Wednesday, November 22, 2017

Neutrino cross sections

It turns out to be very convenient to describe the rate at which particles interact with each other with an "effective area". Think about it a moment--if you two rocks at each other, the wider the target rock is, the more likely they'll hit. And when you work out the dimensions for particle interaction rates, area=="cross section" is what you wind up with.

IceCube just announced its measurement of cross sections for high energy neutrinos interacting with ordinary nucleons. Nobody has been able to measure the rate for energies this high before--and the result looks pretty consistent with predictions.

That rules out some oddball theories--like leptoquark models. Leptoquarks turn up as a consequence of some theoretical models, and every now and then some unexpected signal excess spurs new interest.

You will probably have heard that neutrinos zip right through you without interacting--that you never notice them and never will. That's true for the most common varieties from ordinary radioactive decay. But higher energy neutrinos (very rare) interact more strongly, until at the level discussed in this paper, it is possible to tell the shadow of the Earth's core from the shadow of its mantle--with enough events. They're not quite so "ghostly" at these energies.

No, I am not on the author list

Monday, November 20, 2017


Granted that Western harmony is one of the great accomplishments of Western Civ: you can't please everybody at the same time.

(bass-baritone who does OK if somebody else sets the key and the music doesn't go too high)
I don't think I want to be a cello. Even though they do sound very nice.

Friday, November 17, 2017

Side note on a grim story

Indonesia is forcing pagan tribes to convert to Muhammadanism. The excuse is that they can't get birth certificates (and therefore schooling), unless they adhere to one of the recognized religions. They're not happy about it. "There is no compulsion in religion" is once again more honored in the breech than the observance.

One novel bit about the story was the relationships of the tribesmen to their Muslim neighbors. The tribe described is nomadic:

"We have no space to live. We are always told we are nomadic people with no religion, no culture," he told me.

"Our religion is not respected. The government is always insisting that we convert and live in houses in one place. We can't do that. Our way of life is not like that."

And there are sources of friction:

The officer, Budi Jayapura, took me aside to check my documents and said: "We need to watch over them.

"They don't understand the concept of stealing. They say the fruit grew by itself on the tree so it can be taken, but it was planted by someone. Maybe in their belief system it is OK, but not in our society."

The fact that they hunt and eat wild pigs also creates social tensions, he added.

"This is a Muslim community. If they see the pig's blood and the leftover bits, they are disturbed," the officer explained.

What is taboo, or haram, for the Orang Rimba directly contrasts with what Muslims eat, explains Mr Manurung.

"Orang Rimba will not eat domesticated animals such as chickens, cows or sheep. They think it's a form of betrayal. You feed the animal, and when it gets fat you eat it. The fair thing to do is to fight. Whoever wins can eat the loser."

I read of a visit to an Amazon tribe, where people hunted and ate every sort of animal, but if somebody brought it into the village and treated it like a pet, nobody would harm it.


Guy Middleton wrote: Do civilisations collapse? I suppose he wants to invoke Betteridge's law of headlines, and the thrust of his essay is "no." A lot of things remained after the "collapse," not least of which are the people and many aspects of the culture.

It's worth having a look at, for reminders of how complicated changes can actually be. But he overstates things. If you lose the "critical mass" of engineers and craftmen, certain things that once were part of the culture decay and a society may never get them back again. OK, cool--you still speak sort of latin and like garum. But the aqueducts in your valley broke and you don't have running water anymore--no more socializing in bathhouses. Your culture changes.

Minting money

This morning an amusing little report circulated that one can buy a cypto-currency mining system that doubles as a space heater. Clever--take a feature that tends to be a nuisance, especially in consumer-grade computers--the high power requirements of the GPU(*)s used in the calculations that go into "crypto-currency mining," and spin it as a feature--the waste heat can heat your room! With 8 GPUs packed into that small a volume the water heat transfer system had better work well or you can set things on fire. That happened with some collaborators of ours in Maryland.

The whole crypto-currency business reminds me of the gold-rush folks. They looked to get rich by increasing the quantity of symbols of value--but not creating anything particularly valuable themselves. Thought experiment: suppose your country found boatloads of silver and gold (we won't go into details about how they collected it), and brought it back. Now you have the wherewithal to import more stuff, and you need to import--because, funny thing, having twice as many doubloons doesn't automatically double the size of your local industry. In fact it's simply apt to double the prices. Lots more gold, but not necessarily more stuff.

In Dawn Treader Lewis never bothered to explain why a lake that turned things to gold would be bad--except that people got greedy. Too bad, it would have been a one-liner.

