it is also much more difficult to do, and not nearly as well understood.
That's a good question - this is termed the "cooling flow problem". We expect to see lots of gas cooling in relaxed clusters (not the colliding one discussed here) as the gas is dense in the central regions. However there's a lack of evidence of cool gas, so most people think something is heating it (although there are many solutions possible http://uk.arxiv.org/abs/astro-ph/0010509). The ideal candidate is the central supermassive black hole (AGN), however it is difficult to understand how this process works. One idea is that sound waves can transport the energy from the black hole into the cluster, heating it (see e.g. http://chandra.harvard.edu/press/05_releases/press _120105.html)
Now it exists. Can I get free Mountain Dew to exist? Ok, I'm laboring the point. The truth is it *always* existed, whether we knew it or not. I think it's more to the point of "Dark Matter Proven", dontchathink?
:) Yeah, semantics, I know, but science and religion aren't opposites...though scientists and preachers sometimes are...
BTW: The Roman Catholic church in a similar way has decided that limbo/purgatory no longer exist; science and religion have a LOT in common.
--- For a good time mail uce@ftc.gov
I can see some new science fiction themes coming from this.
It's obvious now that I see the pictures that dark matter really is dark in that it's not signifigantly interacting with matter in the classical three dimentions of space except for gravity which is diluted through all the dimentions. You can somewhat see the gravitational lens slightly distorted and bleeding off slightly in the direction of the relatively insignifigant matter.
There must be at least one more dimention with matter in each three dimentional cross section not interacting with others. Is the matter similar or exotic in these hyper and subspaces? Gravity would be the same but would the other laws of physics apply equally?
But if there are parallel panes unless the matter is very unusual I would think that it would clump together just like stars and planets. But with gavity bleeding through wouldn't massive sun like objects contribute gravitationally to each other and hence in our space a sun would appear to have more mass than the gravity it generates...
The fact that your mind thinks MONDian theories are more reasonable is irrelevant. MOND theory says while the force of gravity is different at galactic distances, it is still centered at baryonic matter. This observation shows the center of gravity NOT at baryonic matter.
It takes many many instances of evidence to give weight to a theory. It only takes 1 failure to disprove it. This is it for MONDian as we know it.
The premise for this study is faulty, so it cannot be conclusive at all.
Just because MOND does not work on clusters doesn't mean that there is nothing wrong with our understanding of gravity. The utility of MOND is not that it is a good theory (actually it cannot be called a theory, there have been attempts to create a theory out of it, but I believe they have not yet succeeded). But its utility is that it works on a huge range of galaxies. This shows that for dark matter assumptions (dark matter is also not a theory, it is just an assumption) to be correct the dark matter must somehow be related to the normal matter. This is where the dark matter theories (the theories which define how the dark matter must be distributed within a galaxy) get into trouble. Because they cannot explain why the dark matter should be arranged only in that precise distribution. Why shouldn't they be more random, like the normal matter, and why should they assume the distribution to fulfill the MOND equation, which actually uses only normal matter.
That MOND doesn't work on clusters has been known for a long time. But then it doesn't need to work there to show the holes in our understanding. If it simply shows that our theories don't work at the Galactic level, then it is obviously true that it doesn't work on cluster levels too. Doesn't matter if MOND doesn't work there.
I don't know how long it will take for somebody to find the problem in the current theories, but the clue should come from studying the pioneer anamoly. I don't know why there are not more efforts to study the anamoly by simulating the same conditions again.
Presumably all this Dark Energy and Dark Matter originated from somewhere - I propose we call this origin 'The Dark Side'.
The same way, saying that something "exists" does not imply that it suddely came into existence.
...I'll believe it when I see it.
http://en.wikipedia.org/wiki/Tensor-vector-scalar_ gravity
"Tensor-Vector-Scalar gravity (TeVeS) is a proposed relativistic theory of Modified Newtonian dynamics (MOND), which purports to explain galactic rotation curves without invoking dark matter".
"it can explain the phenomenon of gravitational lensing, a cosmic optical illusion in which matter bends light"
I'd say the jury is still out regarding dark matter/energy..
Privacy begins with
From the article:
It turns out that the large majority (about 90%) of ordinary matter in a cluster is not in the galaxies themselves, but in hot X-ray emitting intergalactic gas.
Question:
How do we know that? This is the basic argument on which the separation of Dark/ordinary matter is done using the images
>>observed phenomena consistent with a theory that
>>claims dark matter's existence
>Or "evidence," for short.
Or, OJ Simpson Defense Team methodology, for short.
