Daily Archives: February 18, 2010

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.

Outsourcing

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In the era where poor scores mean punishment for the school, there appears to be a new form of cheating: the teachers or administrators changing the answers after the exam has been completed.

Georgia Schools Inquiry Finds Signs of Cheating

The erasure analysis used the same scanners that score tests to count the erasures in which answers were changed from wrong to right. “It’s not any sort of crazy technology,” Ms. Mathers said. “You just beef up the scanner so it can read varying degrees of gray scale.”

The study determined the average number of wrong-to-right erasures statewide for each grade and subject, and flagged any classroom with an unusually high number. For example, in fourth-grade math, students on average changed 1.8 answers from wrong to right, while one classroom that was flagged as suspicious had more than 6 such changes per student.

One Thing's for Certain

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I ran a cross a few infographics recently, while surfing the web because it was too snowy outside to do anything, and I was avoiding doing my own taxes, so I looked at everyone else’s.

The US federal budget, showing the inflows and outflows, broken down into several categories. One thing struck me: income tax revenue is only slightly larger than payroll tax revenue. In many political arguments about tax cuts, it’s only income tax that is mentioned, and the income tax burden is touted. But that’s missing half of the picture, because the payroll taxes are regressive; there are people who pay no income tax but pay a significant fraction of their income in payroll taxes, and are not helped by income tax cuts.

So if you analyze the tax burden incorporating the payroll taxes (as well as state and local taxes), what does the picture look like? It’s only slightly progressive — not the portrayal of woe that some would have you believe.