Physics — It's Practical!


A few posts back I was concerned with optimising the WiFi reception in my flat, and I chose a simple method for calculating the distribution of electromagnetic intensity. I casually mentioned that I really should be doing things more rigorously by solving the Helmholtz equation, but then didn’t. Well, spurred on by a shocking amount of spare time, I’ve given it a go here.

It turns out that the Helmholtz equation can also be applied to the modelling of the forced vibrations of the square plate, where the choice of conditions above equates to applying a force at the centre of the plate and clamping the edges. The rice/sand/etc settles at the nodes of the plate, i.e. the positions which stay stationary in the oscillation.

Today is Fara Day

Physics demonstrations: Faraday disk

By turning a hand crank, one rotates a copper disk between a pair of magnets (the black disks), one generates an electrical current that runs from the outer edge of the disk to the central axis. Wires connected to these two points runs to the red and black plugs, through which one can measure the voltage difference generated. It isn’t a spectacular amount — I measured about 5 millivolts, max — but it demonstrates the phenomenon known as rotational electromotive force.

Busy and Warm

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While I was out with my FLIR One I noticed some bees pollinating the flowers on a bush and snapped some pics and took the video. They’re a tad warm. Flying is hard work.

One thing I’ve noticed with my camera is that the visible and IR cameras don’t quite line up (I haven’t read the instructions yet, since I’ve been too busy playing, meaning I don’t know if this can be calibrated) So you might see the bee image and the yellow warm blob not quite lining up. I’m pretty sure that’s the alignment issue and not an infrared ghost.

That's So Hot

Finally got my FLIR One thermal-IR camera working (the issue was with the phone to which it’s attached), and it’s amazing.

This is my kitchen sink, with a bowl full of room-temperature water in it, along with some utensils, and the water on hot, aimed so it hits the basin rather than going straight into the drain.

Preceded by Brain Damage

The 2017 total solar eclipse awarded to the United States

Love the title. If you want to skip to the details, go ahead

I remember a partial eclipse that happened when I was in grad school (probably July 11, 1991). It was lunchtime and the gaps between leaves of a tree made for a set of really good pinhole cameras. There were dozens of eclipse images projected onto the ground.

Be eyesafe … in three years (and the rest of the time, too).

A Tiny Bit of Insight into this Navy Scandal

Thirty years ago, right about … nnnnow … I was graduating from Officer Indoctrination School in Newport, RI, and would shortly report for duty in Orlando, FL on the USS Disney World as a Nuclear Power Instructor, where I would serve for a little over 4 and a half years.

So this got my attention: AP NewsBreak: Navy Kicks out 34 for Nuke Cheating

At least 34 sailors are being kicked out of the Navy for their roles in a cheating ring that operated undetected for at least seven years at a nuclear power training site, and 10 others are under criminal investigation, the admiral in charge of the Navy’s nuclear reactors program told The Associated Press.

The number of accused and the duration of cheating are greater than was known when the Navy announced in February that it had discovered cheating on qualification exams by an estimated 20 to 30 sailors seeking to be certified as instructors at the nuclear training unit at Charleston, South Carolina.


A lot of things have undoubtedly changed in the 25 years since I separated from active duty — Nuke School moved from Orlando, FL to South Carolina, and they combined it with the hands-on Nuclear Power Training Unit (NPTU) training taking place on moored submarines (originally done at prototype sites, and two of those units still operate) and the Nuclear Field “A” school for the enlisted, which was just getting started when I was teaching.

The report says this was confined to a single unit and the test was called “engineering watch supervisor” which leads me to believe this happened with the NPTU training portion of the school, which happens at the end of the sequence.

There is mention of there being five tests, given in a predictable rotation. The classroom and prototype training were each about six months (IIRC it was 24 weeks), and that probably hasn’t changed much. Each new class arrived at seven week intervals (except if the start were at the end of December, when classes were not held), which means that there were at most four classes in session at a time. The rationale behind five exam templates was that no active student could give useful information to a shipmate in a subsequent class in terms of test questions and answers, since they would not be taking the same test, and because all test were returned after review — they were never out of an instructor’s control. If the students wanted to come up with a master file, it would be by memorizing question and answers, and then passing the information along, with no benefit to the first five sets of students who did this. Not impossible but also not considered a big risk.

