## 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.

## Monday, October 30, 2017

### Reconstructing history

There’s not a lot of written history about the area that is now Liberia before the American settlers came.

To know what happened, you have to piece together strands of evidence from widely separated records, and from traditions, language families, and genetic families across a fairly large area of Africa—and I am not in any position to do that myself.

I greeted the appearance of Between the Kola Forest and the Salty Sea with enthusiasm, and bought a copy. After reading the introduction, I'm starting to wonder. He seems to have his references to Ham a little mixed (may not be entirely his fault--references are inconsistent), doesn't seem to have a good handle on the history of slavery in Africa (all European and uniquely evil), UPDATED see full review conflates "blue-eyed Aryans" with all Europeans, and approvingly cites the "black Egyptian" claims. Sorry, I read Herodotus too, and can look at the pictures the Egyptians painted, and read some of their folk-tales—ancient Egyptians were not of sub-Saharan descent. Recent DNA studies bear out the obvious—modern Egyptians have more sub-Sarahan ancestry than ancient ones. That Nubia conquered the north a time or three I can believe--I'd be surprised if they didn't. That Nubians were the ancient Egyptians isn't possible.

If he can't get the well-documented stuff right, I wonder what admixture of imagination is going into the less-documented material? I shall continue—I expect to learn something—but I am less happy.

### Reference missing

There's a story about a faculty party at some university, during which the topic of Velikovsky came up. An astronomer said to the MidEast historian "His ideas about the planets are complete rubbish, but he makes interesting points about the Egyptian historical record." The historian replied that "That's funny—I thought his astronomical ideas were interesting, but his dynastic chronology was junk."

I paraphrase, and I think there were three involved. Does anybody know the original?

## Friday, October 27, 2017

### Anonymous calls

In the released Kennedy files there's a report about an anonymous phone call 25 minutes before the assassination. I begin to see one reason why so much was filed away for years.

The more notorious the crime, the more rubbish the investigators have to sort through.

Just for fun, how many explanations of that memo can you come up with in 10 seconds?

### Panic!

New Jersey Officials Warn About Marijuana Edibles Being Given Out As Halloween Candy Treats.

### Wikipedia

We all know (or I hope we do) that Wikipedia is very unreliable on any subject that involves politics or disputed social issues.

My experience with the science articles has been that they're not always very clear. The math sections, on the other hand, have been, on the whole very useful and complete. I often have to chase through a list of definitions, and I wish wish wish more mathematicians would use examples in their communications (they use plenty in their research!).

The Motherboard article on the subject is a bit over the top. OK, way over the top. I know plenty of practicing scientists, and I can't think of one who wants knowledge restricted to an elite, and on the contrary, quite a few who volunteer in gigs to explain things to youngsters.

The problem isn't that "you can imagine impenetrable writing as a defensive strategy wielded to scare off editor-meddlers." The problem is that the science writers a) don't have huge wads of time and b) don't really know their audiences. And c) want things to be accurate--the imprecision of everyday language can be terrible. (Think of all the different meanings of "energy" you find in popular language--from heat to personal vivacity to obscure mystical flow up through your lung when somebody pokes your foot with a needle.)

FWIW, years ago I proposed that our grad students be required to prepare a web "poster session" of their theses, with a target audience of high school seniors who have at least algebra and some physical science background. Somebody would have to create a network of web pages to explain the background, of course, which their thesis-pages would reference. Crickets

## Thursday, October 12, 2017

### Mine! Mine!

AVI illustrates an application of Acton's Law, with treatment beds.

### Excitement

This week is full of phone conferences. We issued a bulletin announcing a nice very high energy "track-like" event, and this events seems to coincide in direction and time with a gamma ray blazar.

It would be wonderful to be able to associate a neutrino with a known source (it turns out to be rather hard), and the presence of two kinds of messengers (neutrinos and gamma rays) would give hard evidence for some classes of models of what's going on there, and serious challenges to others.

Scuttlebutt holds that the recalculated direction doesn't point as cleanly at the blazar as the first estimates said, but we'll see--probably by the end of the week.

