Tag / physics

by Roslyn

SICB Portland

Here is the poster we presented at SICB Portland last week on the biomechanics of peacock displays (click to enlarge):

SICB poster

I think it turned out pretty well, although I’m not sure it could stand alone without an interpreter.

We had a constant stream of awesome visitors. My coauthor Suzanne brought feathers and a model peacock to demonstrate what we were talking about – brilliant! We also had a touchscreen mounted to the left of the poster to display the supplemental videos, but to my surprise we didn’t use it much. It was too slow to load for every new visitor, although it did come in handy for people who wanted an in-depth look. I realize now that videos should really be integrated spatially with the poster content. This could be done if whole display was a touchscreen, for example.

One of the highlights of the meeting was seeing how folks in Stacey Combes’ lab are tracking the movements of individual bees by gluing tiny QR codes onto the bees’ backs (the codes are automatically recognized on video of the bees entering and exiting their hives by tracking software). Another highlight was Ken Dial’s talk about the influence of predation on the development of flight in nestling birds. Portland had lots of good food and drink and exciting views of 1000s of crows roosting late at night downtown.

Thanks to Owen, Suzanne, Jim and Bob for such a fun project!

by Roslyn

Quirks, quarks and quantum sailboats

An old mystery from my days as a sailor resurfaced this week. Does air on one side of the sail somehow know what the air on the other side is doing? Sounds strange, but it happens to be a key part of explaining how boats, birds and airplanes work, and it stumps a whole lot of people who should probably know better – including most pilots.

I was reminded of this by Bob McDonald from CBC’s Quirks and Quarks radio show. He was in town to give a talk on “The Science of Everyday Life”. It was clear that this was going to be a show for kids, but I dragged Charlie along for two reasons. First, I was planning on presenting some of my peacock research at a family science festival on Saturday; I thought it might be useful to see a master of this sort of thing in action. Fandom came into it too – the Quirks show is one of a handful of radio programs that got me through my troglobite period of 8 hour days in the darkroom last summer.

I was pretty sure what we were in for – baking soda and vinegar magic for the edification of the grade school set – but I wasn’t prepared for how quickly McDonald would put me under his spell, too. Sitting there cold and hungry in the dingy auditorium, I had forgotten all about my surroundings by the time McDonald was whirling a mop around and keeping a kid trapped in his chair using only his thumb to demonstrate centre of gravity. And he was just getting started. Although the talk was too long at nearly 2 hours, it was worth the wait to see video of McDonald’s adventures in weightless flight at the end. His imaginative pitch for the space tourism industry was another highlight. I was hooked at his concept for a giant rotating space hotel. If we put a cylindrical swimming pool smack in the middle, the water would stick to the outer walls by centripetal forces. You could literally fly around in the air at the zero-gravity centre and dive down in any direction to the water below.

McDonald mentioned something in his explanation of how to make a better paper airplane that brought up an old problem for me.

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by Roslyn

The ancient mariner

I drove a tractor for the first time a few weeks ago, when we were furiously collecting the last of the sap run for maple syrup. A small triumph for me since it seemed so terrifying at first. Trying to hide my confusion, I waited until the last moment to ask, “Which pedal is the brake, again?” Both of them? Right. No chance for a screw up, so I charged ahead. It only took until my second trip – with shouts of “Slow down!” from the trailer behind – for me to figure out why those two brakes weren’t working so well. Turns out that the hand throttle was the missing part of my pedal equation.

Locomotion does not come naturally to me. It does, however, for a huge variety of other living things. Powered flight evolved several times in the history of life: at least once in the ancestors of birds, and separately in insects, pterosaurs and bats. Human inventors have had a much harder time with it: unlike animals, we haven’t progressed much beyond our earliest working designs. Orgel’s second rule applies:

“Evolution is cleverer than you are.”

Thinking about this made me realize that the situation today, where most of us are more familiar with human-engineered forms of locomotion than we are with the natural examples, is kind of strange. For most of our history, the inspiration to look for new ways to get around probably came from seeing it done in nature.

