Cosmology Shrieks in the Dark
Secular cosmologists keep spending more and more money looking for dark matter. So far it’s all trick and no treat.
The quest for dark matter is approaching half a century with no luck. Repeated promises that astronomers “are getting warmer” keep failing. Still, nations are spending prodigious amounts of money to build bigger and more sensitive detectors. If cosmologists don’t find the mysterious unknown stuff soon, the “hard science” of physics will suffer a devastating blow. Dark matter may go down in the history of science as the phlogiston of the 21st century.
Last chance for WIMPs: physicists launch all-out hunt for dark-matter candidate (Nature). The USA, Italy and China are competing to upgrade their giant underground detectors in a last-ditch effort to find “Weakly Interactive Massive Particles” (WIMPs), large subatomic particles that are favored dark matter candidates. Italy’s detector is named “DARWIN.” Filling these giant tanks with supercooled xenon is costing much of the global budget of the noble gas. Is it worth it for something that may not even exist?
Physicists might have no choice but to club together because of the sheer quantity of xenon needed. The noble gas is difficult to obtain in large quantities owing to the energy-intensive process needed to extract it from the air and because of competing demand from electronics, lighting and space industries. One kilogram can cost more than US$2,500. Darwin’s 50 tonnes would be close to the world’s annual production of around 70 tonnes, meaning that — even if all 3 existing detectors combine their 25 tonnes — a future experiment would need to buy the rest in batches over several years. “We have to plan very carefully for it already now,” says Baudis.
A new way to search for dark matter reveals hidden materials properties (Phys.org). Meanwhile, physicists at the Chalmers Institute of Technology are describing properties of something that may not exist. “The new calculations enable theorists to make detailed predictions about the nature and strength of interactions between dark matter and electrons, which were not previously possible.” Actually, it’s possible to predict the properties of anything that is all free parameters and no data.
We know very little about dark matter, other than that it exists.
The puzzle of the strange galaxy made of 99.99% dark matter is solved (Institute of Astrophysics, Canary Islands). How could a whole galaxy be made up of stuff that may not exist? It can’t. The scientists who announced the galaxy were mistaken. Another look showed that galaxy Dragonfly 44 has no more dark matter than other galaxies – that is, if they have any at all. Dark matter is not detected directly; it is inferred from the motions of matter.
New theory on the origin of Dark Matter (University of Melbourne). It just bubbled up, simple ones, during the Big Bang. That’s why it’s so hard to detect. Aren’t you glad that’s solved?
“These phase transitions are expected to have taken place in the early universe and can be similar to bubbles of gas forming in boiling water. We show that it is natural to expect dark matter particles to find it very difficult enter [sic] these bubbles, which gives a new explanation for the amount of dark matter observed in the universe.”
But it isn’t observed. It is inferred. It’s like the mysterious “inflaton” particle that was concocted to explain cosmic inflation, which Alan Guth concocted. When theory requires a particle, scientists will search forever to find it until a scientific revolution occurs that no longer needs the particle because it no longer trusts the theory.
Precision metrology closes in on dark matter (Phys.org). They don’t know what it is, but if they find it, they’ll be able to measure it to better precision than ever. Let’s hope their tools can find other uses in case dark matter never turns up.
The existence of dark matter is indirectly evident from gravitational effects at galactic and cosmological scales, but beyond that, little is known of its nature. One of the effects that falls out of theoretical analysis of dark matter coupling to particles in the standard model of physics is a resulting oscillation in fundamental constants. Ye and collaborators figured that if their world-class metrology equipment could not detect these oscillations, then this apparently null result would be useful confirmation that the strength of dark matter interactions with particles in the standard model of physics must be even lower than dictated by the constraints so far on record.
A Billion Tiny Pendulums Could Detect the Universe’s Missing Mass (National Institute of Standards, NIST). Forget the underground xenon; this group thinks “a billion millimeter-sized pendulums would act as dark matter sensors.” Who is going to build those? Maybe the companies that make smart phones could help.
To fabricate so many tiny sensors, the team suggests that researchers may want to borrow techniques that the smartphone and automotive industries already use to produce large numbers of mechanical detectors.
