Archive for March, 2013

You'd Better Put Some Clothes on That Naked Singularity, Buster

In case you missed it, an Idaho biology teacher was recently under scrutiny for the unforgivable act of saying the word “vagina” in a class on human reproduction. (To add insult to idiocy, or idiocy to insult, the superintendent says “It is highly unlikely it would end with his dismissal. Maybe a letter of reprimand from the school board.” WTF?)

Anyway, Frank Noschese has a physics-related commentary, in the form of a letter about part of the physics curriculum: Dear Parents. It’s not often I file things under both physics and satire. The section on “Giggle-inducing Scientific Terminology” is absolute gold.

There Are Four Lights!

Illusion of the Week: The Coffer Illusion

How many circles do you see?

Goldilocks and the Laser Pointer

Most Laser Pointers Are Too Strong

This seems a little … unfinished.

Neither the story nor the referenced study mention if the lasers are all supposed to be 5 mW and thus class IIIa (or 3R), or if, as one link claims, there are higher-power lasers that aren’t limited by this threshold because they aren’t marketed as laser pointers. Or if the violation isn’t that they are claiming 5 mW and exceeding it, but rather they are incorrectly (and presumably illegally) calling the more powerful devices laser pointers and listing them as class III/3R.

Then there was this claim.

Green lasers use a shorter wavelength of light than red ones, making them brighter and more dangerous.

This was lifted from the included link, but lacking the detail found in another link. Green lasers aren’t brighter simply because they have a shorter wavelength. If that were true, a blue laser would be brighter still, and they aren’t. In fact green lasers must fire fewer photons per second at you than red lasers do, if they all have the same power. What makes the green brighter is your eye. The eye’s response to light isn’t constant across the spectrum — it’s much better at absorbing (and thus detecting) green light then either red or blue, so the green light has a better chance at doing damage.

Pew! Pew! Pew! … Splash!

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Speaking of lasers, just a navy laser (not a 5 mW laser pointer) shooting down a drone. Mars rovers don’t have a monopoly on laser fun.

Seeing Red. Or the Opposite.

Why Do Doctors Wear Green Or Blue Scrubs?

Green could help physicians see better for two reasons. First, looking at blue or green can refresh a doctor’s vision of red things, including the bloody innards of a patient during surgery. The brain interprets colors relative to each other. If a surgeon stares at something that’s red and pink, he becomes desensitized to it. The red signal in the brain actually fades, which could make it harder to see the nuances of the human body. Looking at something green from time to time can keep someone’s eyes more sensitive to variations in red

I’ve noticed the opposite effect in the lab; when I work with lasers I wear laser safety glasses, which block the wavelength being used, and for quite a while this has been in the NIR. The glasses block everything above ~650 nm, so the glasses look bluish-green and deprives your eyes of any red light. After taking them off, everything has a pink hue to it.


Antiprotons Reflect a Magnetic Symmetry

Physicists have improved the measurement of the antiproton magnetic dipole moment, further narrowing how close to identical it is in magnitude (with opposite sign) to the proton value. I ran across a number of poor articles describing this experiment, all obviously cribbing from the same press release. One mentioned magnetic charge, another claimed that that the experiment determined the charge of an antiproton and seemed to confuse the Penning trap and the proton beam at the LHC. One put the emphasis on the act of trapping antiprotons, as if this had not been done before (it has).

This is a good one. There’s also a link to the free PRL.

[The ATRAP collaboration] look for a difference in the magnetic moments of the proton and antiproton. To enable this test, they precisely measure the magnetic moment of a single, trapped antiproton, achieving the most sensitive measurement to date of this quantity. They compare their result to the known value of the proton’s magnetic moment and find that the magnitudes are equal within experimental uncertainty, as predicted by the CPT theorem. Though there have been other tests of CPT with better precision overall, the work reported by ATRAP improves the limits on CPT violation in the difference of the proton and antiproton magnetic moments by nearly three orders of magnitude

Won't Get Fooled Again

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Einstein is so clever.

Is This Anything Like Prince Albert in a Can?

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Cool slow motion to show off the result of the physics.

There's Always Room

Han Solo “frozen” in Jello

Easter Island statue

This is with 25% less water than the normal recipe, but the forms are still not quite stiff enough and tend to fall apart when I take the out of the tray. Also, not holding up well to handling. More experimentation after I, um, dispose of this work.

Bad News on the Doorstep

Joe over at It’s Okay to be Smart, hates waking up to bad news, in this case the news that NASA is dialing back some of their outreach due to sequestration budget cuts. I have already noted that the GOP was shocked, shocked! that the White House was canceling tours so that they could deploy secret service agents, and that (IMO) the Smithsonian was making a tactical mistake by hiding the effect of their cuts and crippling their future.

While I hate to see it happen, I think it’s the proper course of action, so that the voters can see the effect of a dysfunctional congress.

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