More video that doesn’t have George C. Scott saying, “My Groin!” The Science Of Ball To Groin at glumbert. (Some annoying ads — and nothing else — tend to pop up on the video) This time, tennis balls (the projectile, not the target), while last time it was a baseball, but with a cup. Very different goals (though the same target), very different results.
Monthly Archives: May 2008
Toys in the Office: Special Blasphemy Unit
It’s a hand-held catapult-like device to chuck things, and yes, those projectiles are small nun figurines. So, it’s a NUN-CHUCK, just like it says.
I don’t show this off to just anyone at the office; I wait until I know them and use my judgement. But this is the internet. Caveat emptor.
I really should round out my collection and become an equal-opportunity offender, so if anyone has a line on a protestant-o-pult, or an atheist arbalest (arbalatheist?) or even a Buddhistic ballista, let me know. I got the above at American Science & Surplus, though they’re also available at Archie McPhee (and perhaps elsewhere)
The Long and Winding Coil
One project over the last several weeks has been winding coils for the atomic fountains. There are two different requirements, one is the so-called “C-field” coils and the second is the MOT (magneto-optic trap) coil pair.
The “C-field” is the bias field in an atomic clock that essentially tells the atoms which way is up, i.e. it defines the quantization axis. It also shifts the frequency of the transition, so in a frequency standard you need to know what the field is. In a clock (there is a subtle difference) you care about the stability, i.e. you don’t want it to change, so it’s enough to feed this with a precision current source to give a bias field of a milligauss or so. Two layers, up and back, so the pitch on each layer should tend to cancel and leave you with a vertical field, and about 600 turns per layer. There are also extra shim windings at each end to better simulate an infinite solenoid — a real solenoid’s field drops off at the ends, so we boost it back up a little. The drift region, where the atoms oscillate between the two hyperfine states (the “tick” of an atomic clock), sees a very stable field.
Pretty easy, but time-consuming (as it were); the basic winding took more than four hours. What you see is the jig I used, which has a stepper motor and a home-built feed system that wets the wire with alcohol to activate the bonding material. Square wire is used so it doesn’t have any gaps.
How Does That Work, Again?
I just read that the Chicago Bulls won the NBA draft lottery, meaning that the team with the worst record did not gain the first overall pick in the draft. Color me shocked. It was termed a “surprise” in some stories. Maybe it was a surprise that they won it, but not that the Heat — who, with the worst record had a 25% chance of winning the lottery —didn’t. Before the 1994 draft, the weighting was adjusted to give the team with the worst record a 25% of drafting first. Since that time, the team with a 25% probability has won exactly once: the Orlando Magic in the 2004 draft. (The Cavs in 2003 had a 22.5% chance, by virtue of being tied with Denver for the worst record.)
Whoever ends up in the cellar this year had better be praying for some regression to the mean.
Please Pass the Lamb Dip
Zapperz, back from vacation, notes that Willis Lamb passed away recently. The Lamb shift, the energy splitting of the 2s and 2p states of the hydrogen atom, was a huge confirmation of quantum electrodynamics and garnered him the Nobel prize, and you can read more about that here. But that’s not the only effect named after him. Another artifact is the Lamb dip.
The Lamb dip is not a sauce, nor is it related to sheep dip. It arises in a certain geometry of spectroscopy: if you pass a near-resonant laser through an atomic vapor, some of the light will be absorbed. If the laser’s frequency is scanned, you will map out an absorption profile of the atoms, but because they are moving, the absorption depends not only on the transition frequency, but also on the motion of the atoms, which causes a Doppler shift. So your absorption profile is really a representation of the thermal motion of the atoms. At any one frequency the light will be absorbed by those atoms whose motion places them in resonance with the light.
Coyote Goes a-Shopping
As fate would have it, Knopfler’s “Coyote” came up on the commute playlist this afternoon. But ACME supplied all of the Looney Tunes characters with products.
The Illustrated Catalog Of ACME Products
via nanoscale views
Grade Welfare
Some schools would really make Ralph Wiggum failing English unpossible.
Minimum-50 grading scheme reported at USA Today
Any grade below 50 is recorded as a 50. And this idea is not brand spankin’ new.
Their argument: Other letter grades — A, B, C and D — are broken down in increments of 10 from 60 to 100, but there is a 59-point spread between D and F, a gap that can often make it mathematically impossible for some failing students to ever catch up.
And so moving the finish line is the answer? Are these people daft? In a course with four exams counting equally toward the final grade, an unmotivated but smart student could ace one exam and then just not show up and still pass the course. This is symptomatic of never wanting to fail anyone for any reason, because it looks bad. Similar to my recent rant, here is another example of redefining “success.” Here, success is now having all the students pass, or minimizing the number of failing students, instead of maximizing the number of students learning material, and how much they learn. The administration is successful, and the students uneducated.
Why don’t we just hand them diplomas on the first day of school, and let the rest be optional?
Relax!
. . . and hit me with that laser beam. Or rather, hit Al, and rip it apart, in slow motion.
Way to go, Frankie.
Rube-y Goldberg Tuesday IV
There's a Party in My Pipette!
. . . and everyone’s invited. Chemistry can be fun, at Creative Review.
The video is funny, and Chlorine has some very nice orbitals, though I’m sorry they stopped before Potassium ripped the water molecule apart.
(And, of course, funny chemistry videos demand a physics rebuttal, which will be forthcoming)