Overshadowed

Overshadowed

What kind of college has its first day of classes on the same day as a total solar eclipse? I don’t think I’ll drive to Nebraska after all.

Look, I get that a total eclipse is a spectacular thing to see, but college or no college, this is Nebraska we’re talking about. (Yeah, or any of several other states, but not much of an improvement over NE, and the closer ones are more likely to be cloudy anyway.)

Besides which, all I have to do is stay alive and well and living in Syracuse another seven years, and guess what:

April 2024. In Syracuse (or, better, Rochester) it’ll be cloudy, pouring rain, and cold. Perfect.

 

Advertisements

Science of the Solar System

I just finished an online course on the science of the solar system, taught by Mike Brown (alias Plutokiller) of Cal Tech. It was pretty great! I learned a lot. Brown did an excellent job presenting it — as I couldn’t help but notice from the few guest lectures along the way; they weren’t bad, but I kept wishing they were as good as Brown’s. (Pro tip: Look at the camera, guys!)

I feel like I now know more (or perhaps I should say, am less ignorant) about Martian geology than terrestrial, which leads me to think maybe a geology course sometime.

Also, as an indirect result of taking this course, I now own a chondrite and an iron meteorite. No achondrites, no pallasites, yet.

 

A leisurely few days of aaaaaaaaaaaaarrrrrrrrgggggghhaaaaaaeeeiiiiiiieeee

Last summer somehow most of the things I wanted or needed to do didn’t conflict much. This year is being more difficult.

So the SoLID collaboration meeting ended up being Thursday and Friday, not Friday and Saturday, so that was good, but I still had to get back before the rest of the weekend’s activities. That plus cheaper tickets meant flying into and out of Norfolk, VA and driving from there to Newport News — during rush hour, both ways. I lived. I did speak at the meeting, briefly, about my simulation work on the PVDIS baffles.

Making my flight back required me to leave Jefferson Lab before things wrapped up Friday, but I didn’t miss much of significance to me. Waze told me to get off I-64 for several miles and back on just before the Hampton Roads Bridge Tunnel, which kept me out of the worst of the Interstate parking lot. The flights home, like those to Virginia, were amazingly non horrible and I got back around midnight.

The plan from there was: First Syracuse Rocket Club launch of 2015 Saturday morning, morris tour Saturday afternoon, 20 mile bike ride Sunday morning, and Heather’s commencement ceremony Sunday afternoon.

The forecast for Saturday didn’t look too great, too much mention of rain, but in fact, at least where I was, we got no more than a light five minute shower in the early afternoon. I got to the field around 9:00, helped set up, and got two, count ’em, two rockets in the air before it was time to boogie on out and head for downtown. At that I missed the first dance stand, but I met up with the Binghamton Men, Thornden, and the B. F. Harridans for beer and lunch at J. Ryan’s, followed by dancing at Hanover Square, beer and dancing at Mully’s, dancing at the Dinosaur Bar-B-Que, dancing at Perserverence Square, beer and dinner at Clark’s Ale House, and dessert at the Hosmers’ house.

It was pretty great.

Excellent weather today, and I went off to the first Cycle in the City bike ride of 2015. North to Onondaga Lake, south to Webster’s Pond, and east and west in between to various other bodies of water. 20 miles total. Then home, change, lunch, and off to the Civic Center for SUNY Upstate Medical University’s commencement exercises where Heather got her hood denoting an MPH degree. Kenny and I had dinner at Panda West before heading home.

 

Speed of sound, Or, No, it’s not freezing in here

Speed of sound, Or, No, it’s not freezing in here

I was thinking about my frequency measurements and how I kept getting best fit slopes corresponding to very low values of the speed of sound. I’d hypothesized this might have something to do with the mouthpieces I was using, and I found some possible corroboration in Arthur H. Benade’s book Horns, Strings, and Harmony: “To be sure, an enlarged mouthpiece cavity can lower the pitch of the vibrational modes, but they are lowered equally, except for the highest ones.” A little too vague to make it clear whether the effect looks like a lowered slope, though.

