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The Hardware That Searches For Dark Matter (hackaday.com)
szczys writes: Deep in a gold mine in South Dakota, the Large Underground Xenon experiment waits in the darkness for a tiny flash of light that signals that dark matter actually exists. So far we theorize that it does exist, and have gone to great lengths to build hardware to detect dark matter. Very cold, very pure liquid xenon sits waiting for a dark matter particle to strike the nucleus of a xenon molecule, producing a distinct pattern of photons through scintillation. An array of photomultiplier tubes detect the photons, whose pattern is processed by FPGAs on custom boards connected using HDMI. The experiment has generated a list of properties not possessed by dark matter; running for several years no evidence of the particles interacting with the xenon have been found. But when the data collection concludes this year, a much larger version of the impressive hardware will be built.
Why not just walk around barefooted in the dark until you stub your toe on it? That's how I usually find things I otherwise cannot detect any other way.
Hmmm .... so I'm going to have to stretch my little monkey brain and hopefully someone more knowledgeable can chime in ...
I see reference to WIMPs in the article, so in some ways do we consider Dark Matter to be kind of like a neutrino? All around us but not generally interacting with us?
So instead of there being vast tracts of stuff we simply can't figure out where it is, it's spread throughout?
The overall underground detection mechanism sounds like the Sudbury Neutrino Observatory, or that Ice Cube deal in the Antarctic (Russia?)
I've always thought it wasn't assumed to be floating around us but not interacting, but I ain't no particle physicist.
Is Dark Matter more like neutrinos than not? Or entirely different, but with enough commonality to confuse a layman?
Lost at C:>. Found at C.
How does that work?
Why are they using HDMI cables to transmit the information?
Dark matter! Yeah, that's the ticket.
Probably looking for illegal grease.
Have gnu, will travel.
It's a lot more likely that dark matter and dark energy are just math errors that don't take into account proper universe/space expansion and doesn't understand how gravity really works.
Care to show your math on that? We can then compare it to all the scientists who already did the math a few million times showing the same results you say are wrong.
There is even a Nobel prize or three in it for you.
It's settled science ... just like large squids do NOT live in the ocean, the four humors control your illnesses (so do the bumps on your head btw), Darwin's pangenesis, the earth being hollow, and the steady state of the universe.
... let alone choices!!
Which physicists think dark matter is real? They all do.
It's settled science !!
See scientists are smart and we are all grovelling fools in their presence. We can't possibly make our own opinions
Go check out this website about the brilliant things scientists have uncovered:
https://en.wikipedia.org/wiki/...
Dark matter and dark energy have multiple independent lines of supporting empirical evidence. I presume you are willfully ignorant of this. Perhaps you can manage to keep it to yourself next time.
Those who advocate genocide deserve every protection afforded by law, and none afforded by common human decency.
processed by FPGAs on custom boards connected using HDMI.
Just because you use hdmi cables doesn't make it hdmi.
If you are emphasizing the "multitude" of sources, then you are falling victim to the idols of the tribe as Bacon described it.
Bacon, you know, who is sometimes referred to as the father of science (but in truth abandoned by modern scientists).
Converging validity is the false hope people leaned on in The Emporer's Clothes. Broad is the path that leads to destruction and many follow it!
Better to be happy and counted among fools I say.
Why would we expect to see it if we merely multiply the size of the experiment?
Because the event rate scales with the mass of the detector: if you have to wait one hundred years for one event with a 1kg detector, you only have to wait 1 year with a 100kg detector, and a month with a 1000kg detector.
Maybe have an engineer included in the hunt!
Wow! I bet they never thought of having engineers help build the detector! Those silly scientists.
I'm guessing that the "issue" is that our theories about what dark matter actually IS are wrong enough that we don't understand how to detect it.... Or, there is some observation lens that makes "dark matter" appear to be necessary to account for things, but it's really just appears that way do to local conditions or doesn't exist here, deep in a gravity well next to a star. Ah, some physicist's PHD thesis awaits...
But what do I know.. I'm just a computer programmer who's late to get lunch and has had too much caffeine today who didn't stay at a Holiday Inn express last night..
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Could well be true, but then our theory of gravity is wrong because stars in galaxy rotate at wrong speed at given distance from center.
If we don't find anything, how long do we keep looking?
There's a point at which the detectors will get sensitive enough that they start seeing neutrinos, and then the neutrino signal will swamp any Dark Matter signal. This is a couple of generations away in terms of technology development.
Lack of results doesn't always mean lack of progress, the lack of results can sometimes be interesting and still help us learn new things. if we already knew how to detect, and all the properties of WIMPS then why bother building the experiment to begin with? we would have nothing new to learn.
Finding out what properties WIMPS dont have helps refine our current theories. Some of those theories may have predicted we would see some of those properties, but because experimentation rules it out we now know those are dead ends and so can focus our time on other theories. Lack of results allows us to adjust and focus our experiment in ways that are more likely to receive positive results.
Hi, this is the internet. People come here specifically to run their mouths off on subjects that they really shouldn't bother having a thought on. I am frequently guilty of this.
If we don't find anything, how long do we keep looking? Given that it is inherently difficult to prove the existence of something that is by definition elusive, what are the chances it isn't there in the first place? Furthermore, how much looking with no results will get us a reasonable certainty of that?