Coming up with a completely (or largely) new exam was not really an option, because you want some degree of uniformity of the difficulty of the tests. So you would recycle the tests with maybe a few changes, and that allowed you to compile statistics on test questions. If a particular class did exceptionally bad or good on an exam, you could have some confidence that it was not because the test was too hard/easy. You could replace questions with others in the exam bank and know it shouldn’t wreck the projected score because you had these stats, and brand-new questions were limited to minimize any effect they might have if they proved to be significantly easier or harder than projected. I don’t really find fault with that — potential staff cheating wasn’t the focus. The staff are/were supposed to have more integrity than the students.

Back in the day, of course, none of this was computerized. We barely had word processor technology, and no exam material could go into any digital format (exam writing was literally cut, copy, and paste. As in cut out a question from one sheet and paste it in place on the new exam master, and run it through the copy machine (sometimes twice, so you could white-out any extraneous lines from the cut). So there’s some inertia here in the rules, from the days when greater changes to the exams were just too laborious to carry out.

The blurb about the reactors being operated safely was valid. The sailors were already qualified to do that — this was for teaching certification, not operator certification, which is one reason why this is puzzling. The information should have been material they knew. In my qualification there were oral exams as well and I imagine that’s true for this part of the program, so any knowledge deficiencies could have been uncovered.

While my nominal tour of duty was four years (I extended it to better mesh with the start of graduate school and because I was in a not-yet-known-to-be-doomed relationship) these sailors likely had shorter tours, so if this has been going on since 2007, the cheating franchise has changed hands a few times. It’s not clear if all 34 are currently instructors, or if (as I suspect, now that I think about it) this is going to include sailors much closer to their retirement.

There’s an unfortunate habit of thinking that integrity is not ratting out your friends, so it’s quite possible that some sailors are getting away with cheating because their shipmates won’t turn them in. The navy integrity and ethics I am used to always had, somewhere in the foundation, the idea that cutting corners was bad because lives were at risk. If these were indeed sailors at the latter part of the training, then they had been to sea, where your life depends on your shipmates not shirking their duty (this is not hyperbole; mistakes made 400 feet below the surface do not have a margin of error you have when you can open a door and run outside), and why such things are not tolerated. That makes this all the more shocking, and it’s also refreshing to see it being made public rather than some attempted half-assed coverup. (Though a more cynical me might speculate that there is a coverup of a larger problem and these are scapegoats, but despite this scandal I’m not feeling that cynical at the moment) This serves as a warning for anyone tempted in the future that it’s not worth it.


What If All The Images Went Away

After arguing with (arguably) allies in science communication I was fed up. Fed up with the attitude that unattributed images are just a (small) sacrifice for the net good of science communication to the populace at large. Fed up that photographers, cartoonists & illustrators are considered by many to be lesser professions than scientists & educators. Fed up that rapid image sharing (oh I’m sorry: “curation”) can trample so many creators and yet lead to fame and fortune.

I found myself saying once again, “can you imagine what science communication would be like without images?

Note well that Glendon Mallow is discussing attribution, which is a minimal effort, and not permission, which really should be a part of the discussion (Here’s a link where that does come up). Sometimes permission is not an issue, because of creative commons licensing or the image being in the public domain. But a lack of a copyright notice is not any guarantee that an image is in the pubic domain some people will edit images to remove the attribution and copyright (OMG!) before they post an image, and you might be grabbing that bootlegged image. The bottom line is that using an image without permission is likely a copyright violation. And it’s the wrong thing to do.

But, baby steps. As noted in the post, this internet doohickey is still pretty new, so lets get the lack-of-attribution habit fixed, and then we can tackle getting permission.