Physics of GPS relativistic time delay over at Unused Cycles, yet another appears-to-be-new math-y/physics-y blog. Goes through the calculation of the gravitational and kinematic effects on GPS satellites.
Monthly Archives: June 2008
The Cause Of, and Solution To, All of Life's problems
Alcohol ‘cuts risk of arthritis’
The risk was up to 50% lower for those who drank the equivalent of five glasses of wine a week compared with those who drank the least, they found.
The results should be taken with a grain of salt (on pretzels or peanuts, preferably) because the researchers were pretty well liquored-up and the data were analyzed between choruses of “Louie, Louie.”
(and the “standard glass of wine” is one more thing I want to see next time I visit NIST)
Lance Armstrong, Homer Simpson. Homer Simpson, Lance Armstrong.
The object? Consume as many donuts as you can during the “stages” to gain a time bonus. The final stage is a staggered start hill climb up the notorious Torrey Pines Hill. Each donut consumed is worth 30 seconds on the clock during the hill climb and first person to the top wins the jersey the title “Gluttonous Champion” and bragging rights for a full year. Ex: Bob eats the most (10 donuts) while Jim eats only 9. In this case, Bob starts the hill climb first and Jim starts 30 seconds after him.
If it’s the Murderhorn, though, you must consume food that’s in bar form.
They See You When You're Sleeping . . .
Be good for goodness’ sake. Or maybe out of fear of being watched.
A while back I posted about being able to track people using their cell phones. Well, some scientists did a study doing that very thing — “Understanding Individual Human Mobility Patterns” using cell phone signals.
The location of cell phone users was located every time they received or initiated a call or a text message, allowing Barabási and his team to reconstruct the user’s time-resolved trajectory. In order to make sure that the findings were not affected by an irregular call pattern, the researchers also studied the data set that captured the location of 206 cell phone users, recorded every two hours for an entire week. The two data sets showed similar results, the second validating the first.
No need to have the NSA insert that GPS transponder chip under your skin, after all.
Physics Buzz ponders the ethics of the study
I'm Baaack
Power was restored just a few minutes ago and now I’m getting my blog fix. Some big frikkin’ trees went down — I just took a stroll to slay some food (I found many tracks; they lead to a place the locals call Mac-doh-nalls. Plentiful hunting, but I don’t think the walk negates the damage of eating there. Heavily salted fat. Yum. Still, with traffic lights still out driving was insane, so that was the only option) Anyway, the damage was impressive. Power was out somewhere around 28 hours, so the food in the fridge goes. The USDA says a full freezer is good for 48 hours, but a half-full one is only 24.
Grading Policy, Sir!
Dr. Pion’s blurb about exam design and grading reminded me of a few things. I taught for the Navy in the nuclear power program, long ago, when the school was in Orlando, Fl; physics, which included applications to plant operations whenever possible, and a class on principles of reactor operation. There are some distinct differences between exams in this context, vs how they were graded when I was a TA. Being in the military means never having to say you’re sorry to students or even explain yourself to them, if you don’t want to. That translates into not having to post or explain the grading policy on exams; the students’ job is to ‘learn the material, dammit,’ not to haggle for points on exams. Students could still put in for regrades, but it had to be for an obvious grading error, rather than for a dispute about how many points should have been deducted for their mistakes. That didn’t stop all whining, but it’s certainly a bonus when you can tell the offender to shut up — in navy parlance, “Secure that!” (or, “Secure that shit!” Optional for officers, pretty much mandatory for senior enlisted)
Since the material had a definite application, answers to questions had to display an appropriate level of understanding, which was a factor that could supercede any other policy that had been set up. There was a shorthand for the various types of errors — the usual suspects, like math errors (ME) or sign errors (SE), and the big red X for anything wrong, but there were others, too, in part because there were always several “discussion” problems, even on physics exams:
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Powerless
Nasty storm hit yesterday, and there was no power when I got home . . . and none when I got up. Looks to be a tree down on the street, and I’m guessing it took the power line with it, and no opportunity to fix it in the dark. No lights, no hot water. Fortunately my normal morning routine is to shower at work, after going to the gym, so the latter issue didn’t bother me, but it also meant discovering that a desk is only an approximation to an ironing board. And that none of the activities in which I partook this A.M. are more fun in the dark.
Nano-cooties
How else to explain Super-Repellant Surfaces
The surface, made up of silicon spikes just 400 nanometers wide, physically repels a wide variety of liquids, including water, oil, solvents and detergents.
Especially anything named “Ethyl”
As Long as I'm in the Neighborhood . . .
Titanic Was Found During Secret Cold War Navy Mission
Ronald Thunman, then the deputy chief of naval operations for submarine warfare, told Ballard the military was interested in the technology—but for the purpose of investigating the wreckage of the U.S.S. Thresher and U.S.S. Scorpion.
Since Ballard’s technology would be able to reach the sunken subs and take pictures, the oceanographer agreed to help out.
He then asked the Navy if he could search for the Titanic, which was located between the two wrecks.
Since the bulk of the US Navy’s nuclear fleet has been subs, most of the students I taught were destined for subs, and many of my shipmates who had done tours at sea had their dolphins. That experience piques my interest even more when stories such as this pop up. (My own brief trip on a sub was enough to seal the deal that I wouldn’t be doing that for a living. 6′ 3″ with a touch of claustrophobia wasn’t going to mix well with most of the subs active back then)
For some more discussion of the Scorpion accident, and how the location of the sub was eventually determined, I recommend Blind Man’s Bluff by Sontag and Drew. There are also stories about Project Jennifer, a mission to retrieve a Russian sub, as well as some other very interesting submarine-related espionage activities.
Can't . . . Avoid . . . Collision
Remember the conservation-of-momentum problem you did in 1st semester physics, where the projectile breaks into two pieces at the apex of its flight? Now multiply by Avogadro’s number (and then an additional order of magnitude or more)
Momentum’s conserved, even in slo-mo.