Monthly Archives: July 2008

And Now For Something Slightly Different

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The previous MOT video showed the atoms squirting out of the side when the trapping field was turned off. In this video things are more balanced, and you can see the atoms remaining in the beam overlap region, and fluorescing quite brightly. The trap is cycled on and off and you can see the trap “grab” the atoms and pull them back to the center; when the trapping field is left off it takes several seconds for the cloud to dim as atoms diffuse out, and that’s a qualitative sign that the atoms in the molasses are pretty cold. Probably tens of microKelvin.

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“Mr. Hands” is pointing out the trap axis at the beginning, as a cue to the person adjusting the trimming magnetic field. This kind of adjustment can be very laborious, as there are several parameters which need to be optimized, and they aren’t independent of each other. Beam alignment, magnetic field and beam intensity all need to be optimized, but all exert forces which can be offset by one of the the parameters, e.g. a slight imbalance in intensity can be offset by a small magnetic field, and the small amount of swirling of the atoms when the trap is turned off is likely an indication that this is the case.

However, at this level of adjustment, the atoms are the best indicators. An optical power meter or a magnetic field probe aren’t going to yield the precision necessary — they can only get you close. At this point you just have to wander around phase space, checking that you aren’t merely at a locally optimum signal. The true test comes when you can actually measure the temperature of the atoms, by imaging them in time-of-flight and seeing how much the cloud has expanded.

Seftonomics

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Via Kottke, The Economic Organisation of a P.O.W. Camp

Stories circulated of a padre who started off round the camp with a tin of cheese and five cigarettes and returned to his bed with a complete parcel in addition to his original cheese and cigarettes; the market was not yet perfect. Within a week or two, as the volume of trade grew, rough scales of exchange values came into existence. Sikhs, who had at first exchanged tinned beef for practically any other foodstuff, began to insist on jam and margarine. It was realized that a tin of jam was worth 1/2 lb. of margarine plus something else; that a cigarette issue was worth several chocolates issues, and a tin of diced carrots was worth practically nothing.

In this camp we did not visit other bungalows very much and prices varied from place to place; hence the germ of truth in the story of the itinerant priest. By the end of a month, when we reached our permanent camp, there was a lively trade in all commodities and their relative values were well known, and expressed not in terms of one another – one didn’t quote bully in terms of sugar – but in terms of cigarettes. The cigarette became the standard of value. In the permanent camp people started by wandering through the bungalows calling their offers – “cheese for seven” (cigarettes) – and the hours after parcel issue were Bedlam. The inconveniences of this system soon led to its replacement by an Exchange and Mart notice board in every bungalow, where under the headings “name,” “room number,” “wanted” and “offered” sales and wants were advertised. When a deal went through, it was crossed off the board. The public and semipermanent records of transactions led to cigarette prices being well known and thus tending to equality throughout the camp, although there were always opportunities for an astute trader to make a profit from arbitrage. With this development everyone, including non-smokers, was willing to sell for cigarettes, using them to buy at another time and place. Cigarettes became the normal currency, though, of course, barter was never extinguished.

Fifth Law, Redux

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Survival of the Sudsiest, or George Will happens upon the fifth law of thermodynamics.

“The search for unpolluted drinking water is as old as civilization itself. As soon as there were mass human settlements, waterborne diseases like dysentery became a crucial population bottleneck. For much of human history, the solution to this chronic public-health issue was not purifying the water supply. The solution was to drink alcohol.”

Often the most pure fluid available was alcohol — in beer and, later, wine — which has antibacterial properties. Sure, alcohol has its hazards, but as Johnson breezily observes, “Dying of cirrhosis of the liver in your forties was better than dying of dysentery in your twenties.” Besides, alcohol, although it is a poison, and an addictive one, became, especially in beer, a driver of a species-strengthening selection process.

This fits right in with concepts from Jared Diamond’s Guns, Germs and Steel, in that civilization which didn’t develop the kind of population densities (i.e. towns) compelling people to drink alcohol did not see the genes for alcohol tolerance selected for (along with diseases that mutated and jumped from domesticated animals to humans in these regions with high densities)

Random Nonphysics Post

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Extraordinary Tongues and the Animals That Use Them

The tube-lipped nectar bat from Ecquador has a tongue one and a half times its own body length. It shoots it out with amazing accuracy while feeding at night. This huge tongue (in proportion to the 5.5cm bat) is not stored in the mouth. It is attached to the back of the mouth but stored inside the rib cage. The bat in the picture is drinking a sweet drink left outside to attract it.