They came up with a theory to explain observed evidence. They were willing to tweak and modify it as needed to explain new observed evidence.
"never existed in the Creator"
That would make the creator limited, defined. Where did you get this idea about your shimmy creator? It's not a very good religion, compared with the breathtaking fantasies offered by competing religions. It's more like an "alien from another dimension created us as their pets" theory. I prefer the Great Green Arkleseizure.
--
make install -not war
The matrix uses FP math.
Wow, I should not post when knackered.
"Scientists have conclusive proof that dark matter exists. This does not rule out the possibility that dark matter doesn't exist, but is fascinating nonetheless!"
Yea! What has been proven is that the conjuncture (not even to the theory stage yet) about the notion that something affecting the gravitational forces in a way that is not consistent with current theory has yet again been shown to still be a problem.
The paper "The distribution of nearby stars in phase space mapped by Hipparcos. Astronomy and Astrophysics 329:920-936" by Crézé, M., Chereul, E., Bienaymé, O., and Pichon, C. performed what appears to be a much more detailed observational study right within the Milkyway Galaxy and discovered there is no dark matter. Now what?
Get real. Get facts!
Only Facts!
Theologians and scientists have much in common... They spend a great deal of time and energy trying to explain the unseen.
They argue amongst their ranks about who is dogmatic and who is objective. They also argue about that which is seen and what it means. Eventually interpretation becomes more essential than observation.
We're just like so many grasshoppers which can perceive the moon but don't know exactly what it is or what it really "means."
Wisdom begins with the realization of how puny one is in the universe. "A man's got to know his limitations"
Clint
quite simply, stuff isn't nothing.
The revolution will not be televised... but it will have a page on Wikipedia
There is a subtle issue with this paper which I notice the authors walked right around, whistling. That is, how do we know the majority of the mass of the clusters really *wasn't* in the gas clouds and condensed out during the collision?
As an example, this abstract talks about star formation initiated by ionization and shock fronts. The bullet part of the Bullet Cluster is a shock front thousands of parsecs long. As this shock travelled through the clouds, maybe the gas condensed into stars or proto-stars. These stars might not be completely formed yet nor strongly clustered and might be invisible to us. Maybe that matter remained with the clusters and didn't get swept along with the clouds.
The only thing the paper has to say about this is "...in the course of a cluster collision, galaxies spatially decouple from the plasma." I expect this will have to be looked at further.
In other words, maybe the observed clusters aren't represenative of typical intergalactic space. The hubristic use of the word "PROOF" in the title and closing sentence is unfortunate.
Equine Mammals Are Considerably Smaller
Next, do astrophysicists consider the effects of thermodynamics? You know, expansion, cooling, heating, enthalpy, etc... They seem to be assuming radiation~=temperature, so cold matter would be "dark". Do these guys really understand where the hot regions would be in such a collision?
"(...) we've come closer than ever to seeing this invisible matter," Clowe said.
If he's hoping to see the invisible, then I think someone's been throwing around the definitions here. If this is the same NASA that mixed metres and feet, maybe they should sort out their dictionaries.
But relatively speaking, there is no NASA at rest, of course. We're all spinning plutons and OMG It's full of stars!
Defining Statistics and Social Research
Would the existence of dark matter prove the aether to be true?
*Repent!Quit Your Job!Slack Off!The World Ends Tomorrow and You May Die!
So how did all the matter, compressed into the size of an electron before the Big Bang, get created.
In further news, the server hosting the "Dark Matter Exists" article was "slashdotted". Experts suggest that this proves the existance of a much more volatile substance, "Dork Matter".
. . . conclusive proof of dark matter.
You did not mean to say that. The scientific method does not admit of *conclusive* (final) proof of anything. One of the things that fuels the pseudo-science industries is this occasional sloppiness on the part of scientists and science journalists. They may be definitive, exhaustive or comprehensive, but scientific judgements are never privileged by finality beyond the pale of pure abstractions like mathematics.
illegitimii non ingravare
But there you're assuming there's some beginning point from which all time is measured. As if you were saying, "Since the beginning there must have been an infinite amount of time that's passed." But there was no fixed time of beginning, so saying there's an infinite amount of time that's passed before us is just as plausible as saying there's an infinite amount of time to come after us.
To put it another way: call the current time "0". How many real numbers are less than zero? (For that matter, how many real numbers are there between -1 and zero?) Does the fact that you can't traverse them all from the lowest to highest somehow mean that zero doesn't exist?