Wednesday, November 15, 2017


One of the comments at Maggie's Farm reminded me of some experiments Richard Feynman did with himself: he could count and read, but not count and talk. "... when Feynman told mathematician John Tukey about this, Tukey could do the reverse — talk but not read. The reason was that Feynman would talk to himself in his head, while Tukey would see an image of a clock ticking over. Feynmann suggests this could be because people think differently".

The author of the article suggests that the brain has "modules" like a "sketch pad" or a "phonological module" for words and sounds.

I don't know about how other people use visual thinking in math, but I find that I often do. For example, matrix multiplication I visualize as an action. (I should redo this to slow it down). When I try to figure out the framework for a problem I draw pictures. Equations are partly sentences and partly blocks like pictures.

FWIW, I generally read by "see and say" because I'm already trained to spot the blocks in English words. Sometimes I scan too quickly, and hilarity usually ensues. But I learned phonetically. And when I hit non-English words, I work phonetically. If I have time. Train stops in Germany were a nuisance. The name was often half a block long, and I couldn't read it fast enough--so I read the first and last chunks of the name and hoped that was unique. Problem is, the last chunk was usually "strasse."

Crab bucket

"Deaf singer Mandy Harvey made headlines around the world after being put straight through to the finals of America's Got Talent. But when she first took to the stage, she received death threats from within the deaf community for promoting a "hearing" activity."

I've heard unpleasant things about Gallaudet University too. There's something very nasty about denying reality for the sake of your pride. They pay a weird homage to the very thing they ought to fight--the notion that someone with fewer skills is inferior. Instead of denying that lie, they implicitly accept it and claim that their skills and culture are equal.

"You are not your disability!" I've preached that, though I try not to be explicit about it. People get tired of hearing the same things. But it sure beats "I am my disability, and you are too, and you'd better get with my program."

New wine in classic wineskins

I understand Amazon wants to make more Lord of the Rings-based movies: prequels, I gather.

If they use existing characters, even peripheral, in a prequel, the story gets cramped. If they use new ones, it is more of a "in the universe of LoTR story," but likely without an equivalent story-teller behind them. I haven't heard any enthusiasm for working from the Silmarilion.

I suspect I won’t be investing in downloads.

But... Do you remember the stir when HarperCollins announced the plan to create new Narnia novels?

I’d pretty much forgotten about that—the article above, and several like it, date to 2001. I thought I’d heard a peep or two more recently than 16 years ago, but that may have been temporal foreshortening again.

They have coloring books, and shortened versions: told for younger audiences, and this: ”Based on characters originally featured in C. S. Lewis’s The Chronicles of Narnia, The Giant Surprise is a brand new Narnia adventure story about Marshwiggles, giants, and mice for young children. Lally, a small wigglet, and her Uncle Puddleglum undertake a hair-raising rescue of their mice friends, before they become a giant’s supper.”

I wonder if HarperCollins quietly shelved the “new novels.”

Tuesday, November 14, 2017


We've had quite the uptick in drive-by shootings in the Madison area--mostly non-fatal, fortunately. Today's battle between two cars hit a third car and a nearby house.

I've noticed a lot of defaced license plates lately. Not weathering and fading (as in the last Wisconsin plate design fiasco), but scraped and dented. O(1%) of the cars I see are hard to read the plates on.

Maybe this is a new vandalism fad. That would be the best possibility.

UPDATE. O(1%) means of the order of 1%. Give or take a little.

The pilot in our Wednesday Bible study suggested that the defacement might be to foil the toll cameras.

Sunday, November 12, 2017


I'm a bit conflicted. Nobody believes the casting couch ever went away, and I'm content to believe that the overwhelming majority of the accusations are true, or at least largely so. What facts do manage to leak out past the PR over the years don't inspire confidence in the moral fiber of Hollywood folks, and sometimes the PR itself is telling.

But I have to give the devil his due. It is easy to make an accusation in this atmosphere, especially if it is old enough or vague enough to be un-actionable. After all, if your accusation goes to court, you might get cross-examined. Hollywood is a famously backstabbing place, and if a friend of a friend puts your competitor in a bad light, you might be generously grateful.

So while I hope this shakes out some "bad actors" who think fame or power entitles them, I also hope we take care to vet the accusers too.

Defending churches

Several local worship centers (including a Sikh temple) have decided to have guards. Attacks happen from time to time, and threats sometimes look serious.

Guards or not? I figure I'd rather die in church than in a hospital, but when you recall that the children are at risk too the picture changes a bit--we have an obligation to protect.

So far the odds are pretty good, and I'm not concerned.

