Comments of the Week #143: from sunlight to rainbows to the best of AAS

"Life would be tragic if it weren't funny." -Stephen Hawking

Well, the first week of the year is behind us here at Starts With A Bang! For most people, that means struggling to return from a long holiday break, but in the world of astronomy that means we've just come back from an incredible week of science at the annual American Astronomical Society meeting! We've had an abnormally large number of stories as a result, and you'll be treated to a stream of in-depth, cutting edge stories smattered throughout the rest of the month! Here's what we've covered so far:

• Why doesn't Earth's atmosphere turn sunlight into rainbows? (for Ask Ethan),
• Galaxy clusters prove dark matter's existence (for Mostly Mute Monday),
• The foolish optimism of thinking dark matter is about to be detected,
• The surefire way to never find anything new in science,
• Massive Arecibo study subtracts the galaxy; reveals a pristine Universe,
• Distant quasars show that fundamental constants never change,
• Elements of life discovered everywhere in the Milky Way, and
• Cosmic 'spitballs' released from Milky Way's black hole.

There's lots more to come this year, of course, but let's close out the weekend with a grand edition of your comments of the week!

30 Doradus, the brightest star-forming region in our galaxy. Image credit: NASA, ESA, ESO, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S. E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), N. Bastian (Excellence Cluster, Munich), L. Bedin (INAF, Padua), E. Bressert (ESO), P. Crowther (Sheffield), A. de Koter (Amsterdam), C. Evans (UKATC/STFC, Edinburgh), A. Herrero (IAC, Tenerife), N. Langer (AifA, Bonn), I. Platais (JHU) and H. Sana (Amsterdam).

From Anonymous Coward on the intermediate black hole problem: "How does one make a black hole in the thousands to the few tens of thousands of solar masses?"

There are two ways. One is to have a star that forms with a certain metallicity and a mass upwards of a few hundred solar masses. Those black holes will not explode in a supernova, but will directly collapse to a black hole, maintaining 100% of their mass in the process. The merger of only a few of these can get up into the range you're seeking.

The other way is from a substantially large, volatile star cluster, like (potentially) the humongous one in the middle of the Tarantula Nebula: 30 Doradus. There are dozens of stars in here over 50 solar masses, a couple of handfuls over 100 solar masses and even a few that top the 200 solar mass mark. In the earlier, lower-metal Universe, we believe we can have even more massive ones, but the whole point is that these stars will live for only a few million years before they end their lives, giving rise to a black hole. Large mass, compact objects like this have a propensity to merge together, creating the thousand-to-ten-thousand mass black holes you're looking for. That's the theory; the observations have to catch up!

The ultramassive, merging dynamical galaxy cluster Abell 370, with gravitational mass (mostly dark matter) inferred in blue. Image credit: NASA, ESA, D. Harvey (Swiss Federal Institute of Technology), R. Massey (Durham University, UK), the Hubble SM4 ERO Team and ST-ECF.

From John on colliding galaxy clusters 'proving' dark matter's existence, or not: "Sabine has a reply of sorts: backreaction.blogspot.co.il/2017/01/the-bullet-cluster-as-evidence-against.html?m=1"

I was dismayed to see this post from Sabine, as was Richard Easther and a number of other astrophysicists. You might think that you can just simulate the Universe with baryons and cold dark matter, identify where large galaxy clusters are, and see what speeds they ought to collide at. Then you can compare these "mock" Universes with the colliding clusters we actually see, and see if our Universe fits these models or not. That's what the early papers did, claiming, "OMG NO! There's a problem with our cold dark matter Universe!"

But there are a large number of problems with this approach. We don't know how feedback works: the formation of stars, the collapsing of baryons, the growth of galaxies, etc., all affects the structures and profiles on larger scales. Simulations are only just beginning to account for this. We only statistically model these big dark matter haloes, using large-scale correlations, but the haloes we identify are extraordinarily model-dependent. And it is very difficult to translate these simulations, which require the largest scales to do, into smaller, individual observables at the tail end of a distribution. We'd be surprised if we found 100 colliding galaxy clusters like this, but not this one. While some studies claim a "one-in-ten-million" chance of this existing in the Universe, others claim a 1-in-a-thousand or even a-few-in-a-hundred. Saying "this is statistically unlikely" has proven to not be a robust cosmological argument when you're still understanding your models, simulations and the relevant physics at play, and when you only have one Universe to observe. There is a long history of claims like this turning out to be wholly wrong, and Sabine's reporting, unfortunately, is three years out of date on this issue.

The surface magnetic field of an active EMdrive, during the NASA test. Image credit: NASA Spaceflight forums, via Chris Bergin.