It's not the present that can't be reached from the beginning in this theory, it's the (non-existent) beginning that can't be reached from the present. Normal numeric operations and "intuitive logic" don't work with infinity. Not quite in the way you might expect, at least.
---GEC
I'm but the humble pupil, seeking to snatch the scratchbuilt pebble from the master's fully articulated hand
1. The proof itself is hinged on gravitational lensing. Isn't there a possibility that some modified gravity theory (not MOND, something else), that along with the modification of gravity, it might modify the concept of gravitational lensing too?
2. It is known now that gravity is indeed associated with matter. Supposing later on some theory proposes that the function of gravity, or maybe gravitons, has some vector properties which makes it move away from the matter in some specific circumstances.
I know that occams razor doesnt point to any of these ideas being true. But I was just hypothesizing that many theories can occur later which could explain this even using modified gravity theories.
rajmohan_h@yahoo.com
I don't know if you will ever see this, but I just wanted to say your post was the most succinct definition of "proof" and mathematics that I have ever seen.
Steve
A work that expires before its copyright never enters the public domain and thus enjoys eternal copyright protection.
THE END OF STRING THEORY: Calling the String Theorists' Bluff: All Tied Up & Strung Along--Hollywood String Theory Movie Tied Up & Strung Out: Hollywood String Theory Movie!!! Looking For Extras!!!
FOR IMMEDIATE RELEASE: ALL TIED UP & STRUNG ALONG, a movie about String Theorists and their expansive theories which extend human ignorance, pomposity, and frailty into higher dimensions, is set to start filming this fall. Jessica Alba, John Cleese, Eugene Levie, Jackie Chan, and David Duchovney of X-files fame have all signed on to the $700 million Hollywood project, which is still cheaper than String Theory itself, and will likely displace less physicists from the academy. "As contemporary physics is about money, hype, mythology, and chicks," Ed Witten explained from his offices at the Princeton Institute for Advanced Study, "The next logical step was Hollywood, although I thought Burt Reynolds should play me instead of Eugene Levy." Brian Greene, the famous String Theorist who will be played by David "the truth is out there" Duchovney, explained the plot: "String theory's muddled, contorted theories that lack postulates, laws, and experimentally-verified equations have Einstein spinning so fast in his grave that it creates a black hole. In order to save the world, we String Theorists have to stop reformulating String Theory faster than the speed of light. We are called upon to stop violating the conservation of energy by mining higher dimensions to publish more BS than can accounted for with the Big Bang alone, and I win the Nobel prize for showing that M-Theory is in fact the dark matter it has been searching for." Greene continues: "At first my character is reluctant to stop theorizing and start postulating, but when my love interest Jessica Alba is sucked into the black hole, I search my soul and find Paul Davies there, played by John Cleese. I ask him what he's doing in my soul, and he explains that the answer is contained in the mind of God, which only he is privy too, but for a small fee, some tax and tuition dollars, a couple grants here and there, and an all-expense-paid book tour with stops in Zurich and Honolulu, he can let me in on it. And he shows me God in all her greater glory, as he points out that we can make more money in Hollywood than writing coffee-table books that recycle Einstein, Bohr, Dirac, Feynman, and Wheeler. I am quickly converted, and I agree to turn my back on String Theory's hoax and save Jessica Alba." But it's not that easy, as standing in Greene's way is Michio "king of pop-theory-hipster-irony-the-theory-of-everything- or-anything-made- you-read-this" Kaku, played by Jackie Chan. Kaku beats the crap out of Greene for alomst blowing the "ironic" pretense his salary, benefits, and all-expense paid trips depend on. "WE MUST HOLD BACK THE YOUNG SCIENTISTS WITH OUR NON-THEORIES!! WE MUST FILL THE ACADEMY WITH THE POMO DARK MATTER THAT IS STRING THEORY TO KEEP OUR UNIVERSE FROM FLYING APART, OUR PYRAMID SCHEMES FROM TOPPLING, AND OUR PERPETUAL-MOTION NSF MONEY MACHINE FROM STOPPING!!" Kaku argues as he delivers a flying back-kick, "There can be ony ONE! I WILL be String Theory's GODFATHER as referenced on my web page!! I have better hair!" But Greene fights back as he signs his seventeenth book deal to make the hand-waving incoherence of String Theory accessible to the South Park generation, senior citizens, and starving chirldren around the world. "Kaku! Kaku! (pronounced Ka-Kaw! Ka-Kaw! like Owen Wilson did in Bottle Rocket)," Greene shouts. "It is theoretically impossible to build a coffee tables strong enough to support any more coffee-table physics books!!!" "Time travel is also theoretically impossible, but there's a helluva lot more money for us in flushing physics down a wormhole. Nobody knows what the #&#%&$ M stands for in M theory ya hand-waving, TV-hogging crank!!! Get it?? Ha Ha Ha! We're laughing at the public! We're the insider pomo
Actually the evidence is rather on the side that if you can reliably feed everyone in a country, then natality drops like a brick there.