Edit: But yes, it has to. The enlarged cavity should matter less for a long tube than for a short one (since in the latter case it’s a relatively large deviation from a perfect cylinder, while in the former case it’s relatively small.) That means f will be lowered by more for a short tube than for a long one, or in other words the variation in f with L_{eff} will be less than expected; equivalently, the variation in L_{eff} with 1/f will be less than expected — that is, the slope will correspond to a lower speed of sound.

Then I realized these tubes are just about the same diameter (inside) as an earbud.

So I shoved an earbud in one end and listened to the other while using this site to play a calibrated variable frequency tone. I could indeed hear the resonances. I couldn’t pin down resonant frequencies with precision better than several hertz, I think, but using several tubes and tube combinations I got enough points for a reasonably accurate fit to a line. After discarding one blatant outlier (yeah, I could be more rigorous, but really, it was an outlier) I got a sound speed at around 19°C of 340.9 m/s — it should be about 342.7. sosMuch closer agreement. I also got an effective length for the “mouthpiece” of –3.5 mm. Negative? Sure, because the earbud was pushed into the tube. By more than 3.5 mm, of course, but I’m sure the error bars on that value are large enough to cover that.

Granted, I did this in the slightly warmer bedroom rather than the chillier basement, but there’s no way the low sound speeds I’d been getting were entirely temperature related. It’s not below freezing down there! So I think it really has to be a mouthpiece effect.

Universe Song, quantitatively evaluated

Universe Song, quantitatively evaluated

Something reminded me recently of the Universe Song from the 1983 Monty Python movie, The Meaning of Life. You’ve seen that clip, right?

It’s a funny song and a funny sketch. It also is, unlike certain science fiction TV shows, reasonably accurate with its facts and numbers. You quite literally could use nothing but your knowledge of this song to stand a good chance of passing an Astronomy 101 final exam. Shall we fact check?

… a planet that’s evolving
And revolving at nine hundred miles an hour,

Not only is Earth evolving — it’s still cooling, for one thing, and the continents are drifting around, and the magnetic field flips every once in a while — but it is rotating (“revolving” refers to its motion around the Sun, but I quibble), and while one usually uses angular velocity measures such as radians per second or hours per revolution or something, one certainly can observe that the Earth’s circumference at the Equator is 24,873.6 miles (source) and that relative to the fixed stars, Earth rotates once in 23.934 hours (same source). So the speed at which Earth’s surface moves at the equator is 1039 miles per hour. The song’s value is low by 13%. Not too shabby, though “a thousand miles an hour” would have scanned just as well and been more accurate.

That’s orbiting at nineteen miles a second, so it’s reckoned,

Likewise, Earth’s orbital circumference and sidereal revolution period are 584,019,311 miles and 365.26 days, for an orbital speed of 18.51 miles per second. Song is high by a mere 2.7%.

A sun that is the source of all our power.

Not quite true but close. Solar power comes from the Sun, of course; wind power comes from air circulation driven by the Sun (and Earth’s rotation); water power comes from water flowing downhill after solar evaporation lifted it up; fossil fuels come from ancient life that either photosynthesized using sunlight or fed on life that did. Nuclear and geothermal energy, though, does not have a solar origin. Not our Sun, anyway.

The sun and you and me and all the stars that we can see
Are moving at a million miles a day

The Solar System is about 28,000 light years from the center of the Milky Way, and it revolves around that center once in about 230 million years (source).  Doing the math, that comes out to 12.3 million miles per day.

But the song apparently isn’t referring to that speed, but the slower speed with which the Solar System is moving toward Lambda Herculis, in a reference frame in which the other stars are, on average, not moving: about 12 miles per second (source). In other units, that’s 1.0 million miles per day — exactly (to within stated accuracies) what the song says.

But the previous line’s wrong: that’s the Sun’s speed relative to the other stars, not the speed of “all the stars that we can see” relative to… something. Well, they’re moving a million miles a day relative to us, but that’s stretching the interpretation.

In an outer spiral arm, at forty thousand miles an hour,

I’d prefer to say “the outer part of a spiral arm”, but yes. And that’s just the same speed again in different units; 12 miles per second is 43,200 miles per hour. The song’s value is 7% lower.

Our galaxy itself contains a hundred billion stars.

That’s the right order of magnitude (source). I’ve seen 200 to 400 billion claimed (source). Large uncertainties here due to the number of dwarf stars which are hard to detect.

It’s a hundred thousand light years side to side.

