The Tipping Point

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There’s a neat effect just after the 2:00 point of this video: the pilot does a barrel-roll, and the beverage in his cup does not spill. Then, he pours iced tea into his cup while doing the maneuver. The beverage in the cup remains pretty much parallel to the support the whole time.

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The physics here is the same as with a swinging bucket; one must realize that the plane isn’t simply rotating along its axis — it’s following a circular path, and there is always lift (i.e. a force) going from the bottom of the plane to the top. I recreated this (to an extent) with a clear container and some Romulan Ale (I only use it for medicinal purposes). The first frame is where I was holding the bottle, so it’s at rest. The liquid is clearly at an angle to the container, and is parallel with the floor.

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And the second is while the bottle is a freely swinging pendulum, and you can see the liquid is now level with the bottom of the container.

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Blah, blah, blah. Oh, balls. I was working on this a while ago and now find that Rhett has a post up about it, though not following the same path I was going to take. Pouring tea in a plane – upside down, where he’s worked out all of the physics, with diagrams and pictures with circles and arrows and a paragraph under each one explaining what it is. So I’ve abandoned my v/2 (half-fast) explanation in favor of a link to his.

A Matter of Perspective

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Mindset List for the Class of 2014

The class of 2014 has never found Korean-made cars unusual on the Interstate and five hundred cable channels, of which they will watch a handful, have always been the norm. Since “digital” has always been in the cultural DNA, they’ve never written in cursive and with cell phones to tell them the time, there is no need for a wrist watch. Dirty Harry (who’s that?) is to them a great Hollywood director. The America they have inherited is one of soaring American trade and budget deficits; Russia has presumably never aimed nukes at the United States and China has always posed an economic threat.

…

– John McEnroe has never played professional tennis.

– Clint Eastwood is better known as a sensitive director than as Dirty Harry.

– They never twisted the coiled handset wire aimlessly around their wrists while chatting on the phone.

– Woody Allen, whose heart has wanted what it wanted, has always been with Soon-Yi Previn.

… gettin’ old …

What's Eating You?

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A Lecture On The Psychology of Animals Swallowed Alive

From 1925

[Darwin] states that big sharks swallow the porcupine. fish, and has frequently found it floating alive and distended in the stomach of a shark. On one occasion a porcupine fish swallowed by a shark had eaten its way out, not only through the coats of the stomach, but through the walls of tlhe body, and thus destroyed its captor.
Darwin asks, Who would ever have imaginied that a little soft fish could have destroyed the great and savage shark? The diodon iniflates itself with air and water, which it expels with some force when it deflates. The jets of water must cause some curious ticklings to a shark with a lively diodoni in its stomach!

Turning, Turning, Turning Through the Years

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Physicists say cosmic rays affect the length of day

I’d like to add a warning to this (along the lines of the Journalism Warning Labels by Tom Scott): Article title implies much more certainty than the article; the article is more restrained than the title would indicate, and the paper (at least the abstract) even more so. Changing the angular momentum of the earth would affect the moment of inertia, but the correlation here is with the sunspot cycle — the connection to cosmic rays is more tenuous.

The abstract actually says

We conclude that variations in mean zonal winds are modulated by the solar activity cycle through variations in irradiance, solar wind or cosmic ray intensity.

I’ll have to consult my local experts on earth rotation and get their opinion on this.

Overheard in the Hallway of the Day

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I may be posting more “overheard” stories in the near future; we’re in the phase where we’re assembling all of the parts we’ve been working on, more or less individually, so there’s a lot of team activity, which leads to a lot of chatter. Working alone leads to chatter, too, but that’s more cursing Microsoft or muttering about my own mistakes, usually in that order.

I had rearranged the power cords to segregate the modular ones which plug into equipment (i.e. NEMA M at one end, IEC F at the other) and the ones with exposed wires you could wire into a homemade box (or replace a permanent cord) and mentioned this in the hallway. One colleague termed those “power cords of death,” at which point another went all knifey-spooney, “That’s not a cord of death!”

From his lab:

Power cord of death: a power cord with prongs (i.e. male connectors) on both ends. It was apparently used to daisy-chain power strips together, where one had a bad cord on it. Since they’re just wired up in series, you can do this, but you run the risk of wiring a hot receptacle to another hot receptacle, at which point you might have fried grad student. And they don’t often smell good before frying, so that’s a bad thing™.

Son of power cord of death: this was a power cord, sans grounding plug (snipped off), wired into a cable with a BNC connector at the far end. Used to power a fan acting as a chopper in a vacuum system, and the only available vacuum feed-through was BNC. Proving the old adage that when all you have is a BNC feedthrough, all of your electrical problems look coaxial. (Also proving that most professors won’t spend money on new equipment if the old equipment can be kludged together to do the job)

One Ringy-Dingy

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The Virtuosi: Ringing A Bridge

When you strike a bell, it rings at a given frequency. This frequency is called the resonant frequency and is the natural frequency at which the bell likes to ring. Just about anything that can shake, rattle, or oscillate will have a resonant frequency. Things like quartz crystals, wine glasses, and suspension bridges all have a resonant frequency. The quartz crystals oscillate at frequencies high enough for accurate timekeeping in watches, the wine glasses at audible frequencies to make boring dinners more interesting, and bridges at low enough frequencies that you can feel it when you walk. It is the resonant frequency of bridges that we decided to measure.

Looking at Teaching as a Mature Industry

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Why Does College Cost So Much?

They’re promoting an upcoming book, so the article is merely a summary, but from it arises an interesting premise: education is not an industry that benefits greatly, efficiency-wise, from technology. And that’s an interesting point. If there is a limit to how quickly a student can absorb knowledge, and I think there probably is, then any teaching efficiencies you might gain by adding technology are limited, and certainly won’t scale the way it does in other industries, where you might be able to automate processes and eliminate positions and have the potential to reduce costs.

Technology certainly helps the student; I shudder to think of what writing a thesis would have been like without a word processor program, having had the undergraduate experience of writing papers on an electric typewriter and concocting exams in the navy back when they were much more computer-phobic (cut-and-paste was a literal action, not a mouse-click). But that’s not going to get more information into their collective heads in a fifty-minute lecture, or make them read a book faster. It certainly doesn’t scale according to Moore’s Law.

Computers and peripherals (e.g. processing power, storage, networking) are deflationary. The price of all of the related hardware has been roughly constant over the years — and that doesn’t even reflect inflation: it still costs about a thousand dollars of today’s money to buy a middle-of-the-road computer, a few hundred bucks for a monitor, and another hundred for an external hard drive. But the increase in computing power, sizes of monitor screens and capacity of hard drives has been huge. That helps hold down costs in a lot of places, but if it can’t help the professor teach a class, it’s not going to hold the cost of instruction to the level of inflation. Not until you have robotic teachers, at least.