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Category Archives: Tech
Smile! You're on Wifi Camera
The Wifi Camera is a camera that takes “pictures” of spaces illuminated by wifi in much the same way that a traditional camera takes pictures of spaces illuminated by visible light.
The camera reveals the electromagnetic space of our devices and the shadows that we create within such spaces, in particular our wifi networks which are increasingly found in our daily lives, in coffee shops, offices and homes throughout cities of the developed world.
I See What You Did There
Sound can leap across a vacuum after all
I saw this retweeted by Jennifer, but sorry — No, it can’t.
When a sound wave reaches the edge of one crystal, the electric field associated with it can stretch across the gap and deform the crystal on the other side, creating sound waves in that second crystal (Physical Review Letters, vol 105, p 125501). “It is as if the sound waves don’t even recognise the vacuum – they just go through,” says Prunnila.
This is the kind of writing that really, really annoys me. Redefining terms in order to sensationalize the material. Sound doesn’t jump across the vacuum barrier — an electric field does, and that’s perfectly cromulent. The electric field causes the piezoelectric transducer on the other side to vibrate and recreate the sound. Neat. But if this counts as sound going through a vacuum, then transmissions using a satellite has to count, too. We’ve been doing this for more than 50 years.
Evil Genius Physics
French Thieves Use Vacuums to Suck Thousands from Safes
The key to the thieves’ nearly uninterrupted streak of success, per French reports, is the way that Monoprix delivers money from the checkouts to its safes: Envelopes of cash are funneled in via pneumatic suction tubes. Whereas breaching the safe itself might be considerably difficult, requiring explosives or safecracking, the thieves realized that if they just drilled into the delivery tubes near the safebox and hooked up a powerful vacuum, they could suck the money out and get at it much more easily.
I don’t know the specifics, so there may be a good reason that they haven’t fixed this problem during the four years the thieving has been going on, but it would seem a check valve would be useful here.
Is This the Party to Whom I Am Speaking?
Once the Rockets Are Up, Who Cares Where They Come Down?
… “That’s not my department,” says Wernher von Braun. (Tom Lehrer)
The Quadroheckicopter
My Pen Crashed
The pens perform an interesting trick: when Dervishaj and her classmates write in their notebooks, the pen records audio of whatever is going on around it and links the audio to the handwritten words. If her written notes are inadequate, she can tap the pen on a sentence or word, and the pen plays what the teacher was saying at that precise point.
Dervishaj showed me how it works, flipping to her page of notes on exponents and tapping a set of numbers in the middle of the page. Out of a tiny speaker in the thick, cigar-shaped pen, I could hear her teacher, Brian Licata, explaining that precise problem. “It’s like having your own little personal teacher there, with you at all times,” Dervishaj said.
Chirp
Finally signed up for “The Twitter.” When I first learned of it, I thought it would just be a compendium of noise, since the threshold to tweet is so low. And this is precisely why I don’t do Facebook very much — I am just not all that interested in the level of minutia of my friend’s lives, and I shudder to think they are that interested in mine (or feel that they’re missing out because I don’t post such trivialities very often). But today I found out that Steve Martin is tweeting, so I signed up to follow that.
I don’t want it to be a collection of “Boy, I could use more fiber in my diet” or “De-linting my belly button!” tweets. On the other hand, I do have these random thoughts, which I occasionally blog. That’s the kind of stupid stuff I’ll probably tweet. Probably.
I understand it’s protocol to follow those who follow you, but … no. I’m not going to return the favor in order to be a statistic, or even to be polite. I am a physicist, and have no social skills. Follow only if you have some slight possible interest in the content.
The Needs of the Many Outweighs The Needs of the Few
Self-organizing traffic lights
The key is that this kind of control does not fight the natural fluctuations in the traffic flow by trying to impose a certain flow rhythm. Rather, it uses randomly appearing gaps in the flow to serve other traffic streams. According to their simulations, this strategy can reduce average delay times by 10%–30%. Remarkably, the variation in travel times goes down as well, although the signal operation tends to be non-periodic and, therefore, less predictable. You can’t say precisely how the lights will go on and off, but you can be sure your drive will be shorter.
So it sounds like if you’re in a dense group of cars, you’ll see more green lights, but if you are alone or in a sparsely bunched group, you’re likely to get a red, Which bunches you up, et cetera, et cetera. IOW, opposite of the way lights seem to run.