Category Archives: Physics

Turns Out There's a Third Option

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Taking The Temperature Of A Dinosaur

A team of researchers led by Robert Eagle, a biologist at the California Institute of Technology in Pasadena, California, found that rare, heavy isotopes of carbon-13 and oxygen-18 clump together differently depending on temperature.

“It’s basic thermodynamics: At warmer temperatures, you get a more random distribution of these isotopes with less clumping,” Eagle said. “As temperature decreases things slow down and you begin to see more bonding.”

When this bonding takes place within an organism, such as in the formation of the mineral apatite to form tooth enamel, the pattern of bonds preserves a record of the animal’s body temperature, within a few degrees.

Jokes

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Helium walks into a bar. The bartender says, “Sorry, we don’t serve noble gases here.”
Helium doesn’t react.

The bartender tries to take one of Helium’s electrons, but fails.
The Helium is nonplussed.

A superconductor walks into a bar. The bartender says “we don’t serve superconductors here.”
The superconductor leaves without putting up any resistance.

To get to the other side.
Why did the tachyon cross the road?

Schrödinger’s cat walks into the lab and says, “This experiment scares me half to death.”

An infinite number of mathematicians walk into a bar. The first orders one beer. The second orders half of a beer. The third orders a quarter of a beer. The fourth orders an eighth of a beer.
The bartender says, “Screw you!” and pours two beers.

A termite walks into a bar, looks around, and asks, “Is the bartender here?”

We're Gonna Need a Bigger Monitor

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Solar System to scale

This page shows a scale model of the solar system, shrunken down to the point where the Sun, normally more than eight hundred thousand miles across, is the size you see it here. The planets are shown in corresponding scale. Unlike most models, which are compressed for viewing convenience, the planets here are also shown at their true-to-scale average distances from the Sun. That makes this page rather large – on an ordinary 72 dpi monitor it’s just over half a mile wide, making it possibly one of the largest pages on the web.

Oblogligation

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sciencegeekgirl: The Magic of the Middle Division: Changing classroom norms (#aaptsm10)

There’s just one more talk that I wanted to share with any of you who couldn’t be there – another delightful presentation from Corinne Manogue of Oregon State University. Corinne is a colleague, we’ve both been working on creating new activities for use in physics courses beyond the introductory courses, though I’ve been focusing on the junior years and she’s firmly planted in the sophomore level. Still, I’ve used many of her activities from the sophomore level to enhance our junior course, and I just find her approach inspiring.

I took a “math methods of physics” class from Corinne (er, Prof. Manogue) back in the day, hence my feeling of oblogligation to link to a post about her.

Tripping Down the Streets of the City

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New “Wind Lens” Turbine Magnifies Wind For Increased Power, Reduced Noise

There are a number of stories about this, and for most of them the technical explanation starts and ends with “The structure works similarly to a magnifying glass that intensifies light from the sun — except in this case, the lens intensifies wind flow” or something similar. Which is really frustrating. This story doesn’t, and even provides a link to the university web site, so perhaps we can glean additional information from that.

OK, it looks like this “lens” is a venturi of sorts. I’m neither a fluid mechanic nor an aeronautical engineer; I imagine the compressibility of the air makes this a little different for air than for water. But when you restrict the area of flow, the speed increases. Put another way, by funneling/focusing you increase the energy density of the air, so more energy is present within the area of the turbine and you can extract more energy without making the blades bigger. That much I get. I’m not sure if this accounts for all of the increased efficiency or if there are other effects as well, like improved efficiency by generally having higher speeds. It certainly doesn’t look like you are tripling the capture area from the pictures.

The stories tout this as being great, but I notice that the turbines are ~1 kW, as opposed to commercial turbines which are MW-ish beasts, and the researchers do not say how far this effect will scale up, and in fact caution that it will not. The bits about how these might be less objectionable on aesthetic grounds don’t sway me — there’s no justification that these will look pretty to those who disapprove of regular turbines. So I’m not seeing these as “farms” and >100 m diameters would seem to exclude them as being put up in your yard.

Can I Get Insurance for it?

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Secrets of the gecko foot help robot climb

A Stanford mechanical engineer is using the biology of a gecko’s sticky foot to create a robot that climbs. In the same way the small reptile can scale a wall of slick glass, the Stickybot can climb smooth surfaces with feet modeled on the intricate design of gecko toes.

If you watch the video, you might notice that they appear to have edited out a section discussing the need for a tail — the only kept the part when they added the tail and tell us the “now stickybot can climb.” It’s too bad, because I think there’s a bit of interesting physics there. It’s mentioned briefly in this video, where you can see a real gecko with its tail pressing against a surface, the hind legs acting as a fulcrum, so that it can move its upper body back toward the surface.

"Woman Scorned" Now Available in Bottles

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Creating Hell in a Pop Bottle

You need to a flashplayer enabled browser to view this YouTube video

Some outstanding slow-motion combustion, thermodynamics, and safety advice. Half a gram of water turns into about a liter of Hydrogen + Oxygen. Then, boom!

[W]hen H2 and O2 burn, there is actually a reduction in the number of molecules of gas, which would, if all other conditions were the same actually produce a reduction in pressure, however the temperature of the exhaust gas is not the same, it goes from about 300K to 3000K which in a confined system would increase the pressure from about 1 to 10 atmospheres. This is getting close to the failure threshold of these bottles, and also represents a significant rate of release of energy.- caution is required, and this really isn’t something you should be trying unless you really know what you are doing.

Smile! Say 'Benzene Ring'

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A Better Picture of Molecules

In this type of [scanning tunneling microscope], a single hydrogen or deuterium molecule is attached to the probe tip, and the team showed that the pressure of this molecule against the probe leads to the dramatic improvement in imaging. The technique images the effect of a force on electrical conduction through the probe, which allows a more complete picture of the molecule’s electrons than standard STM provides.