Category Archives: Physics

George Will is a Boulder

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Global warming advocates ignore the boulders

He’s certainly not a scientist, nor, seemingly, is he scientifically literate.

In his latest steaming pile of op-ed on global warming, Mr. Will attempts to call into question the “settled science” of global warming by discussing virtually no science at all. Seriously — a bunch of politicians not being able to agree on a course of action does nothing to question the science. And likewise for businesses making a business decision. But it is the claim that there has been no recent warming that is what really bugs me. George almost gets it right earlier in the op-ed, when he says there has been no statistically significant warming in the last 15 years, but here he (and many others) sin by omission. If one follows the link back to the BBC interview with Phil Jones, one gets a better picture

Do you agree that from 1995 to the present there has been no statistically-significant global warming

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

In other words, if one has a sufficiently noisy data set, it is always going to be possible to pick a subset of the data where the noise masks any statistically significant trend. It doesn’t mean the trend isn’t there, or that the best fit is a zero slope. When Jones says “Yes, but only just” he’s telling us that one can just draw a flat line through the data, but this means that one could also draw a line with a slope of 0.24C per decade through the data, and it would have the same importance — you can’t exclude warming at that rate, either.

Imagine this question being asked instead:

Do you agree that from 1995 to the present it’s possible there has been global warming at a rate as high as 0.24C/decade?

The answer would have to be essentially identical, i.e. it would have to be yes. You can only statistically exclude warming at a higher rate than that!

What one certainly can’t do (that is, with any intellectual honesty) is conclude that this is an absence of warming. Statistically speaking, if the best fit to the data were a line with no slope, one could rule out neither an increase nor a decrease — one could only quote a limit on those trends. That’s one of the things about science — we try and quantify our results, rather than bandy about generalities. You might force a sound-bite answer out of a scientist (or worse, get there by ripping a quote out of context), but the instinct is to properly qualify the result.

So what if you don’t want both of the above scenarios to fit Dr. Jones’ answer? If you want a statistically significant answer you have to do as he suggests and look at a longer set of data in order to beat the noise down (random noise will average out with the square root of the number of data points). Anyone who does experimental science knows this, and is one of those things that a scientifically literate person should know. So the choice of a short data set is a form of cherry-picking — selecting a data set in such a way as to present a misleading result. If one looks at a longer data set, a statistically significant trend does emerge, and it is one of warming.

George, you’re not a scientist. I had some respect for you in the days I used to read your opinion pieces, because you could and did make cogent arguments, even if I did not agree with you. But science is based on facts, not opinions, and when you have to misrepresent those facts to make your point, your conclusions aren’t worth the paper on which they are printed.

Update: there’s more

Sun Dog Beat Down

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Atlas V launch earlier this month. The rocket goes supersonic as it passes through the cloud layer that was prettily refracting light from the sun (a sun dog), with the shock wave visible in the clouds and disrupting the effect. The fun starts at about 1:50, and is replayed a few times after that.

You need to a flashplayer enabled browser to view this YouTube video

Feel the Burn, Baby

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Pictured: Incredible gravity-defying ant that can carry 100 times its body weight

The photo shows an Asian weaver ant hanging upside down on a glass-like surface and holding a 500mg weight in its jaws. It was captured by Dr Thomas Endlein of Zoology department at the University of Cambridge who was investigating the sticky feet of ants and other insects.

No mention of results of any steroids testing on the ant.

Hair Care at the Olympics

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Not that I need any help in that area.

I’ve been watching the curling televised in the afternoons this past week, and I have to apologize to the US teams — as soon as I tuned in, you tanked. Choked. Collapsed. Obviously, I’m bad luck and it’s all my fault. But I still enjoy watching; I was first exposed to the sport when I lived in Canada (though I knew people who curled when I was growing up; there was/is a curling rink right in the middle of Niskayuna)

Ran across this set of animations. The Physics of Curling

And obviously, you need to analyze the sweeping, too.

The claim is that the sweeping warms, but does not melt, the ice. However, there’s always some liquid on the surface, and temperature measurements don’t tell you everything, because pressure matters, too. But take all of that video with a grain of salt, because

Jenkyn’s full results are being kept secret until June 2010, revealed only to Canada’s Olympic athletes, coaches and officials.

“We’re sworn to secrecy,” he said.

It could all be a smokescreen to sabotage other teams. Maybe I’m off the hook.

Update: The men won last night. It’s not me.

