We said that it’s simple, and it is: it’s a brick wrapped in a piece of paper.
If you don’t have a couple of bricks (and we didn’t), they turn out to be cheap at hardware and home improvement stores. These are “cement bricks” — red dyed cement– and cost about $0.25 each. Wrapping them up keeps them from scratching up your shelves and books, but also from depositing cement debris everywhere.
The geek part is on the outside.
The Onion: NFL Scientists Postulate Theoretical Down Before First Down
Citing the extremely low level of entropy present before a normal set of football downs, scientists from the NFL’s quantum mechanics and cosmology laboratories spoke Monday of a theoretical proto-down before the first.
An assassination attempt, with emphasis on ass: the bomb was concealed in the orifice of choice for concealing items. I’d say convenient orifice, but it’s probably not all that convenient.
The bomb couldn’t be that big, and water (being a large fraction of the human body) isn’t very good shrapnel.
While the assassination proved unsuccessful, AQAP had been able to shift the operational paradigm in a manner that allowed them to achieve tactical surprise. The surprise was complete and the Saudis did not see the attack coming — the operation could have succeeded had it been better executed.
We know this wasn’t The Onion because there is no remark about how hindsight is 20-20, mention of a thorough probe of the incident, or talk of a push for new security measures. Or discussion of market penetration of security technology. (Oh, strike that last one. They say it here)
Via Schneier, who cautions us not to tell the TSA.
I don’t generally watch the teen-coming-of-age drama shows, unless forced (as I was on vacation; the episode of Degrassi was a cheap ripoff of Pump Up the Volume without the benefit of a topless shot of Samantha Mathis), but I’m sure this plot has been covered somewhere: Awkward Teen asks the Beautiful Cheerleader to the prom; she has recently split with Handsome Quarterback, but doesn’t immediately say yes to AT, so he assumes she will say no and asks Safety Date, who is much more likely to want to go with him, and she says yes. Immediately thereafter, BC also says yes. Depending on the context, either tremendous angst or hilarity ensues. Possibly both, depending on the quality of the writing.
How does this apply to me? A while back I got an invitation from an old navy buddy to give the keynote talk at the Southern Atlantic Coast Section of the American Association of Physics Teachers Conference. Keynote speakers are typically either famous, to some degree, within either the physics or pop-physics communities, or are attempting to become so by promoting a book, so I am not the Beautiful Cheerleader in this scenario. I figured this was an act of desperation, but I agreed, thinking it would be fun. Lo and behold, it turns out that the other speaker can make it. (Cut to commercial)
All is not lost. I’m getting my own slot during the conference, though that will be a tad awkward — the after-dinner talk (and the public talk that some conferences have) has more leeway in not being directly related to the theme of the conference. I don’t have any particular insight into teaching to share; certainly not an hour’s worth. Same goes for a lot of themes that show up here — I don’t want to make the mistake of trying to turn a 5-minute skit into a feature movie, because it rarely works (are you listening, Saturday Night Live?) So I’ll go with my plan and talk about clocks and timekeeping, with a few cartoons thrown in, and leave the connection to teaching as an exercise for the interested viewer. I was going to do a bit about how I’m at least a little bit famous, and promote the blog, and I may leave that in.
I was also toying with the idea of going with a minimalist presentation, with very few slides in the first part of the talk. The show-and-tell part, though, really needs the “show” as much as the “tell.” Still working on that. I lose the comfort of the “1 – 1.5 minutes per slide” guideline, and since talks will follow mine, there’s pressure to finish on time.
Throwies are simple LED circuits — the LED and a battery, with an optional magnet so they will stick to ferromagnetic materials.
Evil Mad Scientist Laboratories does a pretty exhaustive analysis on the circuits, looking at battery life and potential danger of these simple circuits. Some thoughts on throwies
This data shows a couple of interesting things. First is that the power-law model seems to hold fairly well. Second, the power function that pops out is not very different from that of the data from only the first half hour– integrating both out to 24 hours gives two answers– 150 mAh and 186 mAh –that differ by only 25%. The estimate based on the long data record (150 mAh) is the more accurate one, but this does suggest that we should be able to use the data from the first half hour alone to get a fairly good “factor of two” estimate of the performance over 24 hours.
