Hmmm. Anybody else ever notice like I just did that the unseen hand of the material universe, Dark Matter, has a certain nominal consonance with Darth Vader, aka the Dark Lord? Cloaked from view, deploying invisible forces. Take your pick: they rule. (Hmm, answer is yes, as I just looked up. See for just one example this story from nearly four years ago by Ron Cowen back when he was filing about a scoop per week for Science News Magazine).
To start over. The last few days has seen a few news stories on the arcane topic of dark matter and more specifically on the search for ways to detect its presence by ways more direct than gravitational anomalies in galaxies, galactic clusters, and other cosmically large arenas. The popular wisdom among cosmologists is that dark matter, whatever it is, accounts for roughly 85 percent of all matter. Recently users of the Fermi Gamma-Ray Telescope reported (in arXiv, see Grist below, and submitted to Physical Review D) finding in Sgr A*, pronounced Sag A star and meaning the core of our galaxy, a little, distinct excess gamma ray flux. They have explanations for most of the glow, but not all. The leftover is in the 1 to 3 giga-electron-volt range of the spectrum. That fits the specs for an intriguing if hypothetical event's signal: mutual annihilation of similarly hypothetical dark matter particles. Such matter would be densest near a galaxy's core. The nearest one is a sensible place to look.
Two media accounts stand out:
- Quanta Magazine – Natalie Wolchover: Case for Dark Matter Signal Strengthens ; Also distributed by The Guardian in the UK.
- Wired Magazine – Adam Mann: Strange Signal From Galactic Center Is Looking More and More Like Dark Matter ;
Let's start on a side note and with the piece by Wolchover, whose byline has been noted often in the tracker from when she wrote a good deal for LiveScience. She quotes a load of people. She interviewed enough to treat the results as a poll, declaring at one point : "Most of the researchers interviewed for this article said …." Another side note: The people she quotes started off with a Dan followed by a Kavork and a Neal, all guys. But then comes a Jennifer, a Tracy, a Juan, a Kathryn, and an Esra. Four of five in that string: astrophysicists who are women. I was not sure about the Esra at first but the article includes a picture. Female for sure. Then came a John and a Douglas. Still, if I counted right, we have an astrophysics story with four of the nine quoted scientists women. Women among prominent astronomers is nothing really new – Neta Bahcall, Vera Rubin, Margaret Burbidge, and Sandra Faber come to mind without looking anything up. And I am sure that as in many professions astronomers today tell persuasive stories about persistent gender bias. But these in the dark matter story are a lot and that feels significant. Not long ago on the NASW talk listserve I opined on the welcome "estrogentrification" of science writing, suggesting that people seeking an alternative to the actual practice of science are a significant reason that two thirds of newby science reporters have, for a good many years, been women. Wolchover as it happens was heading for a physics PhD at Berkeley when the writing bug bit hard. But there is of course no reason to worry that women cannot as a rule hack the cut-throat and intensely focussed pace needed to excel in science – just read Wolchover's story.
Most important for the ksjtracker's writ, this is a well-researched article. One small indication that Wolchover immersed herself in the literature is that in naming authors of papers she even includes a note that one -a woman not even quoted – was still a grad student when the paper was published a few years ago. You gotta be making a lot of calls and doing searches to notice that kind of thing. Also commendable is that she wrote two stories in one – she includes a few substantial passages on recent detection of gamma rays' little brothers, X-rays, possibly due to so-called sterile neutrinos annihilating one another in places cosmologically far away. From this double discovery flows a conjecture that perhaps both reports are genuine evidence of dark matter, and that dark matter has two or more distinct components. This newly renamed Quanta Magazine (Simons Science News until last July) is doing well to publish such science journalism as this.
Mann's story is different but similarly strong. Its forte is clarity of explanation, including putting in easy terms the subtractive method by which the visible sources of the Milky Way's central gamma ray blob were deducted from the total until just a smidge was left – the putative signature of dark matter annihilation. Mann also puts in a grand caveat – after referring to one of the author's opinion that dark matter fits the data better than anything else, Mann writes "But the universe is vast and there likely remain many unknown objects for astronomers to find." In other words, this is all contingent.
To Mann's piece is appended a long list of reader comments. A good deal of it is huffed-and-puffed drivel coated equally in outrage and incoherent semi-scientific lingo. But one hyperventilating critic makes a good point, skewering Mann for declaring that "dark matter is its own antiparticle." As the reader says, the story should have mentioned that such behavior – I believe it was described notably by the mysteriously vanished physicist Ettore Majorana – is a favorite part of dark matter speculation but does not now merit the verb "is."
Finally, Wolchover's story has just one comment but it is very interesting as well. It is, in whole, "I'm disappointed there's no mention of LHC, or other collider, bounds on the WIMP model. Monojet searches at ATLAS and CMS probably already exclude these low mass WIMPs." That is jargon-heavy. Its meaning is spelled out in a story mentioned on the tracker a short time ago. For ISNS, Charles Q. Choi reported that some laboratory accelerator data suggest lower limits on the mass that a dark energy particle may have. Indeed, one wonders if either Wolchover or Mann asked their sources whether those possible limits bear on the new interpretation of either the gamma ray or X-ray measurements.
(Speaking of Choi, he has out just now and again for ISNS a physics plus astronomy story on a dense topic but written too short: Cosmic Experiment Aims To Close Loophole In Quantum Theory. It is about a topic that Choi visits fairly often – spooky action at a distance or quantum entanglement. This one concerns a proposed, bold test of quantum mechanics. It would run entangled particles through instruments obeying instructions somehow modulated by photons in two different telescopes aimed at quasars so far away in opposite directions they cannot have communicated since the first milli-pico-femto-zillionth of a second after the Big Bang or maybe never ever, certainly well before inflation hurled them forever out of sight of one another. It has to do with a 'free-will loophole." I … do … not … get … it. How, again, does hardware on the telescopes use everlastingly separated quasar photons to fool around with the entangled particles? Choi has courage. He tackles hard stuff. This nut I cannot crack.)
Grist for the Mill: arXiv paper ; UC Irvine (via SpaceRef) Press Release ;
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