Stacy McGaugh Profile picture
You can lead a theorist to data, but you can’t make him think.
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Aug 28, 2018 15 tweets 4 min read
What we have here is a failure to communicate. Over and over I see statements from esteemed colleagues - genuinely brilliant people - that are simply incorrect, for simple lack of fact checking. Like “using only two out of 10 pieces” of evidence. How does one count? Or “MOND doesn’t and dark matter does.” Does what, exactly?
Aug 19, 2018 4 tweets 1 min read
Strange choice of headline for a mission that was planned to run for 3 months but ran successfully for 14 years. This is a skilled and subtle form of propaganda. By putting the price tag up front (how is this relevant to the story?) the immediate and natural reaction is to scoff “What a waste!” when by the standards of space missions this was incredibly successful and long-lived.
Aug 19, 2018 6 tweets 2 min read
Minor astronomical mystery last night. Looked out just before bed & noticed the first quarter moon was... dimmer than usual. This was pronounced enough that I went out to look. Indeed. Even a slight shade of red. Also fewer stars than usual. But no clouds in the sky, nor cirrus. Woke up this morning; still no clouds. The color of the sky seemed off though, and the sun a bit orangish even once well above the horizon. What the heck? Then I remembered all the wildfires in the west, and decided to look up a smoke map at @NOAA
Jul 31, 2018 8 tweets 2 min read
Came across 1954 classic “Them” on TCM. Apparently standard issue for New Mexico State police back then included sub-machine guns. Hollywood hype? Or just ahead of their time? I mean, you meet a freakish giant ant in the desert. Pistol fire doesn’t phase it. So the state trooper runs back to the patrol car for extra firepower. Smart move. I’m expecting a shotgun, maybe a rifle. But dude comes back with a sub-machine gun. WHY is that in the trunk?
Jul 27, 2018 16 tweets 4 min read
Oh, Ethan. There you go again. Ethan Siegel has made it clear that he hated MOND. Over the years he has made it a personal crusade to persecute the heretics who dare speak of such things. Because nothing says scientific rationality like as hominem attacks.

Mostly I ignore him.

Jul 23, 2018 17 tweets 3 min read
I like the starting point: “collapse [at] z<10+” The “+” makes it. Collapse could happen any time. Redshift less than 10. Or redshift greater than 10. Whenever.

I really empathize with Simon here. This is a problem I’ve often faced as an observer. How do I express the predictions of a theory that makes no [agreed] prediction?
Jul 20, 2018 4 tweets 1 min read
Shocked Conservative Learns Obama Doesn’t Hate White People - New York Magazine… Nails it:
Jun 28, 2018 4 tweets 2 min read
I know a number of serious dark matter experimentalist. They’re really talented scientists. It is amazing the progress they’ve made in increasing the sensitivity of DM detection experiments, especially those based on Noble gases like Xenon. fabulous work. But they have no result The common wisdom for why the physics Nobel committee never recognized Vera Rubin for discovering dark matter was that this was such an outlandish proposition that it had to be confirmed by laboratory detection. That may not have been the only reason, but that was part of it.
Jun 19, 2018 5 tweets 2 min read
Here is a histogram of characteristic accelerations from the SPARC data (our data fit by For each galaxy, g+=x*Vf^4/(G*M). The range of the x-axis is set to match their Fig. 1. No fitting of any sort has been done. The scale a0 is in the data. Vf is the flat rotation velocity. M is the baryonic mass - the sum of stars & gas assuming fixed M/L for all galaxies. G is Newton’s constant. X=0.8 accounts for the geometry of disk galaxies (they’re not spherical cows and we can tell. See Binney & Tremaine). There at no knobs.
Jun 18, 2018 6 tweets 2 min read
Here’s the cumulative distribution of chi^2 from Pengfei’s paper. Red line is a fixed RAR, basically equivalent to MOND. The other lines let g+ vary with Gaussian or flat priors. One gains nothing meaningful by letting g+ vary. Note that this distribution does not look right for chi^2. There are too many “bad” fits (high chi^2). That’s true. But it doesn’t help to vary g+ or anything else. Dark halo fits have a CDF with the same shape. One can’t best-fit one’s way into a sensible CDF. So what’s up??
Jun 14, 2018 4 tweets 2 min read
New blog post summarizing recent work by grad student Pengfei Li.… The scientific version of the paper is in press at A&A; you can get the preprint at
Jun 13, 2018 7 tweets 2 min read
I never cease to be amazed at the human capacity for self-deception.… The precursor of the radial acceleration relation, the mass discrepancy-acceleration relation, has been known since the previous century. In 2004, I provided a general version for simulators to shoot at:…. The response was deafening silence.
Apr 15, 2018 15 tweets 4 min read
You must be thinking of the badly outdated “falling” rotation curve of DDO 154. That wasn’t very persuasive at the time, and was shown to be incorrect by THINGS a decade ago. DDO 154 has M*<Mgas and is well for by MOND with essentially zero freedom. This is a microcosm of everything wrong with science today. We don’t like MOND, so dismiss it the instant one scrap of dodgy data looks slightly out of place (eg DF2). But we like CDM, so spot it endless amounts of special pleading. The bullet cluster is a good example of that.
Feb 28, 2018 21 tweets 5 min read
Really awesome detection of 21cm absorption in the early universe (z=17). I’m very impressed that this measurement can be made. Surprising result - to most cosmologists - is how strong it is - about 2.5x stronger than expected in LCDM. This does not surprise me. It is exactly the kind of test I proposed 20 years ago based on the cosmic baryon fraction. If LCDM is correct, fb=0.16. If dark matter is a chimera indicative of some modified gravity, then really fb=1.…
Feb 11, 2018 19 tweets 4 min read
Interesting perspective. It is now over 30 years since I published my first referred paper “An investigation of the efficiencies of various buffer gases in Na-Xe spin exchange”, which has never been cited, even by me.… It did perhaps contribute in a tiny way to making the world a better place as an incremental part of a larger project that ultimately led to useful medical imaging technology. Not that I appreciated that potential at the time; we were just trying to figure out how things worked.