Yes, dark matter is elusive. But so are neutrinos, and we managed to find ways to observe them. Dark matter is postulated to interact via the weak force, just like neutrinos, so their detection strategies are similar.
The longer we look without seeing anything, the lower the estimate will be for the density of dark matter. At some point that density may fall well below what is expected from other experiments and theories. At that point one starts to doubt the theories, and to look for ways to revise them. But you need to look long enough to be sure the theories are wrong. Also, it could be that dark matter exists, but has a much lower density than theory predicts. To confirm that, you need to keep looking. Obviously not forever, but as long as you can.
Some of the most important experiments in history have failed to measure what theories predict, and thus have driven significant improvements in theory. Consider the Michelson-Morley experiment, which failed to measure the aether, but led to Einstien's theory of relativity. Or the Solar neutrino problem, which occurred when neutrino observatories measured about a third of the solar neutrinos that were expected from theory, and which was resolved when it was discovered that neutrinos, which come in three different types, can actually change their type on their way from the Sun to the Earth.
If it weren't for deadlines, nothing would be late.
I googled various interaction probabilities, which are expressed in units called barns:
http://www.physics.purdue.edu/...
neutron hitting uranium nucleus: 1 barn
helium nucleus hitting gold nucleus: 100 barns (Rutherford experiment 1911)
anti-neutrino captured by proton making a neutron: 10E-17 barns (first detected 1956)
WIMP hitting a xenon nucleus: 10E-21 barns? (year???) need to 10,000 times better than neutrino detector
Numbers are actually ranges including factors like particle energy and angle.
The longer we look without seeing anything, the lower the estimate will be for the density of dark matter. At some point that density may fall well below what is expected from other experiments and theories. At that point one starts to doubt the theories, and to look for ways to revise them. But you need to look long enough to be sure the theories are wrong. Also, it could be that dark matter exists, but has a much lower density than theory predicts. To confirm that, you need to keep looking. Obviously not forever, but as long as you can.
You don't identify what type of "density" you are referring to - mass density or particle density. For mass density we have a very good idea of what it is from direct measurement of its gravitation - that is not really a matter of theory. Now particle density depends on what the mass of what the particles are. There we have room for lots of uncertainty, and of course there is the even bigger uncertainty about how the interact with known types of matter - regardless of particle density.
Second class citizen of the New Gilded Age
You don't identify what type of "density" you are referring to - mass density or particle density. For mass density we have a very good idea of what it is from direct measurement of its gravitation - that is not really a matter of theory. Now particle density depends on what the mass of what the particles are. There we have room for lots of uncertainty, and of course there is the even bigger uncertainty about how the interact with known types of matter - regardless of particle density.
Excellent points. Thanks for the improvement.
If it weren't for deadlines, nothing would be late.
Your comment does little to tell me about the advantages of modern science ... but you punctuate it with a perjorative expression.
Unclear is if you intended to be persuasive.
Scintillation in liquid Xenon happens when Xe atoms are ionized and temporarily form molecules before returning to a neutral state and emitting photons.
Then TF summary is wrong when it says "liquid Xenon sits waiting for a dark matter particle to strike the nucleus of a Xenon molecule".
It's also entirely likely that the person who wrote the summary wrote "molecule" when they meant "atom"...
This. TFA doesn't contain the word "molecule," only TF summary does. Would make no sense for this detector to contain macroscopic quantities of exotic polyatomic Xenon molecules.
That that is is that that that that is not is not.
Amazing i agree with u i am happy your post... http://www.tanya-roy.com/
molecular xenon exists, used in some lasers
more likely anonymous cowards on slashdot are ignorant and uneducated in physics
It's been a while since I've read Bacon, but apparently it's the same for you (or you've abandoned him too). The idols of the tribe are basically groupthink, and it's certainly something to avoid. What AC is talking about is multiple independent lines of evidence, which is completely different. If everybody claims something and says it's common sense, it's often very worthwhile to quantify it or formalize it or try to find where it breaks, and that's countering the idols of the tribe. If a line of investigation seems to imply something, and more and more do, then we have stronger evidence, which is something entirely different.
Not to mention, what's this nonsense about being true to Bacon? He wrote a long time ago, and we've come up with better ways to study things since. Science does not have sacred texts. Almost everything is subject to change.
BTW, the link says that some people figured that their changed gravitational theory accounts for galactic rotation curves and the Bullet Cluster, which isn't all the evidence for dark matter. It's an interesting finding, but hardly definitive, as the article points out.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
You got me that multiple independent lines of evidence is different from different sources.
Most science today is researchers getting paid to prop up certain political opinions. This is a case where ideology isn't really related to the outcome, but reference to the prevalance of the view is taken as evidence of its truth.
What would Bacon say about researchers trying to find a way to "hide the decline" and failing to find ways to reject others peer reviewed studies because it doesn't align with their buddies?
If you don't think big science has its sacred cows, I disagree.
Personally I'm waiting for them to find that they don't have any of the properties that they theorize so that we can watch them flounder for a new theory to support their horribly broken model. It has been quite entertaining for some time watching them make shit up and pretend it is scientifically valid.