From Denier on the EmDrive: "Can you please clarify your stance on the EmDrive? Back in August 2014 in a piece titled ‘How to Fool the World with Bad Science’ you called the EmDrive ‘false information posing as science, eroding the public trust in science itself”. You had a follow-up thought this past month opining that such things, and all reporting on such things should be banned. Your exact words were “Perhaps we have a right to be free from misinformation masquerading as truths”."

Hello, strawman. So there is a way of arguing that I like called steelmanning, where you take the argument someone made exactly as they made it, refute it, and then you yourself look for ways to make that argument stronger. The ones you disagree with; you look for the holes in it and then you plug the holes yourself, and then you argue further even against that, attempting to refute the strongest version of the argument possible. Strawmanning is the opposite, where instead of taking the argument as someone made it, you take a weaker, twisted version that you've made into an absurdity and blow it over, as one would some straw in a moderate wind.

I never said that reporting on misinformation posing as truths should be banned. I said that unscrupulous, misleading, lying or otherwise twisted reporting on such matters should be discouraged or perhaps even punished. I suggested that publishers should band together and create a code of ethics, I suggested that journalists should have an ethical code they abide by, I suggested that a public watchdog group should get involved, and yes, I suggested that perhaps the government should pass a law to regulate this. You and others pointed out that this last option would violate the first amendment, and while I didn't understand that argument, I acquiesced because it's outside of my area of expertise. You then suggested that the "power" one has to fight this should be limited to scrupulous, honest, contextual, nuanced and truthful reporting, which is what I already do my best to do. I pointed out that this isn't working. This is where the argument stands now.

Image credit: World Wrestling Entertainment, via http://wrestlingwithtext.com/tag/german+suplex.

Yes, it's like a World Wrestling Entertainment fight. Someone villainous actor can club the truth over the back of the head with a folding chair, but when the scrupulous hero goes to pick up the folding chair, the referee notices. The hero gets disqualified. And suddenly the villain is victorious. This is what I object to. This is what I resent. You may not see this happening but I do, and many others do as well. Not just with something where there isn't a nefarious actor like the EmDrive, but when there's over fraud involved. You may object to the "make a law" route, and claim it's unconstitutional, and I don't enough know about such matters to evaluate that one way or the other; I have to defer to someone with more expertise. So then the challenge is this: how do we change the way business-as-usual is done to value the correct information of a valid expert over the gain-motivated misinformation of a fraudster? I don't have an answer, apparently, but I submit that you should help me find one. We all should be thinking of how to find one.

The results of last week's Twitter poll. Via https://twitter.com/StartsWithABang/status/752282058420920320?ref_src=t….

From Naked Bunny with a Whip on comment banning: "I love how you make over-the-top proclamations like this repeatedly on a forum where you could be banned with the click of a button, yet haven’t been."

It takes a lot for me to ban somebody. "Haha, you suck, Ethan," isn't going to do it. "I disagree with you and I'm going to twist your words as I do it," isn't going to do it. "You're a dummy, dumb stupid Ethan," won't do it either. The things I have banned people for are repeated offenses of promoting their own theories or ill-informed blogs, trying to sell something, link-spamming the comments section, or one-time offenses of overt hate speech (racism/sexism/anti-gay/anti-semitic slurs) or death/violence threats. All of which I've gotten. That's how we do it here.

Image credit: XENON 100 detector, via the XENON collaboration.

From ketchup on looking for dark matter directly: "it sounds as if today’s dark matter search experiments are the scientific equivalent of the drunk who is looking for his keys under the lamp post – it is not necessarily that he thinks that is where he lost them, it is just the only place he can see."

This is correct! In this sense, we can definitely say (if we're being the most optimistic possible), "2017 could be the year we find dark matter." We can say that because we're still looking, and we're looking in a slightly greater parameter space than we've looked before. That's worth something! But we aren't looking in a significantly new regime, because we don't know how to do that with the apparatuses we have. And so it isn't likely that we'll do it, but it's possible, and so we try. With the full recognition that nature will have to be cooperative with us if we're actually going to find it.

The various constraints on departures of neutrino speed from the speed of light from various experiments. All experiments display upper limits, except for OPERA's spurious positive detection. Image credit: M. Strassler (2011), modified by E. Siegel to include ICARUS and refute the initial OPERA claim.

From Wow on the OPERA faster-than-light neutrino results: "Come on, Ethan, YOU were doing that with the team. *I* was the one saying “Hey, it could be right, and that they grabbed headlines with an early ‘astonishing claim’ doesn’t make them bad”.
If you want to get picky, you weren’t “jumping on them”, you were just angry that they hadn’t checked themselves before printing the story. But that’s still telling them to STFU first, check second, print last."