See the Music

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Record grooves under an electron microscope

It has CD pips, too, for those of you too young to remember what a “record” is.

But if you put a needle in the groove and moved them relative to each other, the needle would wiggle back and forth. Use a transducer to convert it to an electrical signal, amplify it and send it to a speaker (which would essentially do the reverse). The groove is a composite of all the waveforms of the song, added together.

Mr. Smith Doesn't Go to Utah

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13-year-old helps save daylight saving in Utah

I know this is supposed to be an uplifting story of how clever a teenager is, in a sort of afterschool special kinda way, but I’m more cynical than that. I see it as a bunch of blowhard politicians happily debating something they do not understand, have made no effort to understand, but are willing to make a decision about anyway, despite the fact that by not understanding the issue you have no hope of recognizing the ramifications of your decision. All this despite the fact that a teenager can understand and explain the concept, so it really wouldn’t have been all that difficult to have a staffer spend a few minutes Googling the information and summarizing it for you.

Einstein Passes, Again

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Most precise test yet of Einstein’s gravitational redshift

When the cesium atom matter wave enters the experiment, it encounters a carefully tuned flash of laser light. The laws of quantum mechanics step in, and each cesium atom enters two alternate realities, Müller said. In one, the laser has pushed the atom up one-tenth of a millimeter – 4/1000 of an inch – giving it a tiny boost out of Earth’s gravitational field. In the other, the atom remains unmoved inside Earth’s gravitational well, where time flies by less quickly.

While the frequency of cesium matter waves is too high to measure, Müller and his colleagues used the interference between the cesium matter waves in the alternate realities to measure the resulting difference between their oscillations, and thus the redshift.

This is the UC Berkeley press release, and if one can ignore the use of the “many worlds” reference of alternate realities, is otherwise pretty good. It also includes some laser table porn which has been filtered out of the other stories I’ve run across. I’ve only had a chance to glance at the article, but there’s a lot of interesting physics in there that is not mentioned in the press release, or in the Nature summary story that ran in addition to the article (and was somewhat disappointing in terms of how it recapped the experiment).

The basic experiment is a decade old; the original idea was to measure the local value of g, because the two paths of the atoms have an energy difference of PE = mgh, and that gives you a phase difference for the two paths. The trick here is in reinterpreting the results in terms of relativity. I’ll try and summarize the details soon.

Stop! In the Name of Physics

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In Brookhaven Collider, Scientists Briefly Break a Law of Nature

The departure from normal physics manifested itself in the apparent ability of the briefly freed quarks to tell right from left. That breaks one of the fundamental laws of nature, known as parity, which requires that the laws of physics remain unchanged if we view nature in a mirror.

Ok, that’s interesting — that the reaction violated parity conservation, which I imagine has implications for the matter/antimatter asymmetry issue (I have long wondered if symmetry violation conditions changed with energy, and now it appears that they can and do). But if a reaction violates parity conservation, then parity conservation is not a law of nature; at best you have a “parity conservation zone.” Laws of nature describe how nature behaves. Whatever nature does, it is in accordance with these laws.

The editor who came up with the title needs to write “It is impossible to violate the laws of nature” a thousand times.

For more on the science, and confirmation that this follows, rather than breaks, the laws of physics, check out Cosmic Variance

Update: for some backstory on parity violation, check out Symmetry: It’s More Like a Guideline about the confirmation of how weak interactions don’t “keep to the code.”

Don't Sign Them, Though

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Let’s draw Feynman diagams!

So we see that the external lines correspond to incoming or outgoing particles. What about the internal lines? These represent virtual particles that are never directly observed. They are created quantum mechanically and disappear quantum mechanically, serving only the purpose of allowing a given set of interactions to occur to allow the incoming particles to turn into the outgoing particles. We’ll have a lot to say about these guys in future posts.

Great Jumping Sand Grains, Batman!

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Martian Dune Mystery Solved by Bouncing Sand Grains

The way sand grains knock each other around turns out to make all the difference, Kok says. Because Martian gravity and air density are so much lower than Earth’s, a small kick from the wind sends sand particles on Mars flying much higher, up to a meter off the ground.

“It’s like playing golf on the moon,” Kok says. Particles get caught in stronger winds as they rise, causing them to pick up speed and ultimately slam into the ground, where they kick up more particles and start the cycle over. “This splashing process is really efficient,” Kok says. “It can keep saltation, or sand blowing, going on Mars at relatively low wind speeds.” These jumping sand grains can create ripples over time even without high sustained winds, he says.