BTW, a muon neutrino produces a muon through a charged current interaction, and that muon track points back pretty well to where the muon neutrino came from. An electron neutrino produces an electron, and that showers very quickly--you get a dramatic amount of light but not much of a track to point with. A tau neutrino--we've apparently had some taus, but it has proved rather hard to distinguish them from the electrons. Some of the time the tau track should shower quickly like an electron, but sometimes we should get a "double bang:" an interaction and shower, followed by a short track and another shower--sort of like a dumb-bell. So far we've not seen the double bang.

### Speed limits

John Lower wants to redo our speed limits, based on measurements by smart sensors in traffic control systems. He thinks that might make a lot of speed limits slower.

Redoing the old studies from the 50's and 60's makes sense. Adjustable speed limits does not: keep the number of driving variables small if you want minimum confusion. For example, reversible lanes are OK if there are physical barriers that shift, but if they are controlled by overhead X or O symbols you are asking for accidents. "Motor memory" of how fast I am supposed to be going along street-type X plays a role in my driving style, and I suspect I'm not alone.

And if photographic speed limit enforcement starts to become ubiquitous, I expect a significant rise in vandalism. Air rifles and slingshots and paintball guns would probably be useful for the purpose.

UPDATE: "Unknown" points out in the comments that the variable speeds can work.

## Saturday, October 07, 2017

### Busted!

My flight was delayed into O'Hare. I suspect luggage is loaded in alphabetical order, and unloaded in reverse alphabetical order.

When I finally got my suitcase I got into the line for customs (*), and observed my first bust. I don't know if it was the same little beagle I've seen before or if they have a family of them. The dog had identified a suspect. The agent on the other end of the leash was confiscating ...

Bananas. This was a fruit-sniffing dog.

(*) I dutifully filled out the card on the plane, but you use kiosk questionnaires now and give the customs agent the receipt.

## Thursday, October 05, 2017

### Day 5

The weather forecast on accuweather.com predicted wind gusts of up to hurricane strength this afternoon. Looking at the trees in the protected courtyard, I can believe it. It's supposed to keep up for another 3 hours. I wonder what that will do to the double-decker buses? I'm supposed to take one (the 100 line) this evening to get to the dinner... UPDATE Buses are not running, neither is sBahn (trees across the tracks), and some uBahn are closed too.

Just for laughs I went by the Pergamon--long long lines that weren't moving. (Ditto for the others) I had other things to do anyway.

There are still a lot of bullet marks in the older buildings around here, and the train support. (I'm not sure what you call the brick and stone buildings the tracks are built on. At the stations these are filled with shops and food places.)

It is sub-50, damp with occasional rain, and quite windy. At least the weather should be OK for the flight out tomorrow. Staying put for now.

UPDATE: Xavier did a lot of damage. We walked to the banquet aside from one last O(60mph) gust it wasn't bad anymore, but branches were down everywhere and the hooded crows were angry as all getout. Monbijou Theater had boarded up their bar, but their signs and banners were gone and most stuff was knocked down. Even fence sections weighted with 200lb of concrete were knocked over. But the giant banners for the museum across the Spree were still there.

## Wednesday, October 04, 2017

### Day 4

Planning meetings today. My todo list expanded, with documentation rising higher on the list. That is to say, prying loose documentation about the data-files various groups created. If you want somebody to be able to replicate your study with more data, or even know whether your data-files are relevant to their work . . . please tell us what software you used, and what cuts are on the data.

This part of Berlin is a tourist area, with lots of people from all over--including lots of Germans visiting too. Lots of restaurants with tables outdoors--which would be much more enticing if it weren't 50 and gloomy with scattered showers. Now if I just had time to go see the Ishtar Gate...

Food may be good, but alone you are just eating: dining needs friends.

## Tuesday, October 03, 2017

### Day 3

German Unification Day. Most shops are closed, and there are more children about than there were yesterday.

I went hunting for a grocery store, but didn't recognize it at all--looked more like a bakery than a place to buy turnips. And it was closed.

A block away is the original Weber office, with a giant round grill out in front.

Lots of talks. More when I wake up.

The Neue Synagoge is just down the street from me. Yes, there's a chain, and yes, those are policemen. At night too.

## Monday, October 02, 2017

### Old story

Every weekday a man would walk to the news stand to buy a paper, and then stand at the bus stop reading it.

The vendor didn't like him, and wasn't shy about it.