Am I naive? I'm not in administration, and I don't see the threats. Our church has a volunteer team keeping an eye on things, but not armed with anything more lethal than a cell phone. We put that in place a few years ago when a nut case interrupted a service. High Point's board is going to vote on whether to have undercover guards--I'm curious about what they'll decide.

Friday, November 10, 2017

Peaceable kingdom

England in the 1600's isn't famous for being a nice time and place to live. But the article says it wasn't as bad as we think. "but the state was not simply stringing people up for occasional acts of petty theft. Quite often, judges and juries deliberately perjured themselves to ensure convicted thieves escaped the noose, usually by undervaluing goods stolen."

Homicide rates dropped over the century (in Kent from 5-6 per 100,000 to 3.6; in from 8-12 to 2 per 100,000). Pinker likes the idea that a strong central government means lower homicide rates--I suspect that you don't get a strong central government if the crime rate is too high.

Selfishness and Charity

David Warren starts off with: "I think that if the “natural man” would vote consistently in his own interest, and by extension in that of his close family, the world would get along tickety-boo."

He doesn't expand much on that, unfortunately. I've suspected for some time that if groups were a little clearer about their interests, there might be fewer and not more conflicts. Proving that would take a lot of study and work with counter-factuals, and I've not world enough or time. But it doesn't take much effort to think of conflicts that started with exaggerated claims and fears. Others were and are unavoidable.

His main point is about spite and charity: charity deals with specifics. "The point I make is on behalf of reality. One’s neighbour — and even in this last instance a brute animal, who could have eaten me were she much larger and in better shape — is a real thing. Insofar as our charity is real, it is directed to real things. Insofar as we are “friends to humanity,” or “friends to the poor,” or “social justice warriors,” we are putting on a ludicrous show, in which spite adopts a pretence of charity."

Tuesday, November 07, 2017


Lubos Motl has a post about the naivete of physicists:
Nima Arkani-Hamed, a top Western official in the Mao collider, sort of "courageously" says that if the tanks came to the Chinese streets again, he would probably join some local protests. His father had some "disagreement" with the Khomeini regime in Iran but Nima himself doesn't really get the evil of totalitarian systems, I think after many discussions with him. As Cheng nicely says about Nima's superficial response:
But his hypothesis, well-intentioned as it was, reveals a deeply simplistic, caricatured understanding of state oppression. True terror and totalitarian control come after the tanks have left the square, when blood is wiped off the streets, the history books, and the people’s collective consciousness, when a date becomes taboo, and when a simple question confirming the existence of the Party office exposes the Achilles’ heel of a grand project.
Exactly. Totalitarianism isn't about some cool scenes with tanks and blood in the street – and Nima's cool but totally superficial and symbolic "no" to such spectacular events. The true muscles of the totalitarian machinery only start to act after the tanks and blood are removed from the sidewalks (the same is true for the German and Soviet tanks in Prague in 1939 and 1968, too). The employees are being ideologically filtered, fired, or arrested, the history is often being rewritten..
Many of my colleagues, Western or Chinese, asked me about my priorities and whether I cared more about physics or human rights, as if these pursuits are mutually exclusive.
And that question is easily used to dispose of the "incorrect" people. If you say rights matter more, you aren't dedicated enough, and if you say physics--don't complain. You are there to be used.

(Lubos is Czech, and grew up under Communism.)


I've heard quite a bit about fan disgust and lower sales and so forth, with counter arguments that there are too many broadcast games, which saturated the market. I'm not plugged into the fan zone, and in any event my observations wouldn't be representative of the broader market.

I thought one simple way to test for fan annoyance is to monitor season ticket sales. But if this article is correct, brokers buy a huge fraction of the season tickets, so any measurement will be indirect. Better than nothing, though.

Computers make it all better

The Navy issued its report the the McCain collision.
Commander Alfredo J. Sanchez, "noticed the Helmsman having difficulty maintaining course while also adjusting the throttles for speed control." Sanchez ordered the watch team to split the responsibilities for steering and speed control, shifting control of the throttle to another watchstander's station. ...

However, instead of switching just throttle control to the Lee Helm station, the Helmsman accidentally switched all control to the Lee Helm station. When that happened, the ship's rudder automatically moved to its default position (centerline). The helmsman had been steering slightly to the right. ...

At this point, everyone on the bridge thought there had been a loss of steering. In the commotion that ensued, the commanding officer and bridge crew lost track of what was going on around them.

And there's more.

I suppose that sort of SNAFU is the default for militaries. If I read my history correctly.

Saturday, November 04, 2017

A newsreel from the other side.

