Reporting on math

I followed a link to the Quanta article on "the fight to fix symplectic geometry. I didn't know what symplectic geometry was, but the link said this was about the foundations of one field of mathematics. So did the article itself:

The field continued to grow, even as the errors went largely unaddressed. Symplectic geometers simply tried to cordon off the errors and prove what they could without addressing the foundational flaws. Yet the situation eventually became untenable. This was partly because symplectic geometry began to run out of problems that could be solved independently of the foundational issues, but also because, in 2012, a pair of researchers — Dusa McDuff, a prominent symplectic geometer at Barnard College and author of a pair of canonical textbooks in the field, and Katrin Wehrheim, a mathematician now at the University of California, Berkeley — began publishing papers that called attention to the problems, including some in McDuff’s own previous work. Most notably, they raised pointed questions about the accuracy of a difficult, important paper by Kenji Fukaya, a mathematician now at Stony Brook University, and his co-author, Kaoru Ono of Kyoto University, that was first posted in 1996.

If, however, you go on to read the rest of the article, you find (executive summary) that they thought Fukaya's original paper hadn't quite proved what he set out to prove. After some back and forth, and 300 pages of explanation and elaboration by Fukaya, everybody thinks it's OK now.

Not foundational, except that a lot of people were using the techniques Fukaya said were OK. Nor errors, exactly. His proof wasn't complete, but the result looks like it was OK.

I guess writers have to try to make every story exciting. I was going to write more about this, but Lubos Motl already savaged the article, twice. Of course, he tries to make stories exciting in his own way. (If you want a less polemical essay by Motl, try one on Churchill as astrophysicist.)

Every now and then a story really is big news, but the constant overhype wears on me after a while. And that's just in the science section.

Blacksmith

Isaiah wrote of the potter, shaping, reshaping, starting over.

Sometimes it seems as though a different sort of craftsman is at work.

At re-enactment sites or fairs, one booth never seems to lack visitors--including me. The blacksmith's work is fascinating and familiar. Whether is is a scrap iron bar being made into a grass cutter or a bit of rod stock into a pot hook, the cycle is the same--heat, then hammer and bend.

It isn't precisely parallel to our lives. Sometimes the fire is trouble and sometimes what softens us is a coal-bed of love (hotter now than the wild flames we started with). Sometimes the hammer is a crisis, and sometimes the bending comes from day by day little changes.

I'm not what I was, nor remotely who I ought to be. Maybe if I loved more it would go faster. And probably go harder, too.

Gifts

Anybody remember the "Spiritual Gift" sessions? Everybody was encouraged to take the survey, or the class, or whatever, and find out what their spiritual gift was.

I saw this several times. The first time I was pretty young, and thought it was a nice idea, but I already had a pretty fair idea of what I was good at and what my role in church was shaping up to be.

The second time it came around, I pointed out that the program seemed to be just encouraging people to run around saying "Hey, look at my hammer!"

The next few times I had to wax the driveway those nights.

Now there are varieties of gifts, but the same Spirit. And there are varieties of ministries, and the same Lord. There are varieties of effects, but the same God who works all things in all persons.

Maybe we're pushing a rope. What effects do we want, what service will produce those effects, and what gifts are needed in those services?

If God sends another Billy Graham, that seems like a good signal that the church needs a new evangelism program. If somebody has some obviously remarkable gifts that seem to require new modes of service, that's great, but I think most of the time things are less obvious.

Where did the time go?

If you want to spend time on youtube...

"Smarter Every Day" is a fun series of videos about science and engineering and cool stuff (e.g.Tesla coil gun. Does the arrow fly farther when you hold the draw for a moment first? What does a Prince Rupert's Drop look like as it shatters, and why?

I ran across Lindybeige: a reinactor talking about medieval arms and armor and other topics. He speaks both from research and experience with reinacted battles. He's interesting and plausible, though when he leaves his field of expertise and starts talking about (e.g.) holographic tank optics, you get nonsense. His experience is in reinacting battles, and not in urban combat and enforcement. A couple of weapons he deprecated look like they'd be more useful in narrow alleys with nobody beside you than in battle array with buddies around.

And, of course, auto repair videos. I've been watching a bunch of them lately. I'm still not quite sure how they got one piece to come loose so easily; I can't get it to budge.

Scots Irish

I read Born Fighting recently. I didn't post about it right away, because I wanted to think about a question I had. The Scots-Irish were intensely violent not that long ago. They are still one of the more violent white ethnic groups, but their rate has gone down, and other groups are now much more violent. What led to the decline, and are there lessons we can apply elsewhere?

I haven't found out yet if this has been studied, or if we just have the usual "jobs and education" claims without evidence of causality. Olmstead's book suggests that neither was an attractive option.

