Monthly Archives: September 2012

Uncertainty About Uncertainty

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University of Toronto scientists cast doubt on renowned uncertainty principle

Oh, my. That would be interesting indeed.

Werner Heisenberg’s uncertainty principle, formulated by the theoretical physicist in 1927, is one of the cornerstones of quantum mechanics. In its most familiar form, it says that it is impossible to measure anything without disturbing it. For instance, any attempt to measure a particle’s position must randomly change its speed.

However, this isn’t the Uncertainty Principle, it’s the observer effect. To be fair, this was the original argument that Heisenberg put forth back in the early days of QM, but not what it became: that you cannot simultaneously determine the position and momentum. It’s problematic that the observer effect description is still taught when introducing the HUP (much like the problems introduced by teaching the Bohr model).

The APS summary does a much better job.

When first taking quantum mechanics courses, students learn about Heisenberg’s uncertainty principle, which is often presented as a statement about the intrinsic uncertainty that a quantum system must possess. Yet Heisenberg originally formulated his principle in terms of the “observer effect”: a relationship between the precision of a measurement and the disturbance it creates, as when a photon measures an electron’s position. Although the former version is rigorously proven, the latter is less general and—as recently shown—mathematically incorrect. In a paper in Physical Review Letters, Lee Rozema and colleagues at the University of Toronto, Canada, experimentally demonstrate that a measurement can in fact violate Heisenberg’s original precision-disturbance relationship.

Look, Ma! No Diffraction!

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Plasmon Wave Propagates for 80 µm with No Diffraction

The cosine-Gauss plasmon beam, caused by quasiparticles called surface plasmons, remains very narrow and controlled along an unprecedented distance, said a Harvard University-led American and French team. The surface plasmons travel in tight confinement with a nanostructured metal surface. The metallic stripes that carry these plasmons have the potential to replace standard copper electrical interconnects in microprocessors, enabling ultrafast on-chip communications.

Four Legs Good, Two Legs Bad

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DARPA’s Cheetah robot—already the fastest legged robot in history—just broke its own land speed record of 18 miles per hour (mph). In the process, Cheetah also surpassed another very fast mover: Usain Bolt. According to the International Association of Athletics Federations, Bolt set the world speed record for a human in 2009 when he reached a peak speed of 27.78 mph for a 20-meter split during the 100-meter sprint. Cheetah was recently clocked at 28.3 mph for a 20-meter split. The Cheetah had a slight advantage over Bolt as it ran on a treadmill, the equivalent of a 28.3 mph tail wind, but most of the power Cheetah used was to swing its legs fast enough, not to propel itself forward.

I have to point out that Usain Bolt does not have a tether attached to him to protect himself from falls if he tries to run too fast, which is another advantage for the robot.

Google Earth Fractals

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Google Earth fractals

The following is a “photographic” gallery of fractals patterns found while exploring the planet with Google Earth. Each is provided with a KMZ file so the reader can explore the region for themselves. Readers are encouraged to submit their own KMZ files for inclusion, credits will be included.

The World's Thinnest Trampoline

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Super-stretchy jelly can take a hit

Suo’s hydrogel is made from a mixture of two polymers — alginate and polyacrylamide. Each polymer forms networks using different types of chemical bond: alginate molecules are linked together by ionic bonds, and polyacrylamide molecules by stronger covalent bonds. When the gel is stretched, hit or torn, the ionic bonds can break and reform throughout the material, dissipating energy over a wide area and causing fewer of the covalent bonds to be irreversibly ruptured. The covalent bonds hold the material together, allowing it to spring back to its original shape.

Let's Drink Beer. For Science!

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Glass Shape Influences Consumption Rate for Alcoholic Beverages

Participants were 60% slower to consume an alcoholic beverage from a straight glass compared to a curved glass. This effect was only observed for a full glass and not a half-full glass, and was not observed for a non-alcoholic beverage. Participants also misjudged the half-way point of a curved glass to a greater degree than that of a straight glass, and there was a trend towards a positive association between the degree of error and total drinking time.

Wait, degree of error increased with total drinking time? Nooooooooooo!

The Modern Soylent Green: The People are the Product

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By now we’re pretty used to being the product, as many of us participate in online activities like Facebook or Twitter, and/or photo-sharing sites, where we provide the content. (On some of those sites, what we post actually becomes the property of the host. Read carefully!) Here’s another example of being the product:

Award-winning footstep energy to help power shopping centre
and
Pavegen. Renewable energy from footsteps.

Each tile has a capacity of 6 watts, but in order to use the tile’s full capacity, there needs to be a constant flow of about 50 steps / minute.

The reality is that the tiles are seeing about 5 steps / minute, and on a good day, the kinetic sidewalk will generate about 75 watt-hours of electricity. This is equivalent to powering an old 60-watt incandescent lightbulb for about 1 hour and 15 minutes.

Let’s start with the obvious: one could take the view that this is stealing. Someone is taking work you (the actual physics definition of work, at that) and using it without paying you. It’s also being advertised as being green and self-sustainable. It also needs to be cost-effective. Is it?

Let’s run the numbers. The pad flexes ~5mm when you step on it, so that’s about 5 Joules of work for a mass of 100 kg, so that’s roughly in agreement with the 50 steps/min giving 6 Watts, assuming high efficiency. 75 W-h is 270 kJ of energy. At an electricity rate of $0.12 per kWh, this represents a penny of electricity.

A penny.

The device has to be less than 100% efficient and your body’s conversion of food into the energy being harvested certainly isn’t (I’ll assume around 25%), so at 4.18 kJ per Calorie, the people providing this energy collectively burned about 270 Calories, which came from the food they ate. The cost of that food can vary widely, but it’s going to be on order of a dollar, making this system’s cost efficiency about 1%. (This won’t change at higher power production, either) And here’s where (and why) the claims of “green energy” fall apart. Touting human power as green is dubious, because you don’t know where the food came from, but odds are it’s not all that “green”, and to tout this as a replacement — at 1% efficiency — means that the people providing the energy need to have 1/100 of the carbon footprint of the raw electricity. Transporting the food, preparing it, etc. has to be greener than the energy it replaces by a factor of 100, and there’s no way it is. This is a misdirection, moving the carbon footprint issue out of immediate sight, asking us to pay no attention to the carbon footprint behind the curtain. Human power is not green — the only time it works is if you are harnessing energy that would otherwise be wasted, similar to regenerative braking on electric cars.

Is it cost-effective? I couldn’t find a credible price anywhere, save for a promised target of $50 per tile once production ramps up. Installation is probably the largest cost, along with some infrastructure of wiring, batteries and an inverter. At the target traffic load giving an output of 6 Watts, even if the traffic were present all day long, that’s 1 kWh per week per tile. At $0.12 per kWh saved, that’s just barely $6 a year in electricity savings. The tiles were installed at a tube station at the Olympics and generated just 20 kWh from 12 tiles. The olympics ran 16 days (the story says two weeks); it’s ballpark agreement either way. 20 kWh is $2.40 of electricity.

Unless I’m missing something, there’s no way this is cost-effective. You can pay for it out of your advertising budget, raising awareness of, well, something, since it’s not green, which means it’s just a gimmick.