Monthly Archives: March 2013

The Little Refrigerator That Could

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NIST Quantum Refrigerator Offers Extreme Cooling and Convenience

[T]he NIST refrigerator’s cooling elements, consisting of 48 tiny sandwiches of specific materials, chilled a plate of copper, 2.5 centimeters on a side and 3 millimeters thick, from 290 mK to 256 mK. The cooling process took about 18 hours.

One thing not mentioned: this almost certainly does not scale up. It works starting at ~300 mK, but the performance

The cooling power is the equivalent of a window-mounted air conditioner cooling a building the size of the Lincoln Memorial in Washington, D.C

doesn’t mean you are going to be able to build an air-conditioner-sized device and actually cool the Lincoln Memorial, unless you got it down to 300 mK first. (Then we’ll talk)

There's a Catch to This

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Kill Thrill: Watch Animals Capture Their Prey in Slow-Mo

Animals use a variety of strategies to capture prey, some of which clearly kick ass (see the sniper-like archer fish, which spits at flies from underwater). But these strategies are even more awesome when scientists film them and produce super slow-motion replays, complete with awkward faces and outtakes. Here’s a gallery of some of nature’s finest prey-capture instant replays.

Some More Bi-Curious Behavior

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Some time ago I posted some pictures of stress-induced birefringent materials viewed with polarizing filter and a polarized source. Well, I’ve been playing around some more (partly because of the sunstone story).

A quick reminder: birefringence is the effect that of having a different index of refraction along different axes of the material. Linearly polarized light that enters at any angle to the axes will be “broken down” into its two components, and each component will propagate at a different speed, because the propagation speed depends on the index. (This introduces a lag between the two components and for the right thickness, you can get them 90 degrees out of phase, giving you circularly polarized light) Since index also depends on wavelength, this effect will vary for different colors of light. In addition, the amount of stress will vary the amount of birefringence. The end result is that when you filter the outgoing light with another polarizer, you will eliminate any colors depending one their polarization. The transmitted intensity through a polarizer varies as \(cos^2theta \) so anything close to 90º will be strongly filtered out, but wavelengths/colors close to 0º (or 180º, 360º, etc.) will be transmitted. The result is very Rainbowy.

Here’s a petri dish (sans Robert Petrie). It looks like there’s a strong stress point in the upper left, which has sort of radiated through the whole dish.

Here’s a blank from a CD spindle

The black background is because the polarizing filter is crossed with the source (an LCD monitor) and no light gets through which hasn’t been rotated some amount. If I rotate the filter to be parallel, only light which has been rotated close to 90º gets blocked

You can see that the same regions are affected (and unaffected). There’s also an obvious Moiré pattern in this picture, which is aliasing from the digital source and camera.

One other curious thing: here’s a (different) blank CD spindle in from of the monitor with no polarizer in front of the camera

There’s a rainbow, but without the filter! How can that happen?

Reflection polarizes light, so what I think is happening here* is that there is the polarization rotation, and reflection of the cross-polarized light off of the bottom surface. The reflection is weak (only around 10%) but basically because of this effect the material is acting as its own polarizing filter. This polarizing effect of reflection is why sunglasses are often polarized — you preferentially cut out excess glare (from e.g. standing water or the hood of your car) by eliminating the polarized light, but without making the glasses opaque and eliminating all light.

*edit: I looked again and you also see it with transmission through the disk, but only when viewing at a shallow angle. The effect goes away when using an unpolarized source. So the cause is a little more subtle.

Added: another pic (forgot I had these in the drawer), with the polarizer not quite fully crossed, to give the best color on the spoon

The Vanishing Train

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Vanishing train defies space and time

It’s a model train like no other: when it enters a tunnel, it seems to defy the properties of space and time. But of course, what you’re seeing is just an illusion. Do you know what the trick involves?

Doesn’t seem like there’s enough space to have a curved and slanted track, but that may be because one thinks it needs to be carried out within a small space. The train takes almost as much time to emerge from the tunnel as to go around the track, so I don’t think it’s a perspective illusion of the tunnel being longer than it appears. My guess is that there’s a second track below the table. The train enters, veers right and down slightly and follows a large loop below the table, re-emerging inside the tunnel.

Here Comes the Sunstone

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Magical Viking stone may be real

Cool little bit of optics here. Scattered light gets partially polarized, depending on the angle, and will be maximally polarized at 90º from the source. Of course, light can scatter more than once, so this will not result in perfect polarization from the atmosphere.

The researchers said such sunstones could have helped the Vikings in their navigation from Norway to America before the discovery of the magnetic compass in Europe.
They would have relied upon the sun’s piercing rays reflected through a piece of the calcite. The trick is that light coming from 90 degrees opposite the sun will be polarised so even when the sun is below the horizon it is possible to tell where it is.
They used the double refraction of calcite to pinpoint the sun by rotating the crystals until both sides of the double image are of equal intensity.

Here’s a view of the sky at roughly 90º from the sun, looking through a linear polarizer at two orientations — one that blocks the most amount of light and one the blocks the least. You can tell the light is definitely polarized.

Known Knowns

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Science, Morality, Possible Worlds, Scientism, and Ways of Knowing

One interesting subset of the discussion is the ice cream question.

Chunky Monkey is the best possible ice cream.
…
The ice cream question is the one that is closest to the issue of morality. Again, one might suggest that all we need to do is collect neurological data relevant to the functioning of pleasure centers in the brain when one eats different kinds of ice cream, and decide which does the best job. But that’s the question “What effect do different flavors of ice cream have on the brain?” (which is scientific), not “What flavor of ice cream is the best?” (not). To answer the latter question, we would have to know how to translate “the best ice cream” into specific actions in human brains. We can (and do) discuss how that might be done, but deciding which translation is right is — you guessed it — not a scientific question. If I like creamy New-England-style ice cream, and you prefer something more gelato-y, neither one of us is wrong in the sense that it is wrong to say that the universe is contracting. Even if you collect data and show beyond a reasonable doubt that New York Super Fudge Chunk lights up my brain more effectively in every conceivable way than Chunky Monkey does, I’m still not “wrong” to prefer the latter. It’s a judgment, not a statement about empirically measurable features of reality. We can talk about how we should relate such judgments to reality — and we do! — but that talk doesn’t itself lie within the purview of science. It’s aesthetics, or taste, or philosophy.

One thing Sean doesn’t say (possibly because it’s tangential to his discussion) is simply this: as assertion based your ice cream preference is an opinion, and personal opinions — if they truly are opinions — are neither right nor wrong. Where some people go off the rails is when they assert opinions as if they are facts. If you start from the position that “Chunky Monkey is the best possible ice cream” is objectively true, then you’re building a house of cards; the argument is not going to hold up. Yet this seems to happen quite a bit, at least in certain discussions in which I have participated.

Apple in Hell

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Matt Groening’s Artwork for Apple

For anyone unfamiliar, Apple hired Groening to produce illustrations for a brochure about Macs that was aimed at college students. At the time, Groening was best known as the artist of the comic Life in Hell, as The Simpsons has not yet premiered. The brochure was titled, ‘Who Needs a Computer Anyway’ and interspersed Groening’s Life in Hell style illustrations with standard information on Apple’s Mac computers.