There’s nothing physically blocking the atoms from flying right through the channel– in fact, an atom that enters the channel will always exit the other side without slowing down along the way. This is termed “ballistic,” a term that will always have a special place in my heart thanks to an incident at my Ph.D. defense.
Category Archives: Physics
After This We Hypnotize the Drops
Acoustic Levitation of Liquids Looks Like Magic
No magic show: Real-world levitation to inspire better pharmaceuticals
The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range – roughly 22 kilohertz. When the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave.
The speed of sound is about 340 m/s, so a 22 kHz wave has a wavelength of about 1.5 cm; the nodes would thus be half that distance apart, but you wouldn’t have to fill every node. Notice the effect at 0:30, where the standing wave is adjusted — you can see the drops move up and down, in tandem.
This seems to be analogous to a dipole force trap in atomic physics. If that’s so, you’d have a radial pressure gradient also giving confinement, which might account for the somewhat strange look to the speakers.
How Does it Do in the Rain?
This $9 Cardboard Bike Can Support Riders Up To 485lbs
Engineers told Gafni that his idea was impossible. Yet he realized that paper could be strong if treated properly. As in crafting origami and tearing telephone books, he explains, “[if] you fold it once, and it’s not just twice the strength, it’s three times the strength.”
The Trouble with TBBTles
The Problem With The Big Bang Theory…
When Big Bang came along it claimed to be heralding a new age of “geek chic”, nerd culture was cool and mainstream television wanted a piece of the pie (or should that be pi?). Here was a programme whose main ensemble was made up of four highly intelligent scientists who love science fiction, fantasy and gaming. Here was a show with nerd protagonists aimed at the mainstream. We were finally getting some representation.
Except that we’re not. At least not any more.
And here’s my issue, here’s why The Big Bang Theory makes me feel uncomfortable. We aren’t laughing with Leonard, Sheldon, Raj and Howard. We’re laughing at them. Chuck Lorre has given us four exceptionally intelligent, nerdy main characters and he’s positioned us as an audience against them. When I watch Big Bang it becomes more and more obvious that I’m not supposed to relate to the guys (or more recently Amy Farrah-Fowler). I’m expected to relate to Penny. You only need to pay attention to the audience laughter to realise that TBBT relies on positioning us as an outsider to the nerds, as someone like Penny who doesn’t understand their references, their science, their vocabulary even, and who doesn’t care to learn.
I’ve only seen parts of of few episode, so my own analysis could not go this far; to me the show is unwatchable.
Wrong Heisenberg is Wrong!
Another article on the Heisenberg experiment I linked to earlier
Common Interpretation of Heisenberg’s Uncertainty Principle Is Proved False
However, I think that the author is not quite getting it
The uncertainty principle limits what we can know about a quantum system, and that fuzziness is not entirely caused by the act of measurement.
No! The Heisenberg uncertainty is not at all caused by the measurement! That’s a separate phenomenon that can add to the total uncertainty you have. The thing is, the Heisenberg Uncertainty Principle doesn’t require uncertainty of any one parameter, it limits the accuracy of simultaneous measurements of certain parameters.
The critique of incorrectly teaching the observer effect as the HUP in intro classes is quite correct, though.
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!
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.