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Missing Matter... Still Missing
squidfrog writes "Nature.com, PhysicsWeb, and the BBC all report on the latest results from the Cryogenic Dark Matter Search. 'The most powerful search yet for the Universe's missing matter has come up empty handed, contradicting an earlier study that claimed to have seen new particles.' 'A favoured theory is that the dark matter consists of Wimps (weakly interacting massive particles) about a thousand times more massive than a proton, one of the particles found in an atom's nucleus... on the rare occasions a Wimp strikes an ordinary atom, the effect should be noticeable.' 'Writing in the Physical Review Letters, the team says that while a detection has yet to occur, there is now a better idea of how much dark matter must exist.' They 'hope to improve the sensitivity of the experiment by another factor of 20 over the next few years.' What's 20 times 0? And don't tell me zero!"
However since it started running in November last year, the detector has not seen a single WIMP.
Then they decide to make a more sensitive detector so that they can "not" detect at an even higher level?
Physicists with the CDMSII experiment say they will now add another 24 crystals to the detector, increasing its sensitivity tenfold.
Okay, maybe I am being a bit silly, but, I still don't see how they can know the detector is working. I don't even know how the WIMP can make the thing "ring" once it, itself, is subject to the 1/10 degree above absolute Zero conditions. And then, somehow, with no data, they can extrapolate more accurately how much dark matter is in the universe. Well, they would say the lack of WIMPS is data but I'm not buying it. Enough /. folks have worked in research to know better than to buy into those kinds of statistical games (you can prove almost anything with non-parametric statistics).
Happy Trails!
Erick
http://www.busyweather.com/
I thought the usual rule in science was, if your theory conflicts with your observations, there is something wrong with your theory. Maybe there is no "missing matter", just an incomplete or defective theory of gravity.
Mea navis aericumbens anguillis abundat
because there isn't any.
The astronomers have been seeing something they do not understand, and so they assume it is dark matter. The same result could be gotten by a decaying speed of light.
Unfortunately, that requires another rewrite of physics, from the ground up. However, looking for something understood gets more grant money.
... would be the efficiency of the experiment (assuming it would fail the same way as this one), not the sensitivity of the equipment used.
That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?
Yah, you're missing the scientific paper. This is a one page write-up written by a journalist. The one page write up doesn't describe how they know the detector works, but I'm sure they have _some_ means of testing that it does. Blame the article, but at this point you can't really accuse anyone of doing shoddy science for grant money.
AccountKiller
I am not a physics/math expert, but assuming that dark matter does exist, it only proves that the equipment currently used has a sensitivity that is approaching zero, but not zero. But anyone who has seen a graph of an asymptope, it is not very promising especially if you push x approaching infinity. Even if you were to multiply x by 20, while you are out to infinity, by not knowning where exactly they are relative to the origin on the graph, a factor of 20 may not be all that significant... :-/
But at least they are still trying... and trying... and trying some more.
Wow, what a suprise, hyperbole in the Slashdot summary.
The fact that the detector hasn't found the thing it was designed to detect doesn't mean that it has a zero sensitivity or that the hypothesis is bogus(you can't readily prove a negative except by proving a contradictory positive), just that, in the finite time it's been running, it hasn't been sensitive ENOUGH to detect anything. 20 x 0.00000000000000000(you get the picture)001 is still an improvement, and may be enough to make progress.
NB: YMMV. IANAL. Take the above with a grain of salt.
GR is perhaps the most well-tested physical theory yet developed and, as such, you can't say that it's "wrong". It plainly isn't once you remain within its field of reference.
You miss the point.. I'm citing the effects as evidence the theory is incorrect.
Simon.
while I agree that the case for GR is pretty compelling, this same line of thought is why it took so long for ptolemy's ridiculous (in hindsight) orbits to be debunked. "but they solve so many problems that cannot be solved otherwise that it's preposterous to consider anything else"... ditto for many other "givens" (sun circles the earth, etc) in history. my point is that a scientific mind is always prepared to be repeatedly shown completely wrong - and in fact delights in this process, as it moves understanding closer to fullness.
La via sola al paradiso incommincia nel inferno
That sounds like another phenomena of a less scientific nature... ghosts! In some belief systems spirits or souls are more massive or dense then normal matter as well.
I guess. The difference is that scientists are examining something in the universe, and testing possible explanations for a fit. Any number of them, or even a regular Joe with access to the equipment and data can see it for himself.
None have yet produced any repeatable, measurable observations of ghosts.
Maybe there is no dark matter. Science only describe predicted observations. Reality doesn't necessarily obey the laws of science. Belief in such is similar to belief in a deity. Maybe the universe is governed by the laws of science, but then again, maybe it is governed by such-n-such a deity.
