December 30, 2020 | David F. Coppedge

2020 Ends with No Dark Matter

Cosmologists end another year without finding dark phlogiston. What will it take to cure them of their pet myth?

Like most gamblers, scientists will persist beyond past reasonable effort, because they know that some people do win. The neutrino was discovered after it was predicted from theory. Physicists discovered that neutrinos can change flavor after years of puzzling over the “missing solar neutrino problem.” There are other cases in the history of science where persistence paid off. But the wins of other gamblers do not imply that you will win. There are times when retreat is the better part of valor. That is especially the case when efforts become more and more ridiculous.

In search for dark matter, new fountain design could become wellspring of answers (Phys.org). Scientists from the USA, Canada and the Netherlands are searching for a theoretical particle called the Z’ Boson as the carrier for dark matter.

You can’t see it. You can’t feel it. But the substance scientists refer to as dark matter could account for five times as much “stuff” in the universe as the regular matter that forms everything from trees, trains and the air you breathe, to stars, planets and interstellar dust clouds.

Though scientists see the signature of dark matter indirectly in the way large objects orbit one another—particularly how stars swirl around the centers of spiral galaxies—no one knows yet what comprises this substance. One of the candidates is a Z’ boson, a fundamental particle that has been theorized to exist but never detected.

In the same way, though, 18th century chemists pursued phlogiston indirectly. The “signature” of the mythical substance was detected in the products of combustion, they thought, even though phlogiston had to have weird properties, like negative weight! When oxygen was discovered, phlogiston theory slowly evaporated away.

New Hubble Data Explains Missing Dark Matter (NASA-Goddard Space Flight Center). The headline is misleading. Dark matter is still unexplained. What they think they are explaining is why two galaxies that seemed to be devoid of dark matter look the way they do. The dark matter is there, they believe; it’s just being disrupted by tidal forces. See also Phys.org article “The case of the missing dark matter: new suspect found in galactic mystery” where Sherry Landow of the University of New South Wales says, “Dark matter—an invisible substance as enigmatic as its name suggests—is a key ingredient in helping galaxies form and stay alive.” Live Science also played along with this act, failing again to ask any hard questions.

Photograph of dark matter. White background provided for contrast.

Seeing dark matter in a new light (Phys.org). This headline is also misleading. Nobody is “seeing” dark phlogiston because it is invisible to every detector that has tried to find it. “So how do we measure what cannot be seen?” says Morgan Hollis of the Royal Astronomical Observatory. “The key is to measure the effect of gravity that the dark matter produces.” That is an indirect measurement that is highly theory-laden.

New constraints on alternative gravity theories that could inform dark matter research (Phys.org). In this post, Ingrid Fadelli peers into the crystal ball of theory, asking why dark phlogiston continues to evade detection.

While particle theories are currently the most favored explanations for dark mater [sic], physicists have still been unable to detect dark matter particles in ways that would confirm or contradict these theories. Some theorists have thus been exploring new theories of gravity that clearly account for and explain the existence of this elusive type of matter. In order to obviate the need for dark matter, however, these theories should be aligned with cosmological observations gathered so far.

The physicists from JPL and Princeton thought about this, but could not come up with alternate gravity theories that were credible.

“We showed that any theory that tries to explain dark matter by changing gravity (rather than by having a new particle) would need to have a very unique form,” Pardo explained. “In fact, this form would be so unique that it would probably lead to some pretty crazy motions of galaxies near us, which we see no evidence for. So the simplest explanation for dark matter is still that it is some particle.”

Ripples in space-time could provide clues to missing components of the universe (Phys.org). Another team from the University of Chicago, with collaborators, is looking for dark phlogiston in gravitational waves, using the LIGO interferometer.

Searching for invisible axion dark matter with a new multiple-cell cavity haloscope (Phys.org). Ingrid Fadelli writes about another candidate particle, the mythical axion. Korean research SungWung Youn gets a little silly trying to use their high-tech cavity detector: “I dubbed this cavity design ‘pizza cavity’ and compared the gap to a pizza saver, which keeps slices intact with its original toppings.”

Exploring Primordial Black Holes from the Multiverse with Optical Telescopes (Physical Review Letters). When all else fails, appeal to the multiverse. This attempt hopes to explain one myth by a grander, more implausible myth.

Primordial black holes (PBHs) are a viable candidate for dark matter if the PBH masses are in the currently unconstrained “sublunar” mass range. We revisit the possibility that PBHs were produced by nucleation of false vacuum bubbles during inflation. We show that this scenario can produce a population of PBHs that simultaneously accounts for all dark matter, explains the candidate event in the Subaru Hyper Suprime-Cam (HSC) data, and contains both heavy black holes as observed by LIGO and very heavy seeds of supermassive black holes. We demonstrate with numerical studies that future observations of HSC, as well as other optical surveys, such as LSST, will be able to provide a definitive test for this generic PBH formation mechanism if it is the dominant source of dark matter.

That’s a big if relying on another big if.

Darkmatterites, call back when you have convincing empirical evidence instead of a “scenario” that invokes two grand myths: inflation, which was concocted by Alan Guth to get around the appearance of intelligent design, and the multiverse, where anything that could conceivably happen does happen an infinite number of times. See “Guth Goof” in the Darwin Dictionary.

 

 

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