How Does Calculus Compare?

Your math teacher, Darth Vader. (Boy, is he strict!)

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The ability to calculate the length of the hypotenuse is insignificant next to the power of the force.

I have to add — I would have noted that Vader’s board skills leave something to be desired, but he might have found my lack of faith to be disturbing.

Print! Cut! Fold!


Papercraft toys.

Most of the Cubeecraft designs have interchangable parts! Do you think the Rocketeer should be wearing Master Chiefs helmet instead? Go for it. Do you think Mr.Stay Puft should trade in his kerchief for a suit? Switch out his body for Mr.Dtoids!

via Neatorama

Dropping the Minus Sign

Or, in this case, the “not”

Why aluminum should replace cesium as the standard of time

The technique involved is neat: for some atoms you can find wavelengths where the AC Stark shift is the same for the two levels in the clock transition, so the atom is unperturbed by the presence of the trapping light. So you trap them in an optical lattice, with confinement like a far off-resonance dipole force trap (FORT). This means you can continue to confine the atoms while it is in the superposition where it is oscillating between the two clock states.

The big advantage of this method is that you can trap millions of atoms easily in an optical lattice and that should make such a clock much more robust than a fountain, while achieving at least the same kind of accuracy.

Actually, that’s not the big advantage. Fountains trap millions of atoms (even billions, depending on your collection technique). The advantages are that you’d keep that many atoms (fountains lose signal from the original collection because the cloud spreads out, so the number you toss is an order of magnitude bigger than the number that return), you can interrogate the atoms for a longer period of time (an advantage shared by ion trap clocks/frequency standards) and avoiding cold-collision frequency shifts (atoms in close proximity tend to interact strongly, as they can interact for a relatively long time, and this changes the state of the atom, introducing an error in the signal)

However, “at least the same kind of accuracy” isn’t enough. I’ve noted before that international standards are a political issue. Cesium beam standards are commercially available. Furthermore, dozens of labs have or are building fountains, at some investment of time and money to gain the expertise in doing so (because atomic fountains are not, nor are they likely to become, a commercially available item). The countries doing this will likely be reluctant to switch to a standard that requires even more money and acquired expertise in a new technique for marginal gain in accuracy and precision. Especially in light of how many new options for secondary standards have emerged in just the last decade — an even better candidate may emerge as technology advances.

But Don't Put Us in a Home


Fall 2008 Schedule

Teachers Registration: Now – Sept. 8 (or until full)
Physicist Registration: Sept. 9 – Sept. 15 (or until full)
Teachers adopt physicists: Sept. 16 – Sept. 23
Discussion forums open: Sept. 29 – Oct. 17

This effort is led by Sigma Pi Sigma, the physics honor society, and aided by American Physical Society and the American Association of Physics Teachers. Technical support is through the ComPADRE Digital Library.

I did this two years ago, and a colleague did it last year; it sounded like the format had evolved to be a little more interactive. When I participated, I was given a list of questions, the students chose a subset to ask, and it was done through email via the teacher. Now it looks like there is a discussion forum, with more freeform interaction.

Full Disclosure

Full Disclosure and the Boston Farecard Hack

This preference for secrecy comes from confusing a vulnerability with information about that vulnerability. Using secrecy as a security measure is fundamentally fragile. It assumes that the bad guys don’t do their own security research. It assumes that no one else will find the same vulnerability. It assumes that information won’t leak out even if the research results are suppressed. These assumptions are all incorrect.

The problem isn’t the researchers; it’s the products themselves. Companies will only design security as good as what their customers know to ask for. Full disclosure helps customers evaluate the security of the products they buy, and educates them in how to ask for better security. The Dutch court got it exactly right when it wrote: “Damage to NXP is not the result of the publication of the article but of the production and sale of a chip that appears to have shortcomings.”