Entanglement in the Macro World
By linking the electrical currents of two superconductors large enough to be seen with the naked eye, researchers have extended the domain of observable quantum effects. Billions of flowing electrons in the superconductors can collectively exhibit a weird quantum property called entanglement, usually confined to the realm of tiny particles, scientists report in the Sept. 24 Nature.
That sounds pretty cool, though they don’t go into any details about why exposing the currents to microwaves would entangle them. If the microwaves were linearly polarized, and the current loops are acting as antennae, I can see this; linear polarization can be expressed as a superposition of right- and left-circular polarization, so that might do the trick.
However, I have some objections to the reporting.
After interacting in a certain way, objects become mysteriously linked, or entangled, so that what happens to one seems to affect the fate of the other.
This is ambiguous, so I’m not sure if it fall into the trap of the “doing something to one changes the other” error, but even ambiguous is bad. Entanglement means knowing the state of one tells you the state of the other. And the real kicker here is “mysteriously,” which implies that nobody knows what the heck is going on. There are unanswered questions in entanglement, as there are in all areas of science, but it’s not the same as scientists fumbling and bumbling around, saying, “OMG! WTF?” Entanglement is a prediction of quantum mechanics, and the fact that people are exploiting it shows that it’s not really Sphinx-y (terribly mysterious) at all. Physics ain’t easy, but there’s no need to hamstring the understanding of it by selling it as mysterious.
In the new study, researchers used a microwave pulse to attempt to entangle the electrical currents of the two superconductors. If the currents were quantum-mechanically linked, one current would flow clockwise at the time of measurement (assigned a value of 0), while the other would flow counterclockwise when measured (assigned a value of 1), Martinis says. On the other hand, the currents’ directions would be completely independent of each other if everyday, classical physics were at work.
This can’t be right. If they are independent of each other you expect the currents to have no correlation, so half the time they should be in the opposite direction — so simply measuring currents in the opposite direction is not an indication that they are entangled. That could hold only if classically you always expected them to be in the same direction. The indication that they are entangled is the much higher incidence of finding the opposite currents, as was observed.
Volume Packing of Breakfast Cereal
With Raisin Bran, I tend to fill the bowl with cereal, then add milk, and when I finish the cereal, there’s only a small amount of milk left. With Cheerios, on the other hand, after I finish all the cereal from a full bowl plus milk, there’s still rather a lot of milk left. I generally put in another half-bowl (maybe two-thirds) worth of cereal, and finish that, too.
Being a physicist (and, as noted earlier, a gigantic dork), it occurs to me that this can probably be explained by the different volume packing factors for the different shapes. Raisin Bran is mostly flat flakes, which Cheerios are little toroids. Those two shapes will fill space very differently.
To measure ultrafast phenomena, researchers often use repetitive trains of very short laser pulses. For example, they can create two pulse trains from the same source and send them along different paths. To measure the length of the pulses within the trains, they shine both at a “nonlinear” crystal. The crystal produces extra light with double the original frequency when two pulses are present simultaneously. By changing the path followed by one train, perhaps making it a micron or so longer, researchers create a delay of a few femtoseconds. As they increase the extra path length, pulses from the two trains become out of sync, which reduces the crystal’s output and indicates the length of the pulses.
The Poisson/Arago/Fresnel spot, which is a great example of the predictive requirement of science; this one being a binary condition. One implication of the hypothesis is that there will be a spot. Either there isn’t a spot, or there is, and that will or will not falsify the hypothesis.
“If Fresnel’s idea is correct, then the edges of a circular obstruction will act as sources of light waves. Most of these will cancel out and produce a shadow behind the object, as expected. But because the path length from the edge to the middle of the shadow is equal no matter where on the edge you start, the cancellation can’t happen and there has to be a bright spot right in the middle of the shadow. This is self-evidently bogus.”