So if a theory isn't cutting it, then create a new model of whatever observation that you are trying to describe. It seems silly to try to fit nature to the theory, and not the theory to nature.
The theory of dark matter is based on the assumption that the basic properties of the Universe have never changed over time. If the intrinsic properties of space itself HAVE changed significantly, then there is no need to postulate such a thing as dark matter. Scientists are very reluctant to accept new data that shakes their preconceived pet ideas to their foundations. It took over 200 years after Roemer first measured a finite light speed, for the majority of scientists to accept the fact that light did not get instantaneously from point A to point B, as was the belief for centuries. In the same way, the majority of scientists today refuse to even consider the idea that some very fundamental "constants" may have changed dramatically since the beginning of time. For example, the cause for the "Red Shift" of distant star light is traditionally attributed to the Doppler effect, and in light of that INTERPRETATION of the cause for an observed fact, (the shifted light) all sorts of cosmological observations are very difficult to explain. Humans (including scientists) like to assume that certain things stay the same for all time, but that is a fervently desired wish based on faith, not observed fact. It seems that in the physical universe, there is nothing as constant as change! AAW
All theory is gray
The thing that makes the dark matter explanation compelling is that it makes so many different observations work. We don't have to fine tune things so much - it all fits together. Here are some examples.
1. Galaxy rotation curves - you can watch the orbits of stars in a galaxy to determine the distribution of matter in the galaxy. This shows that there is a lot more matter than can be accounted for by the stars and that it is distributed differently.
2. Gravitational lensing - you can see how light is bent by distant galaxies to map out their matter distributions. Again, there's a lot more matter than the stars can account for, distributed differently.
3. The cosmic microwave background - this one is complicated, but the idea is that you look at the "afterglow" of the big bang, released when the universe was as dense and hot as the surface of a star. We understand the physics of matter at these temperatures very well, and by studying the signatures of vibrations in this hot plasma, we can measure the properties of the early universe. We can see from this that the universe contains a lot of matter, and that the large majority of this matter is not composed of ordinary atoms (hard to explain, but fairly rock solid).
4. Light elements - Most of the universe's helium, deuterium, lithium and beryllium were created in the early universe, not in stars (the conditions aren't right). Again, the physics is very well-understood, nothing fancy. By studying the relative ratios of these elements, we can figure out the properties of the plasma in which they were formed (a bit hotter and you get less deuterium, the temperature falls too quick and you get less helium, stuff like that). Again, the universe has a lot of matter, and most of it isn't made of atoms.
5. Structure formation - if you work things out on supercomputers, you find that (if the universe containst only ordinary matter) the universe hasn't been around long enough to form the galaxies and galaxy superclusters that we see. Adding dark matter to the mix makes galaxies form faster - just enough faster!
And the beautiful thing is that all of these different arguments give essentially the same answer for the amount of dark matter and its basic behavior. You can tweak your theories to explain some of these observations, but no one has been able to explain them all - except with dark matter, the SIMPLEST explanation!!
Before you say something is "clearly inferior intellectual flotsam", learn what you're talking about...
As for the description of gravity being incorrect, I hate to tell you this, but general relativity solves *so* many problems that cannot be solved otherwise that it's preposterous at this point to consider anything else.
Newton's physics accurately describe a lot of things - and are still very useful - but they are *not* a correct description of the way the universe really works.
General Relativity is the same way. It accurately describes many things, but eventually it will be superceded by a more complete theory.
"...always new atoms but always doing the same dance, remembering what the dance was yesterday." -Richard Feynman
Others have given you examples of why GR may be incorrect as it relates to gravity
But that doesn't mean their interpretation of the data is correct. If the accumulated evidence against GR as it relates to gravity was so clear this would be a discussion between scientists and the GR equivalent of the flat earth fringe who keep pushing the old GR/gravity line. But it hasn't come to that yet so discussion is still valid.
Is this the first time ever that data has suggested that GR may be incorrect as it relates to gravity. If not, what was the outcome.
prove your point with evidence
I thought the scientific method was to disprove your point with evidence. If you fail to do that you strengthen your view that the point you have is less likely to be incorrect than any alternative. As far as I can tell he merely suggests that the state of current observations are insufficient to show GR AIRT gravity to be unsustainable.
.I'm not a scientist either but this isn't a scientific forum. So it's onl a laymans view of how it works.
i'm an idiot i confused now with not... stay off the drugs man
The best education consists in immunizing people against systematic attempts at education. - Paul Feyerabend