Also about right (source).

It bulges in the middle, sixteen thousand light years thick,
But out by us, it’s just three thousand light years wide.

And also the right order of magnitude, with this source giving about 10,000 light years for the thickness of the central bulge and 1000 light years for the main disk. There’s considerable uncertainty in these numbers — the Milky Way is harder to view than many other galaxies, because we’re in it and dust obscures a lot of it.

We’re thirty thousand light years from galactic central point.
We go ’round every two hundred million years,

We’ve covered those numbers already, quoting 28,000 light years and 230 million years. So they’re correct to within about 15%.

And our galaxy is only one of millions of billions

Another number that’s hard to estimate, but one source quotes 100 to 200 billion galaxies in the observable universe. “Millions of billions” is a whopper of an overestimate… except that the observable universe is likely only a small fraction of everything there is, the size of which we have no way to estimate with any precision, and it may well be infinite, in which case this is a whopper of an underestimate.

The universe itself keeps on expanding and expanding

Well, yes.

As fast as it can go, at the speed of light, you know,

Well, no. Relative expansion velocities depend on distance and can be less or more than the speed of light. But the bounds of the observable Universe are governed by the speed of light: it’s the region in which light has had enough time to reach our eyes.

Twelve million miles a minute, and that’s the fastest speed there is.

It’s the fastest speed at which a particle or signal can propagate through space (according to present understanding); space itself, as I alluded to above, can expand faster. The speed of light in vacuum is defined to be exactly 299,792,458 m/s (source) (or in other words, the meter is defined to be 1/299,792,458 the distance light travels in a vacuum in a second). In other units, that’s 11,176,943.8 miles per minute. The song’s value is 7.4% too high. But “eleven million” wouldn’t have scanned.

And pray that there’s intelligent life somewhere up in space,
‘Cause there’s bugger all down here on Earth.

This is correct (source).

 

SoLID, Souderfest, and PAVI 14

A week and a half of physics meetings. A week ago Tuesday I flew to Newport News. Or tried to. Actually I flew to Norfolk after the flight to Charlotte from which I would  have flown to Newport News was delayed by weather. I ended up getting to Newport News earlier than planned, but only by having to drive on I-64 and go through the Hampton Roads Bridge-Tunnel.

Anyway, Wednesday and Thursday were the SoLID [SOlenoidal Large Intensity Device] Collaboration Meeting, our first since November and our last before the Director’s Review of the SoLID project. Friday I returned to Syracuse.

Sunday was Souderfest, a symposium in honor of Paul Souder’s 70th birthday, at the University, with a lot of good talks by the likes of Krishna Kumar, Emlyn Hughes, Charlie Prescott, Tim Gay, Mike Lubell, and others. Some of them were about experiments we did back 20 or 25 years ago and there were mentions of things I’ve hardly thought about in years. We concluded with dinner at the Skaneateles Country Club. Then I moved into room 310 at the Stella Maris retreat center in Skaneateles for the weeklong PAVI [PArity VIolation] 14 [as in 2014] conference. Among miscellaneous duties as a local, I was in charge of getting talks onto the conference computer and up on the screen, as well as up on the web site. So I was in fact present (physically anyway) for I’d say at least ~90% of each of 100% of the talks.

They weren’t as uniformly interesting to me as the Souderfest ones but mostly pretty good. Mainz A4 has an interesting new parity violating electron scattering (PVES) result at Q^2 = 0.6, more in line with the G0 experiment than HAPPEX III. There’s a report muonic 3He and 4He give nuclear radius results that agree with electron scattering measurements, in stark contrast with the puzzling situation for the proton. Nothing earthshaking on the theory side, I’d say; most interesting to me was conclusion that charge symmetry violation effects are negligible or at least small for PVES experiments coming up.

Monday Gordon Cates gave a public lecture on applications spun off from basic research, emphasizing his development of lung imaging technology based on polarized 3He. Tuesday there was a very nice concert by a quartet put together specifically for the conference, the Jefferson Quartet, which apparently intends to keep going afterward. Beethoven Op. 18 No. 4, Shostakovich 1st Quartet, and Mozart Clarinet Quintet.

Wednesday afternoon was spent on board a tour boat, down the lake and back. It was also our poster session. (Pier reviewed.) I went home that evening for Kenny’s 15th birthday.

