Monthly Archives: March 2008

Meeting, March

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The Quantum Pontiff has a brief summary of the APS March meeting, and notes that

There are a lot of physicists. Even if you don’t count the particle and nuclear and gravitational physicist who have their own meeting. Oh, and they are easily identifiable walking down the street in New Orleans.

Perhaps we are, but there are even more of us, because the Division of Atomic, Molecular and Optical Physicists meets in May. (The Canadian version omits the Optical, so you have DAMP physicists up there. Tee hee.) Though it seems some of them showed in in N’awlins, from other summaries at nanoscale views where some cold-atom physics in optical lattices is mentioned. (third summary here)

Trivia Time, part II

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In Einstein’s 1905 paper in which he describes special relativity (“On the Electrodynamics of Moving Bodies”), there is a mention of what would happen to a clock on the equator vs. a clock at one of the poles. The clock at the equator is moving, and so should run slower. It turns out this is wrong, and I was surprised to find that there is some discussion, especially involving those who are convinced relativity is wrong anyway, about how this could be. (OK, not really surprised, considering that crowd) It would be correct if the earth were a rigid sphere, but it’s not — the earth is oblate because it is rotating. And surely, the arguments go, Einstein was aware of this. Well, it doesn’t really matter (and don’t call me Shirley). The reason has to do with general relativity, and in 1905, Einstein hadn’t yet formulated the theory!

The earth’s geoid (basically, the surface at sea level, without disruptions like currents and tides) is an equipotential surface. The gravitational potential (gh) and the kinetic potential (1/2 v^2/c^2) are exactly the terms that go into the dilation calculations, and if you spin up a deformable planet, you will get an exact balance between the change in gravitational potential with the kinetic potential. The dilation terms have opposite signs, and cancel. So clocks anywhere on the geoid always tick at the same basic rate — no correction for your latitude is necessary, though the elevation above the geoid must still be taken into account.

The Quote "Controversy"

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“Smart” quotes, “dumb” quotes. Nobody has explained to me why I should care, or why one is correct and the other incorrect. I think some people are caring about this a little too much.

(At the moment, I can apparently post only if I don’t use any html markups. Blogging in the dark ages. Cut-and-paste the link, if you care to.)

(problem fixed)

Belief, Knowledge, Faith

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ZapperZ’s post and subsequent link recalls a great essay that was in Physics Today a while back, and is available for viewing. Belief and knowledge—a plea about language

A few words in elementary physics— force, work, momentum, and energy—have carefully defined physics meanings. Their much broader everyday usage causes students a great deal of confusion until they learn the precise physics concepts. Rather than belabor such cases, I will focus on some words that are, I think, the root of considerable public misunderstanding of science: belief, hypothesis, theory, and knowledge.

[…]

We need our listeners to know what is tentative and what is not so that they understand better the ragged but cumulative progression of science and can use current knowledge effectively, with an understanding of its inherent uncertainties, in personal and political decision making.

New Data

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Unlike some pursuits, in science new information sometimes means having to revise your conclusion. Just after snarking about how unscientific congress is, I read that Bill Foster, another physicist, has been elected to fill Dennis Hastert’s seat.

So the raising operator has been applied by the good people of the 14th district in Illinois, at least until November, when the measurement gets redone.

Prof. Higgins Sings

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Why Can’t a Woman Be More Like a Man?

An interesting article on the gender-representation issue in the sciences. Many assume it’s all sexism, but whenever somebody checks to see if that’s really the case, two things seem to happen: they come to the conclusion, “Not so much,” and they are often attacked for raising the question. Congress has gotten into the act, with a push for a “Title IX for Science.” I’m all for removing barriers that might prevent women from pursuing a career in a science discipline, or shunt them into some other discipline against their desire, but if you don’t ask the question of how we know it’s sexism, such a path is, well, unscientific. (of course, that’s not surprising, since politics and political-correctness is involved). But the Title IX analogy fails, because science doesn’t have a men’s league and women’s league.

There is another essential difference between sports and science: in science, men and women play on the same teams. Very few women can compete on equal terms with men in lacrosse, wrestling, or basketball; by contrast, there are many brilliant women in the top ranks of every field of science and technology, and no one doubts their ability to compete on equal terms.

I think one of the problems in this issue is that some people are taking “men and women are equal” and subtly (or not-so-subtly) taking that to mean “men and women are identical.” And assuming that because the former is true that the latter must be as well.

via Twisted One 151

There’s also a new book, reviewed at the NY TImes, related to this topic. The Sexual Paradox by Susan Pinker.

Pinker parks herself firmly among “difference” feminists. Women’s brains aren’t inferior, she argues, but they vary considerably from men’s, and this is the primary explanation for the workplace gender divide

A Very Gravia Situation

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While poking around looking into the DST-doesn’t-save-energy story, looking for something that didn’t just link back to the WSJ story, I ran across this: a new lamp being hyped by some sites with a “green” tint, called Gravia. (a second story is here at treehugger)

The lamp took second place in the Greener Gadgets Design Competition. It’s described as being gravity-powered, which is wrong. It’s human-powered — you lift 50 lbs, and the weight falling back down supplies energy to some LEDs, and is supposed to supply 600-800 lumens, or the equivalent of about a 40-W light bulb, for four hours. Something about this immediately struck me as being wrong. You aren’t going to power the equivalent of a 40-W light bulb with that, not even with really efficient LEDs. 50 lbs, lifted a bit over a meter, will require 250 Joules of work. Over 4 hours, that’s 17 milliWatts of output. That didn’t add up — even the best LEDs are only 5 to 10 times more efficient than incandescent bulbs. There’s no way this can work.

And sure enough, that’s what I found

Continue reading →

Forward, Sproing!

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Spring forward tomorrow (or tonight just before bed). Daylight Saving Time begins in the US.

Three things:

– It’s saving, not savings.

– “Don’t blame me, blame the dee-oh-tee.” DST is the purview of the Department of Transportation. Universal time is unchanged — from a timekeeping standpoint this is a non-event. Displays get changed for devices that read out in local time, but atomic clocks that have displays read out in UTC.

– It apparently doesn’t save energy, at least in Indiana. But the story (not surprisingly) gets it wrong.

For decades, conventional wisdom has held that daylight-saving time, which begins March 9, reduces energy use. But a unique situation in Indiana provides evidence challenging that view: Springing forward may actually waste energy.

But later,

They conclude that the reduced cost of lighting in afternoons during daylight-saving time is more than offset by the higher air-conditioning costs on hot afternoons and increased heating costs on cool mornings.

So the decades-old “conventional wisdom” is only wrong if there has been widespread use of air conditioning during that time. If, however, the use of air conditioning has increased in that time, the conclusion is wrong. What you can conclude is that that right now, in Indiana, DST uses extra energy. Because they are selfish bastards who like air conditioners way too much.