People in underdeveloped countries that tend to have lots of children need them in later life to take care of their aged parent who would otherwise starve.
People in more developed countries have way fewer children because they by and large want to do something else with their life than care for lots of brats. I'm saying this as a parent.
* ducks *
I always wondered if this has any relation to theology where it is thought in certain religons that there are 2 sides, good and evil, which is typically represented as light and dark.
Similarly there are a lot of examples of this in science specifically in physics where there are 2 distinct opposing sides of a given theory. (atoms, magnetisim, matter, etc)
I wonder if (assuming theologians are right about the existence of good vs evil) this has any correlation to spirits that might exist where dark matter might represent evil energy and good represents good energy.
I often think about this when looking in the night sky and wondering to myself if the stars and the dark areas surrounding them are somekind of physical representation of the forces of good and evil, as (for one example) the christian bible does reference a relation to the stars in the sky to evil and good spirits/forces.
I myself do believe that spirits exist but that we currently are unable to use science to detect them, not that it is impossible to do so but it would be the same thing as a world full of dogs wondering about the existence of a widely held belief about "colors".
the difference between anti matter and dark matter? Are they one in the same or do they differ in someway?
The only person who seems to be arguing for perfection here is you.
I certainly haven't seen anyone who's sane and educated insist that we have perfect knowledge of anything. Have you considered that perhaps you're just an idiot who can't make a coherent argument, so builds up a strawman to knock down instead?
The only people who claim "science" is god/perfect/infallible are zealous idiots who are trying to make the claim that *others* worship it. Just like you!
Since I can't tell them apart, I treat all ACs as the same person.
so the normal matter is actually hanging out with the dark matter rather than the other way around
I don't see how they could tell that. They "go together" it appears. Plus, if the dark matter *always* seems to hang out with regular matter, then that could mean that the gravity of regular matter does not behave in a Newtonian way. In other words, they have not sifted out dark matter from everything yet to see it in isolation. They have only isolated regular matter from plasma in a certain way, not dark matter from anything. The accounting here I find confusing.
Table-ized A.I.
You're assuming free choice. In most 3th world countries, they don't have reliable contraceptives due to their high prices (relative to the income of the local people).
You're correct that western culture tends to have small families, but this is only because we can afford "protection". Without our anticonceptives we too would have families of around 10 children no matter how much the wife would like to focus on her cariere.
And trust me on this: women have the need for sex just like men. They are just better at hiding it and more picky. Celebacy is not much of an option in this.
From TFA: ... constitutes only about 5% of the energy of the universe, with 25% being dark matter and 70% being dark energy. The challenge for early-twenty-first-century cosmology will actually be to understand the nature of these mysterious dark components
ordinary matter
Also in the news:
We're now certain that epicycles are the correct model of the planets. The challenge for early (negative) 2nd century cosmology will actually be to understand the nature of these mysterious circles within circles.
Correct me if I'm wrong, but I thought that baryonic particles only included those made of quarks - your protons, neutrons, etc. To be even more specific, my recollection was that to be a baryon ("heavy particle"), a particle had to have three quarks. The two quark models (your pions, kaons, etc.) are called mesons ("mid-weight particles"). And your neutrinos, electrons, etc, were yet a third type - the leptons ("light particles") - that weren't made of quarks at all.
In practice, I doubt this distinction matters very much, because the leptons don't weigh much of anything, and the mesons are too unstable to be a very big contituent of the universe.
Sean
Oh yeah? How else then do you explain God telling Abraham to sacrifice Isaac and then Abraham making a good go at it before an Angel steps in to stop him?
The toothfairy gives me a whole dollar!
--
make install -not war
I'm assuming basic free choice, yes, but not in the direction you assume.
In many countries with population problems, even very poor ones like African nations and India, contraceptives are available freely : condoms, the Pill, IUD and even chirurgy where available, up to free abortions. Education about family planning is also widespread. These are very cheap options compared to increased population burden. Family planning are very big items in the government of such nations.
In many nations, people exercise free choice in the direction of large families despite strong government incentives to have fewer children. The situation is particularly intense in China in that regard.
There are still some countries where governments disapprove of contraception, but these are in the minority.