Music by subtraction

I'd been curious whether one could play all the notes except those for the melody, and still recognize the music. My experiments along those lines were dismal failures, and as AVI reminded me in the last post, you can recognize quite a few songs simply from the rhythm, without notes.

I think I need to find the music for some melodies I don't know, and use a computer to synthesize the "reverse" notes, and try listening to those. One problem is, how do I know that I don't know it unless I listen to it? Maybe I could translate them into one-note pieces, and listen to those, and if I recognize one chuck it and experiment with the rest.

Seems like a good rainy-day exercise.

Music memory

I'm puzzling again about how memory works.

Something about songs makes them easier to remember. Maybe it’s the combination of sound and word; maybe the effective narrative holds it together.

Some ear worms are just fragments of songs playing in loop, so the memory of a song can be chopped up somehow into segments handy for the brain. And I find that sometimes chunks of different verses mingle.

For example, I remembered part of a famous hymn as “Thou Who almighty art, mildly ordainest judgments unsearchable, famine and sword. Bid not Thy wrath in its terror o’ertake us...”

I looked it up. Oops. “God the Omnipotent.” “Thou Who almighty art” looks like an import from a different song, which just happened to have the same rhythm . “Wisely” turned into “mildly:” I’ve no idea why. The “bid not Thy wrath” section is from a different verse. So I assembled this version from a phrase with the same meaning and rhythm, a single-word shift, and chunks of two different verses.

This suggests that I store some songs in the form of chunks and a set of links, and link the chunks together on demand. It looks like both rhythm and words serve as keys. Meaning may not be a reliable key, but it does get used.

The instrumental music playing in Urgent Care(*) included a song I’d not heard since the 70’s, and I realized I couldn’t recall more than a few lines. The melody I could reconstruct easily. (I don’t usually mix melodies together—in contrast to lyrics--though now and then I do.)

When we got home I went to look for the song--and kept coming up blank.

Executive summary: the tune was the Airport love theme, which is almost entirely instrumental, with only a couple of lines sung at the beginning and end about the winds of chance. My brain expected the rest of the words to be there, and did its best (modulo substituting “restless winds” for “gentle winds”). Missing part was especially irritating.

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(*) It turns out a Mansfield bar doesn’t protect car tops when the trailer jackknifes. She had no apparent injuries, fortunately.

Somebody's been reading classics?

"Severities should be dealt out all at once, so that their suddenness may give less offense; benefits should be conferred gradually, and in that way they will taste better."

Niccolo Machiavelli

Not a good sign

The drug combination was unable to cure four patients, who had all visited Africa, in early signs the (malaria) parasite is evolving resistance.

When the disease reappeared, they were brought back in and treated with other drugs (atovaquone/proguanil, artesunate and doxycycline, or quinine + doxycyline). So there's not an emergency. But...

Parasite isolates, all of African origin, harboured variants at some candidate resistance loci. No evidence of pfk13-mediated artemisinin resistance was found. Vigilance for signs of unsatisfactory antimalarial efficacy among imported cases of malaria is recommended.

LHC robots

Symmetry has an article about the robots of the LCH.

As you might expect, the subterranean tunnel which houses the LHC is not always the friendliest place for human visitors.

“The LHC contains 120 tons of liquid helium kept at 1.9 Kelvin,” says Ron Suykerbuyk, an LHC operator. “This cooling system is used to keep the electromagnets in super conducting state capable of carrying up to 13,000 Amps of current through its wires. Even with all the safety systems we have in place, we prefer to limit our underground access when the cryogenic systems are on”.

Unfriendly is a bit of an understatement. When the magnet quenched the resulting explosion shoved a 35 t dipole magnet into its neighbor, and the escaping liquid helium allegedly condensed the air.

Near the collision points the radiation levels are pretty doggone high. I'm not sure robots would survive in the collision halls--for that matter I don't know if they can go in. And you have to worry about little things like the fringe of the magnetic field for CMS--high enough to mean that power supplies have to be kept far away from the electronic devices they power--which costs some DC power loss.

So, meet TIM. Except the picture at the top of the article isn't of TIM ("the Train Inspection Monorail. TIM is a chain of wagons, sensors and cameras that snake along a track bolted to the LHC tunnel’s ceiling"). The video is, though.

Davila

David Warren posted this link to a translation of a short work by a Colombian I'd never heard of before, on the subject of The Authentic Reactionary. "If the progressive casts himself into the future, and the conservative into the past, the reactionary does not measure his anxieties with the history of yesterday or with the history of tomorrow."

