Calvin’s parents forget to pay the gravity bill.
Category Archives: Physics
Even More Advice for the Physicslorn
After More Advice for the Physicslorn
Sure, if your neighbor claims he was abducted by aliens, and spent some time on Alpha Centauri learning the mysteries of that highly advanced civilization, it’s easy to conclude that maybe it’s time he upped his meds. But in an era when modern theoretical physicists are routinely batting around notions like extra dimensions, dark matter, dark energy, and parallel universes, the line between bona fide breakthrough and nonsensical physics-babble isn’t so clear. To the average person, saying the world is made up of tiny styrofoam balls only seems slightly crazier than saying everything in the universe boils down to tiny vibrating strings.
Includes a link to The Alternative-Science Respectability Checklist but not to Crackpot Bingo (until you get to the comments)
I suspect this goes over the head of the target audience without so much as a hair out of place. Or they’ve got their phasers set on “ignore.”
Photons Think
Because we can get them to concentrate. MIT opens new ‘window’ on solar energy
“Light is collected over a large area [like a window] and gathered, or concentrated, at the edges,” explains Marc A. Baldo, leader of the work and the Esther and Harold E. Edgerton Career Development Associate Professor of Electrical Engineering.
As a result, rather than covering a roof with expensive solar cells (the semiconductor devices that transform sunlight into electricity), the cells only need to be around the edges of a flat glass panel. In addition, the focused light increases the electrical power obtained from each solar cell “by a factor of over 40,” Baldo says.
The factor of 40 is in reference to the light collection, not solar cells themselves, i.e. you are collecting 40 times as much light as you’d get from the area of the edge of the sheet — there’s no comparison to what you’d get if the whole sheet were a solar cell. The action of the collector is much like my clipboard, except the dye is on the surface rather than inside the material. The advantages here would be in reducing the area of the solar cells needed, which are presumably much more expensive, and that some light would still be usable on the other side of the collector.
Fields, Fields, Everywhere
And Now For Something Slightly Different
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.
“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.
What's Opera, Doc?
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)
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?
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.
Can You Spare a Second?
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 0sThe 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.
Did I Read That Right?
This is the kind of post I start reading, and I begin to furrow my eyebrows as phrases and sentences pop up that don’t seem right or are obviously wrong. I though it was just bad science journalism, but realized it’s a rant-y agenda piece, with the supposed “science” reporting as a setup.
Superfluids, BECs and Bosenovas: The Ultimate Experiment
It starts off OK, giving some history, but then there was
Bosons are force carriers like photons of light and fermions are the matter we can touch.
Force carriers are bosons, but not all bosons are force carriers (universal affirmatives can only be partially converted, quoth the logician) — you can construct bosonic systems from an even number of fermions. Bosons have integral spin angular momentum, and fermions have half-integral spin, and the statistics that describe their behavior is different. An attempt to bridge the gap between science and a lay explanation that fails because it’s scientifically incorrect.
[helium is] produced by nuclear decay, as from radium and polonium, dangerous alpha radiation releasing, in fact bare nuclei of helium that eventually pick up electrons and form stable helium isotopes.
Here’s a journalistic archaeologism (it’s certainly not neo-) dangerous radiation. Nuclear radiation in invariably dangerous. Actually alpha radiation is pretty much harmless as an external dose, as it deposits its energy in a very short distance, so it doesn’t tend to penetrate even a layer of dead skin. The source is dangerous when ingested or inhaled. But the Helium nucleus is already stable (it doesn’t decay) even before it picks up the electrons — that makes it electrically neutral, not stable.
Wear This Ribbon if You Support (Bad) Astronomy
But if you can, since it’s 60 LY across, don’t ask me if your butt looks big.
[A] ribbon of gas, compressed and glowing due to a shock wave that slammed into it. The shock came from Supernova 1006, a star that detonated 7000 light years away from us. This was not a massive star that exploded, but a low-mass white dwarf, the dense core left over when a star like the Sun runs out of fuel. Still, the forces are roughly the same, with a titanic explosion ripping the star apart and creating eerie, unearthly beauty even in death.