Archive for March, 2014

What Happens Next Will Astound You

Top 10 Physics Findings That Will Tangle Your Brain

zapperz has already covered this; it’s got the usual hits like equating quantum teleportation and Star Trek, but the idea that the slowing of the earth means that time is slowing down is a new one. The mistake it makes is old, though; the slowing is an acceleration. 1.4 ms/day/century means that in another 100 years, all things being equal, the slowdown will be 2.8 ms/day. And that even if the rotation stabilized, if the rate were smaller then the earth would still run slow. It would just do it at a constant rate.

The one that gets me in the list is “stopped light.” The experiment is quite cool — being able to absorb light and then recreate the beam later with all of the information about its coherence and polarization intact — but “stopped light” is hyperbole.

The Uncomfy Chair

The Uncomfortable Project

I really like this, because it quite clearly shows something I’ve observed before: If it looks nice but doesn’t work, then it’s not good design.

Here Be Dragons That Rarely Interact

Physicists Produce Antineutrino Map Of The World

Physicists know that almost all of [the earth’s internal] heat is generated by the decay of radioactive elements such as potassium-40, thorium-232 and uranium-238. But how are these elements distributed and how much heat does each contribute?

In the next few years, geophysicists hope to get some detailed answers to this question thanks to the emerging science of neutrino geophysics. The radioactive decay inside the Earth produces subatomic particles known as antineutrinos. So an experiment that measures the antineutrinos coming out of the Earth should provide a detailed picture of the distribution of these elements within it.

This isn’t a map made by detection, but by calculation based on reactors. Still pretty cool.

Should You or Shouldn't You?

Should you get your PhD? (in science)

I added the parenthetical in science because I’m not sure how well the advice works well outside of it — it may have less applicability outside of physics. I have quibbles with a few things, as I’m an experimentalist and an atomic physicist, and Ethan is a theorist and is trained as an astrophysicist. There are bound to be some differences, but I think most of it is going to hold up for science PhDs in general.

There are plenty of brilliant people who get them, of course, but there are also plenty of people of average or even below-average intelligence who get them. All a PhD signifies, at the end of the day, is that you did the work necessary to earn a PhD. There are many people who have PhDs who will dispute this, of course. There are plenty of people who are insecure about their lives, too, and base their entire sense of self-worth on their academic achievements and accolades. You probably have met a few of them: they are called jerks.

This was probably the biggest surprise in grad school to me — how much the ratio of intelligence to stubbornness actually was in the student population, vs. the larger value I had naively expected it to be.

Some Old Time Fraccing

No, not fracking. Space-filling curves, which are fractal in nature.

Curves… in… spaaaace! (1890)

[S]uch a curve is quite unusual, and won’t quite look like anything encountered before. In fact, the complete curve is impossible to visualize, since it literally fills the square and, in the process, takes an infinite number of twists and turns along the way. However, we can get a feel for its behavior through an iterative process that generates curves of increasing complexity that approach the true space-filling curve in the limit of infinite iterations.

Don't Handle With Care

Antifragility and Anomaly: Why Science Works

I think I like this terminology.

Antifragility is the true opposite of fragility. Unlike mere robustness, it is the ability to actually profit from misadventure. A porcelain cup is fragile, and shatters if dropped. A plastic cup, being robust, will not be any the worse for such an experience, but it will not be any the better for it either.

Among the things that Taleb lists as fragile are scientific theories. Scientific theories are indeed vulnerable to disproof, since they must be tested against reality. The simplest way to describe this is to say that they must be falsifiable by experience, a criterion associated with the name of Karl Popper. In the popular imagination at least, however well established the theory may be from past experience, it could at any time be refuted in the future by a single observation that differs from what is theoretically predicted. If so, scientific theories would indeed be fragile, since they could not survive a single shock.

But that is not what really happens. Well-established theories have already explained a wide range of observations, and will not readily be destroyed by a single counterexample. On the contrary, they usually emerge all the stronger for accommodating to it.

Of course theories can break, but it requires contrary evidence in such a way that we can’t simply narrow the scope of the idea, i.e. the holes are in all through it rather than at an edge. Phlogiston, for example, or the early models of the atom.

By Failure, I Assume You Mean Success

Ask Ethan #29: The Most Famous Failed Science Experiment

So, then, the reasoning went, if light is a wave — albeit, as Maxwell demonstrated in the 1860s, an electromagnetic wave — it, too, must have a medium that it travels through. Although no one could measure this medium, it was given a name: the luminiferous aether.

Sounds like a silly idea now, doesn’t it? But it wasn’t a bad idea at all. In fact, it had all the hallmarks of a great scientific idea, because it not only built upon the science that had been established previously, but this idea made new predictions that were testable!

Ethan does a pretty thorough job of this, as usual, with the possible exception of not fully explaining that the observation of aberration was how scientists knew we couldn’t be at rest with respect to an aether — in their paper, Michelson and Morley specifically mention how their null result refutes Fresnel’s model of aberration (involving partial aether dragging and which was backed by an experiment carried out by Fizeau in 1851).

What I really object to here is the notion that this was somehow a failed experiment. The hypothesis failed, but it was not their hypothesis! While it’s quite likely that Michelson and Morley expected a result that was consistent with us moving through an aether, the more idealized view an experimentalist is supposed to take is to not expect a specific result at all, lest one become biased in gathering and interpreting data. That the experiment was clever and thorough enough to be able to refute an incorrect hypothesis means it was wildly successful, rather than a failure.

Trust Me, Maybe? Redux

Chad has a post up about peer-review in the context of the BICEP2 results about inflation: Review and Replication

What ultimately matters, after all is not review but replication– that is, when somebody else tries to do the same experiment, do they get the same results? This is where issues with statistical flukes usually sort themselves out, and that’s not a problem that can be fixed by any amount of refereeing. A journal referee can look for obvious gaps in the analysis, but will never get to the level of detail of a repeat experiment or a follow-up measurement.

This has some overlap with something I wrote a few weeks back (Trust Me, Maybe?) wherein I argued that peer review is a demarcation where you can start taking claims seriously, but I realize I was thinking more about theory awaiting confirmation rather than experiment. Chad’s point that there are experimental efforts where peer review will be a formality of sorts, because we already know the experiment was carefully done, is correct. What’s important here is replication.

This reminds me of a description I recently saw (but I don’t know its origin): Peer review is a spam filter. In a case like BICEP, we’re already pretty sure it’s not spam.

Not Sticking the Landing

Physics Fail in Record-Setting Car Jump Attempt

Everything seems to be fine for the first two thirds of the flight. But then the sound of the engine dies and the car starts to rock forward. Those two things are intimately connected.

This is something I noticed in the animated movie The Incredibles, where they got this part right, despite all of the suspension of disbelief required elsewhere in the movie: when the van drops free of the rocket, Mr. Incredible stomps on the gas and the van tilts back, which is at least qualitatively what you’d expect.

A Good Week for Waves Continues

‘Waves’ detected on Titan moon’s lakes

Dr Barnes, from the University of Idaho in Moscow, US, used a mathematical model to investigate whether the features in the image were compatible with waves.

“We think we’ve found the first waves outside the Earth,” he told the meeting.

“What we’re seeing seems to be consistent with waves at just a few locations in Punga Mare [with a slope] of six degrees.”

He said other possibilities, such as a wet mudflat, could not be ruled out.

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