The Too-wide Web

For some reason, computer monitors have been getting wider and wider for years. This puzzles me, since like most people, when I'm working, I tend to use tall narrow documents, both to read and to edit. Sometimes I can arrange things so that I have two panels on the screen, which restores them to a more sensible shape, but the Web is a problem. Web pages seem to have begun adapting to wide monitors by adding wider and wider margins, often filled with ads and/or navigation materials. For me, these margins are often too wide for me to use a two-panel setup (it's just a laptop) but often they leave so much width when used full-screen that the text is tiresomely long. Typesetters have a rule of thumb that you shouldn't put more than about twelve words on a line because it's hard to read. Fortunately, I found a Chrome hack that lets me solve the problem.

The RepRap wiki is too wide.

USB Stick

My sister Margaret has a pretty awesome job: in the summers, she works for Fish and Game in Alaska, studying salmon, and (being a government job in Alaska) they pay well enough that she can spend the rest of the year repairing and sailing her boat. There seems to be a great deal of repairing, but one dictionary I had as a kid defined a boat as "a hole in the water into which you pour money". In any case, Margaret has been sailing around the Caribbean; she delivered beans to Haiti in the wake of the earthquake, and she hosted a skill-sharing conference for sailors this last winter. It's an awesome life, and I'm totally envious, but it's a little hard on consumer electronics. Just last year she lost a camera full of pictures (which I totally wanted to see!). So I thought I'd try to make her an indestructible USB stick. I think it worked out pretty well.

Broken centerboard from her dinghy, Scout

Lucky imaging

We have a telescope on the roof of the physics building. It's a fairly nice fourteen-inch Schmidt-Cassegrain telescope, though in fairly rough shape. Unfortunately, the physics building (and necessarily the telescope) is in the middle of downtown Montreal, which is a terrible place to look at the sky: bright lights, clouds, urban heat island, et cetera. So we have a telescope that collects lots of light but doesn't produce very sharp images. My attempt to work around this is described below.

Chemistry at home

YouTube user TheHomeScientist (via In The Pipeline) is posting a series of videos about what you can do in a home chemistry lab; as a nice example, there's this beautiful one about the purification of hydrochloric acid:

Isn't this method elegant? No complicated boiling or fumbling around with strong acids; just take advantage of the fact that HCl is a gas.

I think it's great to show people that you can really do chemistry at home. Science is not just the domain of white men in white coats with PhDs. On the other hand, I'm hesitant to get too ecstatic about how "democratic" this is. Not just anyone can afford the time, energy, and space to set up a lab like this.

Gallium surface gunge

Gallium, as a safer liquid metal than mercury, has two major drawbacks: the surface rapidly acquires a layer of dull oxides, and when in contact with surfaces it tends to leave a thin layer behind. I've been doing some reading to see if I can work around this problem, and I came across this enjoyable article (which may be behind a paywall).

Gallium

Through the magic of ebay, I bought some gallium. It's strange stuff. Apparently whether it's listed as liquid or solid on periodic tables depends on where the table is printed; the melting point is 30°C, so it's solid at room temperature if the room's in Canada in March. But it'll melt in your hand, though it's a slow process.

Gallium is a crystalline solid; I suppose many metals are, but the crystals are really obvious when gallium solidifies. I thought I'd take a video of gallium crystallizing, but it has a tendency to supercool, so after sitting at room temperature for hours it was still liquid. I dropped a crystal of gallium in, though, and I got this beautiful slow crystal formation:

This video is shown at twelve frames per second, each frame is 60 seconds of real time. (It starts when it does because that's when I realized nothing was going to happen immediately; it ends when it does because that's when my camera overheated (!).)

Those vague angular patterns on the surface are actually crystals forming underneath. When I tipped the dish so the liquid flowed away I saw this:


Unfortunately, gallium is directly below aluminum on the periodic table, so, like aluminum, it reacts very rapidly with air, forming a sticky surface scum. When gallium is liquid, though, this scum can't stay in place to protect the surface; instead it sticks to everything around it. Rolling gallium through your fingers feels very peculiar — it's decidedly denser than water, though not tangibly more viscous, and it doesn't feel cool (its vapor pressure at room temperature is tiny). But because of the oxidation, it leaves a gray scum all over your hands. Pieces of gallium left in air also quickly start looking dull and dirty.

Liquid metal

Electromagnetism is complicated. Fluid dynamics is also complicated. For a real headache, though, try working on a problem where both kinds of effect are relevant (sadly, this covers most of astrophysics). Even if you make some simplifying assumptions and get the theory of magnetohydrodynamics, you are still left with all sorts of complicated effects. Leaving aside from the much more complicated equations you might expect, magnetic fields and velocity fields define two potentially different directions at each point, meaning that you can very rarely get away with assuming spherical symmetry to get down to a one-dimensional problem. Nevertheless there are some neat phenomena that occur.

One gadget I'd like to build is a demonstration of is a fluid pump in which the only moving material is the fluid. It turns out there are simple effective designs (PDF) (some of which are in use in nuclear power plants). The biggest problem turns out to be choosing an appropriate fluid.


The basic requirement is that the fluid be conductive. A low resistivity would make the design easier, but as long as the resistivity isn't too high something can probably be arranged. So as I see it the feasible solutions are:

1. Aqueous solution of some sort (e.g. salt water, vinegar). Unfortunately you tend to get electrochemistry happening: the current is carried by the motion of the ions, but as you add and remove electrons at the electrodes you get things like 2Cl^- -> 2Cl^∙ -> Cl₂, which aren't good for your electrodes or your health. You might be able to work around this with a sufficiently low voltage - as I understand it these reactions need a minimum of a volt or so to happen at any significant rate - but supplying power at such a low voltage is awkward. Apparently high frequencies work too - at tens of kilohertz or megahertz the ions don't migrate enough in any one direction to make much difference. But this means you have to use electromagnets, and moreover, electromagnets that work at those high frequencies.


2. Mercury. Liquid metal, nice and conductive. Quite poisonous, at least in vapor form or when reacted with other things. Also very dense (so hard to get moving) and somewhat expensive per milliliter. It's really the poisonousness that's the problem.


3. Wood's metal or "cerrobend". Melts in hot water. Contains a lot of cadmium, which is rather poisonous. Not too expensive. The gadget would need some means of heating to keep the metal liquid; for a demonstration that's meant to run for very long, this means a thermostat and safety systems.


4. NaK. Eutectic alloy of sodium and potassium, liquid at room temperature. More reactive with water than either sodium or potassium. Non-toxic, at least in the subtle environmental sense, though even after the sodium and potassium have reacted with water you're left with concentrated hydroxides which will destroy skin. Might be possible to handle safely under clear mineral oil (but is a fire hazard if ever broken). May wet glass easily, making a sealed arrangement problematic. May be expensive.


5. Galinstan. Eutectic alloy of gallium indium and tin. Liquid at room temperature. Not very toxic (probably safe provided you don't eat it or bathe in it, though oxide dust in the atmosphere is possibly a problem). Wets glass, so it would quickly render a container opaque. Is oxidation an issue? Expensive.

I think the way to go is with galinstan and a fairly small fountain. This conveniently lets you use little permanent "supermagnets". I'd aim for a U-shaped channel, with an electrode in the middle and on either side of the U. I'd have to figure out what voltage and current would be needed, but I could probably arrange to use a few volts at a few amps, which should be easy to get (out of a PC power supply, maybe even). The electrode material is another question - it looks like copper or aluminum would be attacked by the galinstan, but stainless steel should be okay.