One day another man waiting there too said "Excuse me, but you know there's another news stand across the street. You don't have to buy from that guy."

The man with the paper replied "I'm not letting that insulting SOB decide where I buy my newspapers."

Some people want everything to be political.

### Berlin Day 2

The hotel corner is a hub for several trams, and the sBahn is half a block away. The rooms face the courtyard, so the noise doesn't bother people--or at least doesn't bother me. On the other hand, the room we met in parallels the tracks, so every subway or commuter train distracts a bit.

My talk went well, the others were interesting, though I wonder about the Markov Chain Monte Carlo(*) approach to scattering. As one of the attendees pointed out, there is no theoretical reason why the approximation he was testing should work, and in the end you have to rely on "Well, the distributions look OK in this case"--and the only way to know that they "look ok in this case" is . . . to do the usual estimation, with all the CPU time expense that entails.

I forgot to mention one nice feature of the airport: when we got off the plane, the baggage pickup was right there. No heading down to a common pool of baggage carousels and scouting about for the right one--or what will be the right one when the current deposit is done. Security is probably much better, too.

The Grand Bar served up food very quickly, and with much nicer presentation and ambience than you expect from a "bar." If you eat equal volumes of broccoli and potatoes, they cancel out, right?

I was curious if the simple pre-pay cards would let me make calls from here to the US, but O2 says no. Oh well.

I've never seen Cabaret. I suppose I should, one of these days. There are plenty of posters and graffiti up condemning the AfD as nazis: I don't think nazis will make any kind of comeback in my lifetime, or my children's lifetimes. Not with that name anyway, whether chosen or imposed.

Tour boats on the Spree at night are lit up with bright lights, and they sometimes use searchlights on the clouds as well. Tried to take a picture, but the contrast was terrible. There's nothing like the dynamic range of the human eye.

(*) No, I'd never heard of it before, but Jakob said he and some others had brainstormed it for a while and concluded that it was semi-impossible. I really really want a Journal of Stuff That Doesn't Work.

## Sunday, October 01, 2017

### EMP

I wonder how seriously the powers-that-be are taking EMP risks.

We hear how EMP would fry computers, sensitive electronics, fancy auto ignition systems I wonder about how likely that is if you're not at ground 0, and mess up the power grid. Bye bye water supply, communications, etc.

Despite the CNN rant we were subjected to this morning(*) about Puerto Rico, you can't pre-position enough supplies with only a couple of day's notice, and when the storm takes out everything you can't wave a magic wand and have a hundred thousand generators instantly materialize. And figuring out what to do in what order isn't trivial.

If we wanted less exposure to EMP, how would we design things? The national power grid needs work; some robustness might be designed into it. (Please?!) Do we have ways to hack and slash local chunks back together again (chucking out all the smart power stuff, and maybe not even hanging power lines high in the air the first month)?

Lightning strikes cause bad transients--can we look at how to isolate buildings from them? That might carry over into EMP hardening too.

We're doing a lot of alternative energy stuff: there's no way that wind could replace coal, but the tie-ins that make wind's variable supply feed into the grid might be extended to pre-positioned backup generators.

We can't move as much stuff as efficiently without fast computer communication. Do we still have fall-back approaches?

Are backup generators standard for water towers?

(*) The admin spokesman didn't seem to understand the situation either.

### Disconnected notes from Berlin Day 1

Around the corner from the Monbijou Hotel is "Flakes and Shakes." They claim to have over 100 types of American breakfast cereal for sale. I didn't go in to see if Bruce Jenner is still on Wheaties.

Along Monbijoustrasse, on the other side of the Spree, is a block of vendor stands. At the end of the block is an elevated trash bin with the label "Museum of Contemporary Trash" likely a dig at Museum Island across the street.

The whole area is redolent of sewer: one of those little things that didn't get updated at reunion time. Hackescher Markt is what you'd get if you put high end boutique stores in mini-plazas made of old buildings and then glued them together. The layout is straightforward but that doesn't matter, you get turned around anyway.

Berlin is a graffiti city. Some is coarse and stupid, some is gang related, some political, but there seems to be a fair amount that relates to the art community. (I will give the benefit of the doubt for the word "art.")