Thursday night was the banquet, and I met our guest speaker, Congressperson Dan Maffei, pro-science and a member of the science committee in the House. Conference wrapped up Friday, I stayed in town into the evening, went to hear part of the Skaneateles Concert Band’s concert (I think I like LaFayette better) and then came home.

Yes, but it’s a dry cold

Yes, but it’s a dry cold

 

 

We have a great big plastic jar with pretzels in it, and I noticed every time I reached into it, my hand felt cooler. I figured it was ridiculous that the temperature inside the jar should be lower than outside, so why the cool feeling? Moving air makes you feel cooler but I didn’t think the pretzels would really be stirring up a breeze. The only other possibility, it seemed to me, was humidity: If the pretzels were absorbing water from the air, then the humidity of the air would be low, and that would promote evaporation from the skin which would make my hand feel cool.

So I stuck an electronic thermometer / hygrometer in the jar and waited. Care to guess what the humidity reading leveled out at?

2014-06-24 17.34.43

“- -%”, which is this device’s way of saying “zero”. Outside the jar at the time, it was about 55%. Yep, it’s dry in there!

It’s the same principle behind the idea of throwing your phone into a bag of rice if it gets wet. Rice dries out air, dry air dries out phone. If you don’t have rice, pretzels would probably work too.

 

The ninety percent

Yesterday my wife and I were talking and the subject of faster than light neutrinos came up. “Someone did something wrong,” I said, “either the experimentalists or the theorists.” Then I added, half jokingly (if that) “Probably a bad cable. Ninety percent of experimental physics is finding the bad cable.”

Today’s news: It may have been a bad cable.

Well, okay, a bad connection to a cable. Messing up the GPS timing and making the neutrinos look too fast.

Well, I’m surprised I predicted it a day ago, but I’m not surprised by the news itself. Ninety percent is an exaggeration, sure, but it’s true a large fraction of all the problems you run into turn out to be something like cables or connections.

Understand, this is not really the physics equivalent of the tech support question, “Are you sure the monitor is plugged in?” Even a (relatively) small and simple particle physics experiment can easily use hundreds of cables in its data acquisition system. Big and complex ones… you don’t want to know. Here’s a photo from Brookhaven to show you what I mean:

If any one of those cables is bad, or a connection is bad, or a cable is plugged into the wrong place, it may mess up the results in ways that can drive you nuts trying to figure it out. (Or it may not; a few percent of those cables probably are actually obsolete and don’t do anything.)

As the story linked above mentions, there’s another problem they’ve found that could be making the neutrinos look too slow. They won’t know for sure what effect either problem had until they do more tests after they’ve fixed them. But I’m guessing the neutrinos will be obeying the speed limit next time they measure them.

 

Bigger than Jesus, Jesus?

Gizmodo does some ludicrously bad science reporting, but they outdo themselves in Jesus Diaz’s story about the rumors regarding the upcoming LHC announcement:

this will be the biggest news in the history of physics since the birth of the Theory of Relativity

Sheesh. Even by Internet standards of overhype this is way off base. If the rumors are true then what we’ll be told is: We’ve found some evidence that a particle most of us expected to find is there.

Whoopee.

The discovery of neutrino oscillations (which proved neutrinos are not massless) was as big if not bigger. So was the discovery of the weak force carriers, the W and Z particles. So was the discovery of weak neutral currents. Of proton substructure — that is, quarks. Of parity violation, and CP violation. Of antimatter. Of nuclear fission and fusion. And a dozen other discoveries that either upset the then prevailing theories, or confirmed theories that until then were still regarded as interesting but speculative. And that’s just in experimental nuclear and particle physics. On the theoretical side: Quantum mechanics, quantum field theory, the quark model, gauge theories of the weak and strong interactions, electroweak unification… and more. And then there have been big developments in other fields of physics too, many of which were at least as significant as a Higgs discovery. (High temperature superconductors? Dark matter and dark energy? Lasers?)

In addition to which, if the rumors are correct, we won’t even be getting a discovery. We’ll get some suggestive evidence, but far short of the statistical significance needed to claim a definite find.

So keep your pants on. If they’re starting to see a bump in the data, hey, great, but it’s not going to revolutionize anything.