Just Don't Make It So They Blow

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Sucky Schools – How To Repair Our Education System

Lots of good stuff.

Our schools are fact-junkies. We teach students thousands of useless facts that will be forgotten as soon as the next exam is over. Hell, usually they’re forgotten even before that, and then you see students cramming late into night, only to forget it all within 48 hours. How’s that for effective use of everyone’s time.
[…]
Standardized testing is like a black hole that sucks up and annihilates any learning it gets close to. It bends the very fabric of curriculum and students’ time.

via sciencegeekgirl

Hail to Thee, Blithe Neutron!

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TS2 on Target – view from the LOQ cabin

A brief overview of some neutron history

Since it carries no charge, one could not “weigh” a neutron directly in a mass spectrometer, but had to estimate its mass from the difference between deuterium and hydrogen. However in 1935, more accurate measurements allowed Chadwick to derive a neutron mass of between 1.0084 and 1.0090 units; the modern estimate lies almost exactly in the middle of this range, and so the neutron is appreciably heavier than the proton. Was Uncle Albert wrong? Chadwick immediately suggested (following Einstein again) that neutrons should have an excess of energy and be beta radioactive in common with other nuclei under like circumstances. It was not so easy, however, to verify this experimentally. But, partly owing to World War II, it was not until 1948 that neutron decay was verified – indeed, 12 minutes after they’ve been kicked out of the nucleus half of them will have split apart as Chadwick had suggested. So if you want to use neutrons, you can’t keep ’em in a bucket.

That last bit is a tad misleading — it’s no doubt referring to the decay, not the ability to confine. Since neutrons have a magnetic moment, they can be trapped. It’s a weird, shallow bucket, and it leaks, but you can keep ’em there until they decay.

It's Not an Inalienable Right!

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Jennifer’s enumeration of the PARTICLE BILL OF RIGHTS reminds me of a neat effect. I hope the second amendment

The right of unstable Particles to decay shall not be infringed.

only applies to militias fundamental particles, because people have been messing with that “right” for a while in atoms. These are demonstrated by some fascinating experiments in cavity QED I read about while I was in grad school. Probably the most familiar cavity QED phenomenon is the Casimir force, which arises from modifying the electromagnetic modes that are allowed to exist. In free space, waves of any and all frequencies and polarizations can exist, but when conducting surfaces are present, these alter the boundary conditions. Two flat conductors, closely spaced, will exclude many mode of electromagnetic oscillation, and because each mode carries 1/2 hf of energy even when there are no photons in that mode, this exclusion gives rise to the attractive force.

But there’s more fun to be had with this.

Imagine placing an atom inside a cavity under circumstances similar to where the Casimir force could be observed. You can prepare the atom in a state so that it can only decay by one mode — one transition, with a particular polarization of photon (either linear or circular), and you can also orient the atom so that the photon’s direction of emission (perpendicular pr parallel to the surface) will correspond to a photon mode that isn’t supported by the cavity configuration. When you do this, what is an atom to do? There is no vacuum fluctuation to induce it to decay, nor would a photon from that decay be able to exist. The atom is forced to sit there, grudgingly (or perhaps happily, I don’t think anyone’s asked) not decaying.

You can also choose your system so that there is a higher mode density, and get atoms to decay more quickly than they would in free space. (You can also repeatedly measure an atom’s state and keep it from decaying, in a phenomenon called the quantum Zeno effect, but I’m not going to go there. Or even halfway there)

So I must conclude that since this action is routinely taken on atoms and molecules, without writ or warrant, and we have declared that we do not torture inhibit decay, that this right does not apply to composite systems.

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Some references
Heinzen, et.al, Phys Rev Lett. 58 1320 (1987)
Jhe, et. al, Phys Rev. Lett. 58, 666 (1987)
Haroche and Kleppner, Physics Today Jan 1989 24-30

Hint: It's Not a Verb

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Sat-nav for flappers

Sat-Nav wristwatches have been around since 1920.

OK, the idea of a small chart scrolling on one’s wrist is clever, but the “sat” part of “sat-nav” stands for satellite, as in artificial satellite. What artificial satellites are involved here?

Yes, I have a peeve about using acronyms and abbreviations where one obviously doesn’t know what the terms stand for. Like saying “Please RSVP,” “LCD display,” “ATM machine” or “PIN number,” though these are examples of pleonasms rather than the first example, which is merely incorrect. But I digress …

Original article has several pictures of interesting inventions.

In Case You're Homesick for the Keystone State

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Last week I was vacationing in Bills’ country — it’s tough being a Dolphins fan these days, but especially so within an hour or so of Buffalo — getting my fix of hot wings (not hard to find pretty much anywhere these days) and Beef on ‘Weck (still a local phenomenon), which required me to travel through Pennsylvania.

Eleven freaking “work areas” on the way up. Similar on the way back, with some changes to the route, though I didn’t bother to count. Not one of them was “active” and no workers to be seen, though to be fair it was on the weekend, but I’ve seen this during the week on other trips. Ugh. Is “Under Construction” the new state motto?

Anyway, if anyone in the DC area is lonely for this, the stretch of Rt 50 just east of Glebe Rd. in northern Virginia has been a work area since early July, and Friday is just the second day I’ve seen workers there.