When you look down a random street in this area you're apt to see a building or three older than a century, and street names and sometimes monuments for famous Germans. And tourists taking pictures of the same. Museum Island is here--lots of good art and significant reminders. I can imagine if I were a musical Berliner who wanted to make a name for myself and was faced daily with reminders that I'm not even remotely a new Beethoven, I'd be tempted to use novelty as a shortcut to innovation, or maybe just as a primal scream. "I can't paint like Durer or write like Goethe or study and think like Humboldt but I am a painter/writer/'thinker'!" OK, primal scream and thinking don't go very well together.

The Berlin Wall was graffiti-ed up as a protest--that would tend to make a big mental link to graffiti and liberty.

At any rate, it is a bit disconcerting to see an area painted up like a disputed territory in Chicago.

Restaurants all over the place too. I decided to try curry-wurst. Once is plenty--it tasted ok but I've still got a cannonball in my tum.

I'm trying to stay awake long enough to start the time shift. Gets dark earlier here than at home...

I got off at the wrong stop from the TXL bus, but still had time on the ticket so took the S42 loop on the sBahn (the S41 going the opposite direction is under construction--you've got to either take the bus or go the loonnnngg way around the loop) and asked a friendly native which direction I wanted to take. Trains often get names from the last stop, which may be off the map and is in tiny print anyway. Which direction you get depends on which platform you're on.

### Bridge technology

The compilation is available online in a scan of a copy--a few pages are not readable and many are hard on the eyes.

WHY BRIDGES ARE BUILT IN SECRET

L. Nelson (Legends of Liberia)

Long before white men were known in the land there lived a rich woman by the name of Sagba Massa. Sagba possessed a certain magic ring which she always wore on her hand; with this ring she could summon and control the power of spirits and forest devils, and her clan, whom she rules, prospered accordingly. Her lands yielded abundant crops, rain fell when rain was needed, and evil beings who walked in the night left her people alone.

The Chief of Sagba's tribe, a wise old man called Mana Kpaka, sent messages through the land requiring lesser chiefs and clan leaders to assemble at his town for a converence concerning tribal warfare. Sagba Massa set out on her journey to this town, and on the way she was obliged to cross the Yanjah River. While crossing in a canoe she saw a beautiful woman sitting on a rock, and wondered who she was. A moment later the woman disappeared, and Sagba, whose hand was trailing lightly in the water, suddently felt her magic ring drawn gently from her finger.

She cried out in alarm and peered down into the shining water, but saw nothing there. The beautiful woman who sat on the rock had been a water spirit, and doubtless it was she who had stolen the precious ring. Sagba made camp on the river bank and called up her best diviners to discover what she must do: the diviners read their sands and gave her their advice.

Three men were brought from distant places. One of them had power over water. The second had power over light and could see into the very heart of mountains. The third had power over earth, and could crush the biggest rocks to powder in his hands. Sagba Massa paid them well and commanded them to find her ring.

The first man tipped the river on its side.

The second man saw the ring hidden inside a rock which lay in the river bed.

The third man lifted the rock and broke it, and having found the ring he gave it back to Sagba. She went to the conference called by Mana Kpaka, and when returning she decided to build a bridge across the Yaajah river, a bridge which would nowhere touch the water.

With the aid of her ring a number of spirits were summoned and they were told to build a bridge from bank to bank in such a way that men who crossed might be beyond the reach of mischievous river spirits. The spirits said they would work by night, but men must work by day. Trusted men were called upon to build the bridge by day; and the spirits threw building medicine on them so they would build well and make no error. The spirits selected two large trees on opposite banks, and swung stout lines of cane and vines across the river from tree to tree; but they only worked by night, when no one was about. The men used secret knots and the cunning of their medicine to weave a slender footwalk between the hangling lines; they worked only by day, and no man who was not one of them was permitted to be there.

Thus the first suspension bridge was built, and now the manner of this work is a closely guarded secret handed on from father to son. The secret is known only to spirits and selected groups of men, and anyone who tries to watch is killed.

Strictly speaking this isn't an explanation of why the spirits wanted everything to be secret, but never mind that.

You would think that the people walking over it every day would be able to look at the knots and reverse engineer the method, but I'll bet there are some non-obvious tools involved. Think patent enforcement.

I couldn't figure it out, but I'm no good with visualizing, or successfully tying, any but the simplest knots.