The Amazing Micro-Engineered, Water-Repelling Surface That Lives Outside My Window
That’s not how water usually behaves. Water wets things. It clings to the surface and flattens out like a pancake. It doesn’t roll around like a glass bead. This leaf must have some kind of natural water-repelling surface that prevents it from getting wet.
Some slo-mo video of drops hitting a leaf at the link
Incredible art piece dances with polarized light
There’s a video in the link with the art, which is a weird combination of kinetic sculpture and optical effects from polarizers. You don’t discern the actual motion of the polarizers, but you see a motional effect from the overlap. Sort of an opto-kinetic sculpture.
One thing:
Polarizers are pieces of plastic made to only allow (or disallow) the transmission of light with certain polarizations. Natural light has a mixture of all different polarizations of light, and so any one of these polarizers only filters out a portion of the light. However, if you stack two with complementary polarizations, such as one that blocks about 50% of light and another that blocks the other 50% of light, then you end up with a totally opaque whole.
To quote a phrase: that’s not how this works! That’s not how any of this works! Simple filters don’t add linearly (they multiply — two simple 50% filters would block 75% of the light), and polarizers don’t block half each. What’s actually going on is that one polarizer sets the polarization of the light (filtering the fraction that is cross-polarized), and then the second one blocks more light, both acting according to the Law of Malus
\(I=I_0 \cos^2 \theta\)
All the light is blocked for perpendicular orientations of the polarizers, and at varying levels of light at other angles. Randomly polarized light isn’t blocked by 50% — the transmitted intensity is roughly 75%. You can see single polarizers in the video, and tell they aren’t blocked by half.
The second piece is in color but only has a still shot, so I don’t know if this is color filters or polarization with birefringent materials. I’ve posted static shots of birefringent materials before, both using a static linearly polarized source (LCD); having the background and/or foreground polarization and birefringent material move might make for an interesting display.
10 Scientific Ideas That Scientists Wish You Would Stop Misusing
From a purely physics perspective I’d include quantum on its own, because of the way it is misused: it does not mean big, it means discrete. A quantum leap can be the smallest possible leap you could make.
How Atomic Particles Helped Solve A Wine Fraud Mystery
I’ve mentioned wine fraud sleuthing before, and this is another telling of one of those stories. If interested, it’s probably worth reading Jennifer Ouellette’s post and her included link to the New Yorker article, for full coverage of the details.
Choprafication: The act of adding of “quantum” to a description to make it sound all science-y and stuff
– Me (no relation)
Quantum and Consciousness Often Mean Nonsense
I hold degrees in physics and have spent a lot of time learning and teaching quantum mechanics. Nonphysicists seem to have the impression that quantum physics is really esoteric, with those who study it spending their time debating the nature of reality. In truth, most of a quantum mechanics class is lots and lots of math, in the service of using a particle’s quantum state—the bundle of physical properties such as position, energy, spin, and the like—to describe the outcomes of experiments. Sure, there’s some weird stuff and it’s fun to talk about, but quantum mechanics is aimed at being practical (ideally, at least).
Yet the mysterious aspects of quantum physics and consciousness have inspired many people to speculate freely. The worst offenders will even say that because we don’t fully understand either field, they must be related problems. It sounds good at first: We don’t know exactly how some things in quantum physics work, we don’t know exactly how to go from the brain to consciousness, so maybe consciousness is quantum.
The problem with this idea? It’s almost certainly wrong.
New Paper
Evaluation of long term performance of continuously running atomic fountains. Metrologia 51 263-269
An ensemble of rubidium atomic fountain clocks has been put into operation at the US Naval Observatory (USNO). These fountains are used as continuous clocks in the manner of commercial caesium beams and hydrogen masers for the purpose of improved timing applications. Four fountains have been in operation for more than two years and are included in the ensemble used to generate the USNO master clock. Individual fountain performance is characterized by a white-frequency noise level below 2 × 10^−13 and fractional-frequency stability routinely reaching the low 10^−16 s. The highest performing pair of fountains exhibits stability consistent with each fountain integrating as white frequency noise, with Allan deviation surpassing 6 × 10^−17 at 10^7 s, and with no relative drift between the fountains at the level of 7.5 × 10^−19/day. As an ensemble, the fountains generate a timescale with white-frequency noise level of 1 × 10^−13 and long-term frequency stability consistent with zero drift relative to the world’s primary standards at 1 × 10^−18/day. The rubidium fountains are reported to the BIPM as continuously running clocks, as opposed to secondary standards, the only cold-atom clocks so reported. Here we further characterize the performance of the individual fountains and the ensemble during the first two years in an operational environment, presenting the first look at long-term continuous behavior of fountain clocks.
I bolded something I harp on occasionally: these clocks are actually run as, and are reported as, clocks. For all of the awesome performance of other devices that grab pop-sci article space, they don’t run continuously and aren’t described as clocks when it comes to the data that get reported to the international standards lab.
This perpetual motion machine she made today is a joke! It just keeps going faster and faster.
…
Lisa! Get in here. In this house, we obey the laws of thermodynamics! – Homer J Simpson
Perpetual Motion Email Guidelines
Short version: no, it won’t work.
“If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.”
— Arthur Eddington, The Nature of the Physical World (1928)
A Supertask Shows How Particles Can Spontaneously Start Moving
A particle, traveling at a meter per second, knocks into the square. Because the particle’s speed is a meter per second, and the square is a meter wide, within a second, all the motion that was introduced into the square is gone. But there is no particle ejected. The infinite amount of collisions means there is no final particle. The motion just stops.
The problem with thought experiments is that if they lack rigor, it’s easy to argue into something that is contrary to the laws of physics. With a verbal description, you can get something like Zeno’s paradox, which seems like a contradiction until mathematical rigor is applied.
I think the above is such an example. Somebody has taken a liberty with infinities or made a hand-wavy argument somewhere in the middle of all this. The conclusion violates conservation of momentum and energy, so there’s a flaw somewhere. I’d like to hear more about how the motion ceases after one second. There’s a dodgy assumption in there, I’m sure. There may be an infinite number of particles but they are also infinitely small, so how do you determine their cross-section and the resulting collision rate?
The paper isn’t even that subtle.
What happens at t = 1? By that time, every particle Pi has collided with its immediate left-hand neighbor and so is stationary. Therefore, all the particles are stationary.
Um, what? At that point I confess I stopped reading. This sounds like a technicality of math that doesn’t apply to a real system, i.e. there is no “last particle” that’s moving. If you assume something that is physically impossible, you can come to just about any conclusion you want.
Quantum positioning system steps in when GPS fails
The mention that this is based on laser-cooled atoms, with no further details, is a tad frustrating. In grad school I worked on a laser-cooled atom interferometer, which could be used as an inertial sensor. In principle, at least, since the device I worked on was relatively big; the vacuum system was an “L” that was at about a meter in the short dimension and there was a large optical table to generate the laser light. There is more than one way to build such a device, though, and these processes can be made much smaller with engineering effort, so the lack of detail is disappointing.
Millikan, Einstein, and Planck: The Experiment io9 Forgot
I object to the [io9] headline for reasons beyond the cheap sensationalism– it’s also overlooks half of the citation for Millikan’s 1923 Nobel Prize in Physics:
for his work on the elementary charge of electricity and on the photoelectric effect
An important note that Millikan’s prize was not just for the oil drop experiment, and I am in agreement that this analysis (pdf) does a convincing job in debunking this old Millikan-fudged-his-data idea.