You're probably seen "The Longest Day." The Germans made their own newsreel of the activities. They had a smaller pool of actions to draw from--and I think I see the same tank a couple of times.

Friday, November 03, 2017

Tired of your sin?

I found this cover of "The Church of Your Choice" by Dan McBride. The sound quality is quite mediocre.
Church of Your Choice: (Some of us are old enough to remember the slogan.)

"If you're tired of your sin, then we'll welcome you in. If you're not, you'll still feel right at home."

We'd all love for evangelism to mean just being winsome and attracting people to Christ. I'm perhaps a bit curmudgeonly to be adequately winsome, but it's still an easier goal than trying to be prophetic. And it's more pleasant to think we're all "close enough."

But we know what Jesus said about division, and about the world hating him and therefore hating his followers. And it isn't hard to recall people whose sins are pretty dramatic in our eyes, and who really ought to repent.

So how does one manage to be both accurate and winsome? Jesus said to welcome the children, who generally aren't motivated by a hunger for forgiveness. But he discouraged people who weren't "counting the cost."

Nobody said it was easy... Probably one big first step is not to act as though we've "arrived." (There are two kinds of Christians: those who struggle with besetting sins and those who've given up.)

Thursday, November 02, 2017


I don't remember where I read the rule that "A free man is one who can bind himself." He can bind himself to a wife and to the still unknown children who follow. He can promise to work for someone. He can make an implicit commitment to tend his farm; feed and care for his livestock. Or he commits to solve a problem or write a book. Some commitments are short term, others life-long and extremely open-ended.

Freedom seems less like a status and more like a coin to invest. The one who never binds himself never shows fruit.

Lone wolves

It seems popular to describe Islamist terrorists as "lone wolves," even when there's evidence for a network.

Perhaps the spokescritters-that-be have been sternly told not to divulge anything that might reveal how much we know about those networks. That seems the nicer hypothesis. Maybe it's true.

Alternatively, they may be trying hard to keep Americans from blaming Muslims in general for the incidents of fourth generation warfare. If so, I believe they are mistaken.

If the terrorists are guided by a network, the network can be tracked, understood, and selectively attacked. Lone wolves who spontaneously decide to become enemies can't be tracked. Dealing with them involves much less selective means.

A network is separable from the Muslim community: Muslim with associations = enemy, Muslim without = ordinary. If the model is "spontaneous conversion to enemy," this changes the mapping: Muslim=x% chance of being an enemy simply because he/she is Muslim. Maybe that's actually true, but there are some hints that it isn't.

If the folks in charge want Americans to not blame Muslims, I think they should steer away from the lone wolf narrative, and concentrate on the associations. (Unless they're trying to hide how much we do know.)

Tuesday, October 31, 2017

Dark Matter Day

I have been informed that today is Dark Matter Day, and that I am to circulate these videos:

We search for Dark Matter in IceCube on the assumption that it is made of particles that interact with neutrinos.

It doesn't interact with photons (dark matter particles have no charge: that's what makes them dark) nor with baryonic matter (nuclei), and all we seem to get are limits on its interaction with W and Z (weak interaction--related to radioactive nuclear decay). Since it seems much too odd that we should get two completely non-interacting types of matter in a Big Bang, that just leaves neutrinos for them to interact with. And maybe dark matter interacts with W and Z after all, which would give particles that would decay in turn, which should also give some neutrinos.

Anyhow, if the dark matter particle is unstable, it can decay into a couple of neutrinos. If there are several species of dark matter particle, heavier ones might decay into a couple of neutrinos and a lighter type of dark matter particle. Or they could fuse to make neutrinos. Anyhow, look for neutrinos. Which, happily enough, is what IceCube is designed to do.

So if you see an extra number of high energy neutrinos coming from places where you expect dark matter to accumulate--inside stars, or at the center of galaxies--you might be seeing neutrinos from dark matter particles decaying/fusing. That would be very interesting, and could give you some estimate of just how massive these dark matter particles might be.

Of course if the dark matter particles are very light, they won't accumulate in stars the way you expect(*), plus the number of low energy neutrinos from cosmic ray showers in Earth's atmosphere will probably drown out your signal. (Low mass dark matter would decay to low energy neutrinos.) So the assumptions matter.

Also have a look at the search for sterile neutrinos video. Neutrinos are hard to study...

(*) The cloud of dark matter particles would be much more spread out. It's kind of intuitive that "heavy stuff sinks to the bottom," but it's a little more complicated because the dark matter particles don't bump into things very much--they don't interact and slow down in ways you're used to.