All of the sudden I feel the need to call someone a tube-lipped nectar bat.
Next time someone mooches off of me . . .

What's Opera, Doc?

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Kill the wabbit goblet, kill the goblet!

Splendid Oscillation
Learn how to destroy expensive glassware with the power of sound

Cool video showing a resonantly-driven crystal goblet, with a strobe slightly off-resonance. Then it breaks. And in slo-mo (though not super slo-mo, which would be extra cool)

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Notice the beautiful large wobbling standing waves in the video. The points in the glass which are oscillating the most are called the antinodes of the standing waves — where constructive interference is at a maximum. The locations that seem to be stationary are called nodes. They are experiencing continuous destructive interference. To shatter the glass, just turn up the volume until the amplitude of vibration exceeds the tensile strength of the glass. Most people don’t have the lung power to do this, so if you really want to break some crockery, either use an amplifier or hire an opera singer.

Units, Units, Who's Got the Units?

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Via Symmetry Breaking, I discover the link to Sensible Units, which uses a unique definition of sensible. Type in a distance, and you might get the equivalent in AA batteries end-to-end or Alaskan moose antler spans. Or find a weight in equivalent average housecats.

Then there is the List of unusual units of measurement

It in includes the Sagan, which I used not long a ago, unaware it had already been codified in Wikipedia. There are more mainstream units, such as the barn and the shake.

And then we have the List of humorous units of measurement, including the Smoot mention in the Symmetry Breaking post, and the Helen, a unit of beauty (a milliHelen being the beauty needed to launch a single ship).

Negative values have also been observed—these, of course, are measured by the number of ships sunk or the number of clocks stopped. An alternative interpretation of 1 negative Helen is the amount of negative beauty (i.e. ugliness) that can launch one thousand ships the other way.

I question a few of these. I would think that happiness would be measured in clams rather than puppies, because of the need to quantify not only the warmness and dryness (wet dogs bring forth little happiness) but the calibrations for breed of the dog. I can see arguments breaking out, because a standard Lab generates more happiness than a Schnauzer — lots more — according to my research.

And speaking of dogs, the unit for illness is missing, and how sick you are would be measured in dogs. Health, or rather fitness, would be in fiddles. Insanity (madness) would be in Hatters. Nervousness would be in rocking chairs, calibrated with a standard long-tailed cat in a standard room. Smoothness would have the units of silk. Stubbornness measured in mules, while gentleness is measured in lambs. Uselessness, which surprisingly is quantized, in tits on some standard bull.

I think there are some standards labs that need to get cracking. At 0.6 greased lightnings, if not faster.

Verus scientia

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How to identify real science, the better to filter out antiscience.

What is REAL science?

REAL science…
Recognizes its limits – Science only works with phenomena that can be independently verified by observations or empirical tests. This is a practical approach to the study of the natural world that has proven to be extremely conducive to the advancement of scientific knowledge. Since this approach does not rule out the existence of non-verifiable phenomena, any claims about the existence or non-existence of such phenomena are not scientific.

That’s R. E, A and L are at the link.

Can You Spare a Second?

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Why, yes, I can. I just happened to find an extra one floating around here.

The International Earth Orientation and Reference Systems Service (IERS) has announced a leap second.

A positive leap second will be introduced at the end of December 2008.
The sequence of dates of the UTC second markers will be:

2008 December 31, 23h 59m 59s
2008 December 31, 23h 59m 60s
2009 January 1, 0h 0m 0s

The difference between UTC and the International Atomic Time TAI is:

from 2006 January 1, 0h UTC, to 2009 January 1 0h UTC : UTC-TAI = – 33s
from 2009 January 1, 0h UTC, until further notice : UTC-TAI = – 34s

The proud parents had previously stated they didn’t care whether the leap second were added or removed, just that it had all of its fingers and toes.

Finger on the Button

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Kill Switches and Remote Control at Schneier.

Don’t be fooled by the scare stories of wireless devices on airplanes and in hospitals, or visions of a world where no one is yammering loudly on their cellphones in posh restaurants. This is really about media companies wanting to exert their control further over your electronics. They not only want to prevent you from surreptitiously recording movies and concerts, they want your new television to enforce good “manners” on your computer, and not allow it to record any programs. They want your iPod to politely refuse to copy music to a computer other than your own. They want to enforce their legislated definition of manners: to control what you do and when you do it, and to charge you repeatedly for the privilege whenever possible.
“Digital Manners Policies” is a marketing term. Let’s call this what it really is: Selective Device Jamming. It’s not polite, it’s dangerous. It won’t make anyone more secure — or more polite.