Political postings

In the run-up to the elections in 2008, I came to the conclusion that commenting on politics was bad for my soul. The temptation to despise seemed overwhelming. During the past 8 years I've more or less held to my resolution to back off. And when all's said and done, much that's said never changes any minds anyway--sometimes the values and presuppositions are too different.

Is liberty valuable, and if so what is its scope? For that matter, what is it? Not a question people like to discuss, but an illuminating one...

The tribe that believes that people are perfectible doesn't generally value liberty very highly--probably for the same sort of reasons that kings punished heretics. Monarchs owed it to their subjects to protect them from those who could mislead them into hell--or, these days, from being perfected subjects with all traces of evil ideas scrubbed away.

Naturally that protection requires more and more centralization, and more and more micromanaging, and more and more careful parsing of anything that might smack of subtle evil ideas (an analysis that apparently only certain people are capable of--and as with The Force, they must trust their feelings).

No, an essay on "why you should deliberate carefully when trying to overhaul the health care system for a nation" is not going to change any minds across that kind of divide. Nor are those impatient to undo the damage going to listen to an essay about "why there needs to be some bandaging to let things grow back."

I'm probably not going to be commenting much during this administration either.

Pulsars

Pulsars are neutron stars whose EM radiation (light, radio waves, gamma rays) seem to blink or pulse. This is related to how they rotate (and their rotation can be measured to be slowing down). Because the magnetic poles don't usually line up with the axis of rotation, sometimes the pole is pointed more in our direction, sometimes less so--and it seems to pulse.

But what they radiate seems to be all over the map. Sometimes they radiate gammas but not radio, sometimes radio but not gammas, sometimes both. Why? Maybe it has to do with which way the star is pointed relative to us.

based on these observations, Geminga’s magnetic poles appear to be oriented at the top and bottom of the neutron star from our point of view, which also align with its spin poles. Because these areas are where a pulsar’s radio emission should originate, it makes sense that no radio waves are detected. The pulsar’s gamma rays, however, are created over a larger area at higher altitudes, causing them to sweep out over a larger area of the sky and making them detectable from Earth.

It makes sense. Verifying that would be kind of hard--we'd have to have a clear idea of how far from the rotational axis the magnetic poles point, and then try to correlate that with the ratio of gamma to radio. But I've no idea how to measure that angle. You could get some notion of the direction of the axis of rotation from the jets of stuff shot away from it (you'd measure the doppler shifts of each of the two lobes to try to pin down their speed and direction), but measuring the magnetic field direction sounds hard. Polarization of light would be going this way and that with the moving field, and I'm not sure you could tell that from randomness.

Differences

Pick one:
NASA has approved a mission to explore 16 Psyche, an iron-rich asteroid whose contents are said to be worth over 100-thousand times the value of the entire world economy.

Or
"Psyche is almost certainly an iron-nickel alloy asteroid, possibly formed after a larger body, like a dwarf planet, had its mantle stripped away from a violent collision with another asteroid. So, Psyche is probably the exposed core of a small planet," Bercovici said.

Do you want to pull your hair out when you see "gee wow" reporting like this? "Psyche is an asteroid with a diameter in excess of 125 miles, about the same size of the state of Massachusetts, and is almost entirely composed of iron and nickel. The abundance of these metals gives the asteroid's contents an estimated worth of a staggering \$10 quintillion — that is a one, followed by 19 zeros. Comparatively speaking, the world economy is estimated to be worth just under \$74 trillion. Psyche's contents are worth approximately 130,000 times as much as every single human industry put together." Transportation costs aside, supply and demand considerations make complete nonsense of this sort of calculation. You're supposed to get excited about big numbers, even when they don't make any sense.

If Psyche is indeed the remains of a much bigger object, that's more exciting. The problem is, I don't know if explorations would tell us much about a long-gone planetary crash. So it may just be exciting in a T-Rex skeleton sort of way. (The Field Museum's Sue exhibit has a case with some extra "belly bones" and the confession that nobody knows where they fit.)

Maybe the composition and structure can tell us about how planetary cores form--though the details of the composition will surely have been different from Earth's. Unfortunately the probe is supposed to launch in 2023 and arrive in 2030. A bit of a wait.

Paris streets

I saw a report today from the Mirror saying that French told not to fear wolves roaming Paris streets as 'they only eat four-legged animals'.

That sort of encouragement doesn't comfort. Even if Parisians were OK with wolves that only ate pets, wolves still threaten everybody.

But who else is on the streets? I don't think wolves stand a chance. People can be very thorough when dealing with threats.

Merging black holes

We all remember the LIGO discovery: a pair of black holes merging to produce a beautiful gravity wave signal. It was followed shortly thereafter by a smaller pair producing not-so-nice a signal, but good enough.

