Unit Cancellation is Weird
XKCD’s What If: Bird Droppings
Gas mileage is measured in square meters.
You can even plug it into Wolfram|Alpha, and it’ll tell you that 20 MPG is about 0.1 square millimeters (roughly the area of two pixels on a computer screen).
Unit cancellation is weird.
Superhydrophobic … Expialidocious
Operation of a flip-flop memory. After colliding with the droplet in the bistable depression in the middle, the incoming droplet lands to the other possible position in the depression in an alternating manner. Thus, the triggered output alternates between the two output channels. Real time.
Note the (mostly) elastic collision; in a head-on collision of particles of equal mass, the incoming particle comes to rest, while the target is ejected at the same speed as the oncoming particle.
A Penny For Your Thoughts.
Could a Penny Battery Power a House?
Penny batteries of the future will only take up the space of a small room and cost less than a few hundred thousand dollars.
When It Absolutely Has to Be There in Ten Minutes or Less
Relativity: Ten minutes to Alpha Centauri?
It is almost frightening how well special relativity works, and how internally consistent it is. The simple arguments presented here don’t do full justice to how smoothly the concepts of space and time are intertwined in the theory, and how much sense this link makes on close inspection. We can note, however, that the constancy of the speed of light is well-established experimentally (starting with the aforementioned Michelson-Morley experiment), and in fact time dilation has been confirmed experimentally almost countless times!
Moire Illusions, Please
'Tis the Season, 2012
What gets broadcast and where, along with an explanation of the rules for televising games.
Uncertainty About Uncertainty
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!
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
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.