Survivor Skills

This may prove useful in in the event you absolutely must open a bottle of wine but have no corkscrew.

How to open a wine bottle with a shoe.

Technically a shoe and a wall. My French is pretty much limited* to Je ne parle pas Français (and croissant, so I would never say Je ne parle pas croissant) so I assume the narrator is telling you that pressure is force/area, and so any force you exert on the liquid at the base by whacking the bottom of the bottle will result in a much larger force being transmitted to the cork owing to the reduction in area.

What he is probably not telling you is that this is a poor technique for ketchup, and not because French cuisine and ketchup are incompatible or that it won’t work on screw tops (both true) but that ketchup is a non-Newtonian fluid, and when the ketchup clogs the neck of the bottle it prevents air from entering, which is necessary to let the ketchup flow. Don’t invert and bang on the bottom (this holds true for more than ketchup, but I digress). Hold it with the open end down at 45º and tap the neck to induce the shear-thinning.

(*My limited vocabulary also allows me to get the following joke: Why do French omelettes have only one egg? Because in France one egg is un oeuf.)

Violating the Violation

Cosmic Variance: Marketing CP Violation

Sean discusses the recent CP violation results, and how they were reported.

The point is that the conclusion doesn’t hold — not everything about CP violation is necessarily related to baryogenesis. We don’t know how baryogenesis actually happened — there are many theories on the market, and any of them or none of them may be right. Therefore, there’s no way of knowing whether any particular manifestation of CP violation is in any way related to baryogenesis. There could be lots of different ways in which CP is violated. In particular, there’s no compelling theoretical reason why the CP violation being studied in the decays of B mesons has anything at all to do with baryogenesis. It’s possible — lots of things are possible. But what’s being studied isn’t baryogenesis; it’s CP violation.

Mea culpa. Ten 3-loop Feynman diagrams as penance.

Don't Drop any Mentos in it

The Strangest Disaster of the 20th Century.

A recounting of the Lake Nyos CO2 eruption in Camaroon.

There is a physical limit to how much CO2 water can absorb, even under the tremendous pressured that exist at the bottom of a 690 foot deep lake. As the bottom layers become saturated, the CO2 is pushed up to where the pressure is low enough for it to start coming out of solution. At this point any little disturbance—a landslide, stormy weather, or even high winds or just a cold snap—can cause the CO2 to begin bubbling to the surface. And when the bubbles start rising, they can cause a siphoning or “chimney” effect, triggering a chain reaction that in one giant upheaval can cause the lake to disgorge CO2 that has been accumulating in the lake for decades.

Mock 1

Which is, of course, the speed of sarcasm

Can you guess which is the real article title? arXiv vs snarXive

I converged to 63% after 30 guesses

The snarXiv is a random high-energy theory paper genera­tor incorporating all the latest trends, entropic reasoning, and exciting moduli spaces. The arXiv is similar, but occa­sionally less random.

via the holy one

Next Up, the Behemyth

I think a larger version of this should be called the Leviatron

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Neat, even with the overindulgence of “let’s enclose this in a tube to prove there are no wires.” Two things, though. 1) It’s not antigravity 2) The blurb about torque isn’t right — it’s not that the spinning exerts a torque, it’s that the spinning means there is angular momentum. You need a torque to change angular momentum, and the torque present because of the same-facing poles is not enough to flip the top. Just like gravity exerts a torque, but cannot flip the spinning top, either.

Drinking My Vodka and Lime

Uncertain Principles: Relativity on a Human Scale

Precision clock measurements from NIST, directly observing both gravitational and kinematic time dilation, all without leaving the lab.

You can do this type of experiment with less precise devices, but you’d have to have a more robust apparatus to accumulate the data because you’d need to do a longer experiment. I’ve detailed how commercially available clocks have done the kinematic dilation measurement, though at ~30 m/s rather than 10 m/s, which required an experiment lasting several days. Similarly, one could do an experiment with clocks on different floors of a building over the course of a few weeks and see a gravitational redshift. It’s probably not worth the effort to go out of your way to do so, given the level of confirmation we already have for relativity — GPS works, for example.

The trick here is that these measurements were made in a relatively short period of time, but that’s generally the nature of cutting-edge science like this — it takes a lot of effort to get all the parts to run, and the experiment yields data for a limited time. So Chad is correct in asking whether they really count as “official clocks” — they don’t insofar as timekeeping is concerned. They probably don’t run long enough to really impact a true clock ensemble. The value here is that what’s hard to do today will be easier to do tomorrow, and eventually this (or a competing) kind of technology will become “true” clocks that are more compact and run continuously for extended periods and do have a significant impact on timekeeping.

(I should be listening to similarly-themed talks this week — I was supposed to go the Frequency Control Symposium. But I managed to get sick — not vodka-induced, BTW — as the weekend drew to a close. No way I was getting on a plane at that point. Bleh.)