Thanks to the sensitivity of the individual detectors, researchers employing the technology needn’t confine themselves to the dark side.
But do companies working to make a profit want to blow that much money on a 50-year fruitless quest?
A Major Milestone for an Underground Dark Matter Search Experiment (Lawrence Berkeley National Laboratory). They reached a “major milestone” in building their expensive detector, but NOT a major milestone in finding the mysterious WIMPs. The last version of their xenon-filled underground LUX detector found nothing (22 Nov 2019, 21 July 2016). This quest for nothing is funded by the DOE (US Dept of Energy). Your tax dollars at work.
“We’ve certainly done this before, but never at this scale,” he said. LUX used about one-third of a metric ton of liquid xenon, while LZ will have 10 metric tons of liquid xenon and will be about 100 times more sensitive to dark matter particle interactions.
“We are going into the unknown now.”
Dark matter: our method for catching ghostly haloes could help unveil what it’s made of (The Conversation). Andrea Font traces the search for dark matter back 70 years.
The search for dark matter – an unknown and invisible substance thought to make up the vast majority of matter in the universe – is at a crossroads. Although it was proposed nearly 70 years ago and has been searched for intensely – with large particle colliders, detectors deep underground and even instruments in space – it is still nowhere to be found.
So how do you keep a 70-year search going? Promissory notes work. ‘Oh, but think how important phlogiston will be if we ever find it! It might even cure cancer and solve global warming!’
Dark matter remains a mystery, but there’s a huge amount of work going into solving it. Whether the answer will come from instruments on Earth or astrophysical probes, it will no doubt be one of the most important discoveries of the century.
Distant alien planets could be turned into dark matter detectors (Live Science). Astrophysicist Paul Sutter illustrates the overconfidence of cosmologists in their theory: “We know very little about dark matter, other than that it exists,” he states with Tontological bravado. Maybe scientists could turn exoplanets into dark matter detectors. Why not? Nothing else works. But will the mission planners of the James Webb Space Telescope, scheduled to launch (finally) late next year, be willing to give up precious time to observe thousands of exoplanet temperatures, as Sutter suggests? Don’t count on it. The mega-expensive infrared space telescope has a lifetime of 6-10 years, and after numerous delays and cost overruns, making astronomers wait for almost 20 years to get the thing off the ground, they are going to be very particular about observing priorities.
Particle Physicists Continue To Make Empty Promises (BackReaction blog). In text and video, cosmologist Sabine Hossenfelder complains that all this talk about dark matter is teasing the public with unfalsifiable bravado.
Let me unwrap this for you. The claim that dark matter is a guaranteed result, followed by weasel words about weakly interacting and thermal origin, is the physics equivalent of claiming “We will develop a new drug with the guaranteed result of curing cancer” followed by weasel words to explain, well, actually it will cure a type of cancer that exists only theoretically and has never been observed in reality. That’s how “guaranteed” this supposed dark matter result is. They guarantee to rule out some very specific hypotheses for dark matter that we have no reason to think are correct in the first place.
Lots of theories are “falsifiable” in principle, she explains. That doesn’t mean they are scientific. ” There are lots of falsifiable hypotheses that are clearly unscientific,” she says with examples, such as predictions of what will happen tomorrow when there is no reason to expect the event. So far, she goes on, cosmologists are trying to find dark matter by ruling out possibilities. Is that a scientific approach?
The same is the case with particle physicists’ hypotheses for dark matter that you are “guaranteed” to rule out with that expensive big collider. Particle physicists literally have thousands of theories for dark matter, some thousandths of which have already been ruled out. Can they guarantee that a next larger collider can rule out some more? Yes. What is the guaranteed knowledge we will gain from this? Well, the same as the gain that we have gotten so far from ruling out their dark matter hypotheses, which is that we still have no idea what dark matter is. We don’t even know it is a particle to begin with.
At some point, after so much trying and so much expense, astronomers may have to just decide it’s not worth it to pursue this dark vision any longer. The bright dawn of All Saints Day will overwhelm the haunting gloom of the witches’ Sabbath.
Perhaps the solution is to kick the moyboys out and take seriously the idea that we live in a young cosmos. That would not be a cheap trick. Saving so much money would be a treat.