LIGO didn't take data very long, but got 2 signals in only a few months. (They're starting up again.)

From that rate, Ioka et al estimated how many mergers there have been in our galaxy so far (mostly much smaller ones, and obviously we weren't looking at the time--weren't here for most of that time). (Basically they figure that if LIGO detected really big ones at the range they did, it would have missed the many more smaller ones in the same volume, because it wasn't sensitive enough.)

When two orbiting bodies like that merge, the result has fantastic angular momentum. If you spin a bicycle wheel and grab it, you know that it "doesn't like" being stopped. Imagine if the bicycle wheel were made of lead, and spinning that fast. You might break your hand trying to stop it. Now spin it up faster, and faster. There's a lot of energy in that thing now. There's unimaginably more in the black hole you get from merging two others.

The first direct detections of gravitational waves (GWs) from black hole (BH) mergers, GW150914, GW151226 and LVT151012, give a robust lower limit ∼70000 on the number of merged, highly-spinning BHs in our Galaxy. The total spin energy is comparable to all the kinetic energy of supernovae that ever happened in our Galaxy.

They go on to estimate what kind of activity you can get from interstellar gas falling into these things, which is of interest to people trying to study cosmic rays (like IceCube).

Let me emphasize that most of these black holes aren't very big--only a few solar masses. Still, 70,000 merged black holes in our galaxy--wow.

Of course there are some assumptions that go into that--like assuming that the rate of black hole merger is essentially constant in time. I'm not sure that's realistic. And they may have the distribution of the rate of production of different size black holes wrong. But nobody found any showstopper problems with it at the meeting today.

Appendix

I've never been confident in the claim that the appendix is a useless vestigial organ. Everything else is doing something, sometimes many somethings at once. Why waste energy growing something useless? Maybe it is a bacteria reservoir?

They discovered that the appendix has evolved independently in several mammal lineages, over 30 separate times, and almost never disappears from a lineage once it has appeared. This suggests that the appendix likely serves an adaptive purpose.

Dust never sleeps

Or, when it does, the ultraviolet wakes it up.

On the Moon, and presumably any airless body, UV-stimulated emission and re-capture of electrons in the cavities left between dust grains can charge the dust, and the negatively charged particles can be levitated by electrostatic repulsion.

We have recorded micron-sized insulating dust particles jumping to several centimeters high with an initial speed of ~0.6 m/s under ultraviolet illumination or exposure to plasmas, resulting in an equivalent height of ~0.11 m on the lunar surface that is comparable to the height of the so-called lunar horizon glow.

Since there's no reason it should jump straight up, a particle will fall down again some distance from its original location. So dust will spread.

This is only significant in airless regions, so don't blame the state of the bookcase on UV light.

Mark your calendars

Molnar et al are predicting that a binary star system will merge and explode in 2022. If true, Cygnus will look a little funny for a couple of years.

The eclipses of one star by the other are coming faster and faster, and if V1309 is anything to go by the pair should spiral in and merge in a moderately dramatic way in about 5 years.

If this event is anything like the 2008 explosion, it’ll take about six months to rise to its full brightness — 10,000 times greater than the brightness of the original. When it comes to space phenomena, it can sometimes be hard to tell what big numbers are actually as impressive as they sound and which are not actually big at all relative to, you know, the scale of the universe. This is the former. It will mean a noticeable change in the brightness of the night sky.

And if it takes 6 months to grow, the weather shouldn't get in the way, as it tends to with things like solar eclipses and comets and auroras.

Pithy wisdom and slogans

Back in 2013 I wrote about proverbs that "I don't hear these much, though perhaps I don't travel in the right circles, and I suspect we suffer for it." Since then I've been looking for places where old proverbs, or what used-to-be familiar scripture would fit in.

I'm surprised that I didn't hear anyone cite "Better the devil you know than the devil you don't" about the last presidential election. It was certainly one of the major themes.

You hear plenty of slogans and phrases encapsulating some political or social ideas, but that's not quite the same thing. The slogans anticipate, while the proverbs react to, classes of situations. For example "The people united will never be defeated" is an aspirational slogan (and piano composition): history is chock-a-block with counterexamples and compromises that only vaguely resemble victory. "He who slaughters a beast does not hesitate about skinning it," on the other hand, warns the wishful thinkers in every age. We hear "Liberty, Equality, Fraternity," or "no justice, no peace"--both aspirational (since the latter implies that there will be peace once there is justice). But "A camel never sees its own hump." You know people like that.

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I like this one. Albanian: "Fire, water and government know nothing of mercy." And this "A benevolent man should allow a few faults in himself to keep his friends in countenance."