This is true; I was completely dismissive of the possibility that their neutrinos could actually be traveling faster than light. I was absolutely doing everything I could to look for possible ways that the OPERA results could be explained by mundane, regular, "known" physics and was quite vocal that fantastic claims to the contrary were almost certain to be wrong. Of course, this was based on observed neutrino speed constraints for both higher and lower energy neutrinos, so I think it was well-motivated. I was a bit upset that they had published their findings and released the news to the world quite publicly without finding what turned out to be an internal problem, but in hindsight, my view on the level-of-wrongness of the OPERA collaboration has softened a bit.

Who knows; maybe I'll soften my stance on other perceived wrongdoings in the future as I continue to age?

The alignment of neutral hydrogen (white lines) with the polarization data from the CMB (gradients) is an inexplicable surprise, unless there's an additional galactic foreground. Image credit: Clark et al., Physical Review Letters, Volume 115, Issue 24, id.241302 (2015).

From Mark Thomas on the Verschuur paper and the galactic hydrogen/foreground implications: "Dr. Verschuur knows the Hydrogen maps of the Milky Way better than anyone else on the planet (Since the 1960’s). Dr. Schmelz and Verschuur’s paper should be taken seriously and discussed. Physicist’s at Oxford University were highly critical of Verschuur’s earlier papers on this subtraction of the Milky Way hydrogen maps."

Verschuur has made many discredited claims about hydrogen in the Milky Way over long periods of time. He's also done some very good science. This latest paper is hotly debated, and I had some rather towering figures in the field chastise me for publicizing the work of a poor-quality scientist. But this has passed peer-review in a legitimate journal (ApJ), it makes a sensible, solid argument and it presents data that I believe needs to be taken seriously. It may yet turn out to be wrong, but the paper itself isn't in crazy crackpot land. At least, not that I, the referee, the AAS press office or the USRA could find. Anything else is an ad hominem, and even if it's justified in your mind based on previous examples, the work itself deserves to be evaluated on its own merits.

The particles and forces of the Standard Model. Image credit: Contemporary Physics Education Project / DOE / NSF / LBNL, via http://cpepweb.org/.

From Narad on what makes something fundamental: "Anyway, what’s with characterizing the Particle Data Group electromagnetic constants as fundamental? They have units."

You do realize that dimensionless doesn't need to equal fundamental, and that dimensionful doesn't mean it isn't fundamental? It's all about how you choose to view the Universe. I could say, "the electron charge is fundamental" or "the strength of the electromagnetic interaction is fundamental" or "c, h and G are fundamental," and it's merely a matter of convention. If the Universe were fundamentally different, these constants would be different, and combinations of these constants would be different, too. That we can parametrize them as dimensionless is a nicety, but it isn't a necessity.

Sun-like stars with potentially habitable planets are plentiful, but which ones are inhabited are still unknown. Illustration credit: NASA / Kepler.

From Stephanie Stephenson on an Earth-twin around a Solar Twin: "The type of star required to parent an equivalent planet to our own may be out of reach until we learn the difference between creation and evolution."

We have very good reasons to doubt that this is true. We can observe the spectra, metallicity, color, mass and many other properties of a star like our own. We can detect potentially habitable, Earth-like planets around such stars by multiple, complementary methods. And soon -- as in likely in the first half of this century -- we'll be able to do direct imaging and spectroscopy on these worlds and on their atmospheres, probing for biosignatures. Also, we know the difference between creation and evolution; one puts the conclusion before the evidence and one puts the evidence before the conclusion. This is the critical difference between science and non-science.

This artist’s conception portrays a collection of planet-mass objects that have been flung out of the galactic center at speeds of 20 million miles per hour (10,000 km/s). These cosmic “spitballs” formed from fragments of a star that was shredded by the galaxy’s supermassive black hole. Image credit: Mark A. Garlick/CfA.

And finally, from Sinisa Lazarek on a double-black-hole slingshot idea: "What if we had a binary BH system… which is at just the right distance for a spaceship to be able to grav. assist slingshot in between them? If one BH can slingshot a star or parts of it to 10.000km/s.. then two could probably slingshot a spaceship to something very near the speed of light, no?"

It depends on what you give up! How fast do you fall in; what's your maximum velocity? What's the maximum revolution speeds of the black holes around one another? And are you -- as the star infalling in this system was -- willing to jettison and destroy a large part of your mass in order to "fling" out a much smaller part at higher speeds?

Basically, you can do it, but at your own peril of the tidal forces. If the gravitational force that holds a star together isn't enough to keep it from being torn apart by a black hole, though, I don't like your odds! Thanks for a great week, and see you back here tomorrow for more science and more Starts With A Bang!