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by Roslyn

Dating the rainbow

Buttermere Lake, with Part of Cromackwater, Cumberland, a Shower

The truth is beautiful in Buttermilk Creek. That was the Texas site of a recent major archaeological find. In the village of Salado, just a couple hundred metres downstream from an important cache of artifacts of the early American Clovis people, anthropologists uncovered something just a few centimetres deeper1. In geological terms, that usually means older – and the assortment of stone tools found by Mike Waters and his team might be the definitive evidence needed to overturn the longstanding “Clovis first” theory.

“Clovis first” is the idea that North America was initially populated by a group of big game hunters known for their interchangeable fluted spear tips – a portable tool that fit well with the nomadic lifestyle. I won’t get into the details (see elsewhere), but many researchers now believe that other migrant groups arrived from the north well before Clovis domination. For example, fishing tools found in California’s Channel Islands provide evidence that a seafaring clan made its way south by hopping along the coastline2.

I also won’t cover the Buttermilk Creek find (again, see elsewhere for this). But there is a poetic element to this discovery worth sharing. The proof that the Buttermilk Creek people arrived ahead of Clovis hunters comes, not from the usual radiocarbon dating methods, but from dating the rainbow.

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by Roslyn

Employed science

It’s when applied science gives back, contributing a piece to the basic research puzzle.

Jaded grad students like me get a warm fuzzy feeling when we hear about people reaping unexpected benefits – economic or social – from the results of pure science. Last night I was reminded that this can work in the opposite direction.

Matthew Mecklenburg and Chris Regan, two physicists from UCLA with interests in quantum theory and its applications for sustainable energy, wanted to design a better transistor. Instead, they discovered something fundamental about the structure of the universe1. Hidden from our eyes and our finest instruments, the space that surrounds us might be more like a chessboard than a continuous expanse.

Mecklenburg, a grad student, was investigating graphene as a potential material to make more efficient transistors – the little bits of silicon that allow computers and essentially all modern electronic devices to function. He needed some precise measurements of the way light interacts with graphene at the nanoscale, to assess feasibility of the new design. These experiments gave Mecklenburg a quantitative picture of the way electrons hop around in the lattice of carbon atoms in graphene. And that’s when the chessboard struck.

Mecklenburg and Regan realized that the hopping behaviour of electrons in graphene was formally equivalent to what happens when an electron flips its “spin” – a theoretical concept that has remained an enigma since it was described in the early 20th century.

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by Roslyn

Honed

We brought home a new kitchen knife from my parents last month. The knife block was full, but Charlie exchanged the new one for what was previously our smallest and dullest. He wasted no time wrapping the old one up in plastic and hiding it from me. My hand naturally gravitates towards whichever tool will fit nicely inside it, even when I’m cutting a monster squash. We have a good arrangement: Charlie keeps the knives sharp, I keep my fingers, and I toss him the odd carrot slice in return.

But could he eventually be replaced by a sea urchin? A new study in the journal Advanced Functional Materials explains how sea urchin teeth never dull or break. In fact, they get sharper with use1.

Most people are probably familiar with sea urchins as the spiny little balls one occasionally encounters on the beach. Evil looking, but mostly harmless, so long as you avoid stepping on them. Sea urchins live in shallow tidal pools, eating algae and other plant material. So why do they need such sharp teeth? Much like their spines, the teeth probably serve a protective function. The urchins use them to chew burrows, often in solid rock, where they can take shelter from predators and waves.

In the current study, a group of physicists and biologists used an arsenal of sophisticated imaging, chemical and nano-scale stress test procedures to investigate the teeth of the California purple sea urchin (Strongylocentrotus purpuratus). Like starfish and sea cucumbers, urchins are members of a group of animals known for their penta-radial, or five-fold, symmetry. They have five teeth arranged in what is known as Aristotle’s lantern.

Aristotle's lantern

Aristotle’s lantern, as viewed from below with teeth closed. From Killian et al. 20111.

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