If it Disagrees with Experiment, it's Wrong

Feynman sums up science

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What he doesn’t explain here, however, is that there are varying degrees of wrong. Some kinds of wrong mean you abandon the theory. Other kinds of wrong mean you adjust the theory. Once can look at the scrap heap of discarded theories for examples of the former — phlogiston, for example, predicted that mass had to decrease in the process of combustion, because it was a substance released during the process. After that was shown to be wrong, the theory was discarded. There was no way to fix the problems, since it wasn’t a matter of refinement.

An example of refining a theory is found in laser cooling. When it was first proposed, the mechanism was Doppler cooling, stemming from a simple model of photon recoil in a two-level system, and was experimentally confirmed. But eventually experimenters discovered conditions where their laser-cooled atoms were colder than the Doppler limit. Atoms are not two-level systems, and there are conditions in which their structure can be exploited to cool the atoms further: polarization gradients in the laser light, giving rise to “Sisyphus” cooling, in which the energy levels of the atoms are shifted depending on their position, and it is possible to have some atoms continuing to lose energy as they scatter photons, somewhat like the mythological Sisyphus, who was cursed to continually push a rock uphill. It was this discovery and explanation that won the 1997 Nobel prize for Bill Phillips, Steven Chu and Claude Cohen-Tannoudji.

There are more of these examples, with the hallmark being that the original theory is seen to no longer have universal applicability, but is still used under the conditions in which it applies. Relativity comes immediately to mind; we still use Newton’s law of gravitation, still use the classical equations for e.g. kinetic energy and do Galilean transforms when using them doesn’t introduce appreciable error.

We're All Idiots, or Worse

Over at Physics and Physicists, I saw the post entitled Graduation Speaker Perpetuates Myth, in which the old “science says bumblebees can’t fly” canard is reported, yet again. What gets me is about such stores is the willingness to accept that scientists are imbeciles — embracing the idea that we would advance models as truth, despite the fact that they are so trivially falsified. In science, if the theory does not match the experiment, you know something is wrong with the theory, so you change the theory. (in this case, a combination of the assumption about the rigidity of the wing and the nascent state of aerodynamic modeling limited a back-of-the-envelope calculation at a dinner party)

Worse, in addition to (or perhaps a subset of) the willfully ignorant, we have the conspiracy theorists. Not only is the science wrong, but we’re all actively covering up the flaws. Never mind that if any technology based on the science actually works, it’s a bit troublesome for their position. My favorite is the anti-relativity crowd scrambling to explain how GPS actually can work.

In light of that, it was interesting to read about what has been termed scientific impotence: When science clashes with beliefs? Make science impotent

What Munro examines here is an alternative approach: the decision that, regardless of the methodological details, a topic is just not accessible to scientific analysis. This approach also has a prominent place among those who disregard scientific information, ranging from the very narrow—people who argue that the climate is simply too complicated to understand—to the extremely broad, such as those among the creationist movement who argue that the only valid science takes place in the controlled environs of a lab, and thereby dismiss not only evolution, but geology, astronomy, etc.

So now we have the addition of science isn’t equipped to answer that question.

Lather and Rinse

Tell and Repeat courses

Aka student regurgitation. To avoid this, one must come up with questions which test for understanding, rather than information chucking in the vertical direction.

Anyway, Rhett mentions a wonderful conceptual question, and one I had not run across before, as an example.

The only bad thing about this question is that they aren’t trivial to create. Oh snap – well, I just gave away an awesome question. Truthfully, this question has been “out in the wild” for a long time. It is still a great question and you could probably use it on a test. The problem with a question being in the wild is that students can just memorize the solution – this means that question no longer tests for understanding.

One solution is to have a large number of questions, so that simple memorization is difficult, but these questions are hard to come by. Another is to have modular questions, so that you could ask about the same concept in different ways, but that’s far easier with algebraic results, where you change what information is given and which variable you want the students to solve for. I’m not sure to what extent it’s possible with a discussion question. Rhett’s example changes a variable, certainly, but not in the same way as an algebraic problem.

Another, I think, is to phrase a situation with a contradiction and have the students find out what the problem is with the phrasing of the question — a “why isn’t this possible?” kind of problem, or “find the fish flaw.” I see this all the time in crackpot discussions; once you remove the rigor of math, it’s easy to state a model which has some unphysical aspect and contradicts itself, which is why thought experiments alone can never disprove some phenomenon, and why perpetual motion machines are easy to describe but never work.

Here’s a classical physics example: you swing a bucket in a big circle which passes over your head. You adjust the speed so that the bucket comes to stop, with the string taut, directly overhead, at which point the bucket and water fall on your head. Is that possible?

A student may think so, because from a conservation of energy standpoint all you need is to have the kinetic energy at the bottom be equal to the potential energy at the top, so that the kinetic energy vanishes, and presto! You’re wet. But this ignores the requirement of the taut string: in order for that to be true, there must circular motion (not uniform, because v will be changing, but still circular) and this requires that there be tangential movement. Even as the tension tends toward zero, there is still gravity, so at the apex you would still have a centripetal acceleration, and thus v cannot go to zero. The bucket cannot come to a stop directly overhead with a taut string. (and yet it was so easy to state that it would happen …)