Category Archives: Physics

The Toe of God

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A New Clue to Explain Existence

More data concerning the matter/antimatter abundance conundrum.

Sifting data from collisions of protons and antiprotons at Fermilab’s Tevatron, which until last winter was the most powerful particle accelerator in the world, the team, known as the DZero collaboration, found that the fireballs produced pairs of the particles known as muons, which are sort of fat electrons, slightly more often than they produced pairs of anti-muons. So the miniature universe inside the accelerator went from being neutral to being about 1 percent more matter than antimatter.

Doing Nothing?

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There’s a management phenomenon, which is magnified by politics: if some unusual circumstance occurs, doing nothing is usually deemed worse than doing the wrong thing. There’s usually no easy way to quantify the nothing that you did, even if you actually investigated carefully. There’s the though that “we have to do something!” and even if the action is inappropriate or ineffective, management can point to it and say, “See! We did something about it.” (I think our current terrorism responses too often fall into this category.)

I was reminded of that lesson when I read this story: Tainted nuke plant water reaches major NJ aquifer

The tritium leaked from underground pipes at the plant on April 9, 2009, and has been slowly spreading underground at 1 to 3 feet a day. At the current rate, it would be 14 or 15 years before the tainted water reaches the nearest private or commercial drinking water wells about two miles away.

But the mere fact that the radioactive water – at concentrations 50 times higher than those allowed by law – has reached southern New Jersey’s main source of drinking water calls for urgent action, Martin said.

Now, it’s possible that what is being reported isn’t the whole story, and there is legitimate cause for concern. But based on what was in the story, I think the call for urgent action is based on the sphincter-clenching response the general public has to the word “radiation.” Let’s look at the details.

— The half-life of Tritium is 12.33 years. Which means that less than half will be left when it reaches the drinking water. 50x becomes <25x

— If the diffusion is isotropic, and only in the radial direction, the Tritium will be diluted by another factor of 14 or 15. 25x becomes less than 2x.

— Diffusion rates depend on the gradient of the concentration. As the Tritium becomes diluted, the diffusion should slow down. It's not clear that the estimates take this into account. The story gives the current rate as 1-3 feet per day. 2 feet per day is 2 miles in 15 years.

— Tritium is delicious and wholesome

So, based on the information given, it's possible the tritium concentration will be at or below the legal limit by the time it enters the drinking water (which could dilute it even more). The person calling for urgent action works for New Jersey's environmental protection department, so one would hope that the science was considered. But I suspect that "urgent action is required" is the response because trying to assuage peoples' fears would be viewed as a smokescreen, and simply levying a fine (which I'm all for — the power plant should not be let off the hook) might be taken as the company buying their way out of the problem.

Bohm, Bohm, Bohm-Bohm

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(Try the title with the Dragnet theme in mind, if you’re old enough.)

The aforelinked Bohemian Mechanical Rhapsody was fallout from some discussion on quantum mechanics interpretations, namely Quick Impressions of Bohmian Mechanics and The Problem of (Quantum) Moderation: On Many Worlds

QM interpretations is a subject that can go into quite amount of detail and some people are quite passionate about it, as some of the comments in those threads show. Alas, I just don’t find myself getting worked up enough to tackle any of it in any real depth. I don’t see that there is ultimately any result that shows one interpretation to be any better in an objective sense, which makes it metaphysics. All of it seems to be ways of casting quantum mechanics in some more comfortable classical (or at least quasi-classical) framework, which I think only serves to deny that quantum mechanics really is weird. If that helps you understand it, great, but don’t lose sight of the fact that science is a description of how nature behaves, not how it really is. It’s only a model, and if you don’t want to go to quantumland because it is a silly place, then pick up one of the interpretations.

Update: The discussion to which Ian referred: Is the wavefunction ontological? (which I did read, honest, and should have thought to include)

Why I Am Majoring in Physics

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funny graphs and charts
see more Funny Graphs

The green option was not available before 1977, of course. Not sure what all of the alternatives were then, but mine was partly that I wanted to be Barney from Mission: Impossible. (The TV show, which had no association whatsoever with Tom Cruise)

The Dictionary is not a Technical Resource

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QUT physicist corrects Oxford English Dictionary

Dr Hughes said the Oxford English Dictionary (OED) since 1911 had incorrectly stated that atmospheric pressure was the operating force in a siphon when in fact it was gravity.

“It is gravity that moves the fluid in a siphon, with the water in the longer downward arm pulling the water up the shorter arm,” he said.
Now the illustrious Oxford English Dictionary’s editors are moving to have the definition corrected, after receiving an email from Dr Hughes.

Atmospheric pressure is actually smaller at the short end of the siphon, so it should be obvious that pressure is not the main effect. When the liquid in the long arm drops due to gravity, the cohesion of the particles pulling the remaining water along, and while this is the main effect it isn’t the only one that is present. If the pressure in the tube drops low enough, you would form low-pressure voids, but these are prevented by the atmospheric pressure on the fluid. Siphons have been shown to work in vacuum, but I would guess this is under some limited set of circumstances. Fill a tube, then turn it upside-down and put the end in a pool of the same fluid, and you will get a void at the closed end if the tube is tall enough — you’ve made a barometer. A siphon is going to run into this problem, and the height at which any given fluid will do so depends on the atmospheric pressure.