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Sun Dec 2, 2012, 09:58 AM

New experiments challenge fundamental understanding of electromagnetism

A cornerstone of physics may require a rethink if findings at the National Institute of Standards and Technology (NIST) are confirmed. Recent experiments suggest that the most rigorous predictions based on the fundamental theory of electromagnetism—one of the four fundamental forces in the universe, and harnessed in all electronic devices—may not accurately account for the behavior of atoms in exotic, highly charged states.

The theory in question is known as quantum electrodynamics, or QED, which physicists have held in high regard for decades because of its excellent track record describing electromagnetism's effects on matter. In particular, QED has been especially useful in explaining the behavior of electrons, which orbit every atomic nucleus. But for all of QED's successes, there are reasons to believe that QED may not provide a complete picture of reality, so scientists have looked for opportunities to test it to ever-increasing precision.

One way to test parts of QED is to take a fairly heavy atom—titanium or iron, for example—and strip away most of the electrons that circle its nucleus. "If 20 of titanium's 22 electrons are removed, it becomes a highly charged ion that looks in many ways like a helium atom that has been shrunk to a tenth its original size," says NIST physicist John Gillaspy, a member of the research team. "Ironically, in this unusual state, the effects of QED are magnified, so we can explore them in more detail."

Among the many things QED is good for is predicting what will happen when an electron orbiting the nucleus collides with a passing particle. The excited electron gets bumped up momentarily to a higher energy state but quickly falls back to its original orbit. In the process, it gives off a photon of light, and QED tells what color (wavelength) that photon will have. The NIST team found that electrons in highly charged helium-like ions that are excited in this fashion give off photons that are noticeably different in color than QED predicts.

Read more at: http://phys.org/news/2012-11-fundamental-electromagnetism.html

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Reply New experiments challenge fundamental understanding of electromagnetism (Original post)
Bosonic Dec 2012 OP
DreamGypsy Dec 2012 #1
longship Dec 2012 #2
eppur_se_muova Dec 2012 #4
DreamGypsy Dec 2012 #5
AlecBGreen Dec 2012 #3

Response to Bosonic (Original post)

Sun Dec 2, 2012, 10:52 AM

1. Oh, another sensational title for a semi-popular science article.

Last edited Mon Dec 3, 2012, 05:51 PM - Edit history (1)

Popular science magazine articles are not peer reviewed and, while they are intended to convey real, accurate scientific information, they also have to sell magazines.

To have a measurement that is at variance with the predictions of a well-supported theory does not immediately "challenge fundamental understanding" of that theory.

Here's the synopsis from the Physical Review Letters:

Received 11 May 2012; published 10 October 2012

We report a new test of quantum electrodynamics (QED) for the w ( 1s2p¹P₁→1s²¹S₀ ) x-ray resonance line transition energy in heliumlike titanium. This measurement is one of few sensitive to two-electron QED contributions. Systematic errors such as Doppler shifts are minimized in our experiment by trapping and stripping Ti atoms in an electron beam ion trap and by applying absolute wavelength standards to calibrate the dispersion function of a curved-crystal spectrometer. We also report a more general systematic discrepancy between QED theory and experiment for the w transition energy in heliumlike ions for Z>20. When all of the data available in the literature for Z=16–92 are taken into account, the divergence is seen to grow as approximately Z3 with a statistical significance on the coefficient that rises to the level of 5 standard deviations. Our result for titanium alone, 4749.85(7) eV for the w line, deviates from the most recent ab initio prediction by 3 times our experimental uncertainty and by more than 10 times the currently estimated uncertainty in the theoretical prediction.


So, just as with the faster than light neutrinos, the relevant scientific community will sit back, analyze the results, attempt to reproduce the observation, speculate on a theoretical basic to explain the observation, and do their jobs. When/if the observation is found to be correct and a theoretical change explains it (either an enhancement/addition to QED or a 'new' theory), then the further predicted implications of that theoretical basis will be explored and measured and the results will ripple through related data and theories. Voila, science advances.

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Response to DreamGypsy (Reply #1)

Sun Dec 2, 2012, 11:11 AM

2. Excellent response.

Thanks for that.

I wanted to respond, but you wrote it better than I ever could have.

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Response to DreamGypsy (Reply #1)

Sun Dec 2, 2012, 06:45 PM

4. For those who care about such details ...

1s2p 1P1 → 1s2 1S0

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Response to eppur_se_muova (Reply #4)

Mon Dec 3, 2012, 05:55 PM

5. Thanks.

I think I got the sub/superscripts correct this time.

I had to add spaces because the subscript 0 and closing paren were converted to a smiley. Sheez.

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Response to Bosonic (Original post)

Sun Dec 2, 2012, 06:32 PM

3. how can they do that!?

"If 20 of titanium's 22 electrons are removed, it becomes a highly charged ion..."

I dont doubt it, its just mind-boggling that such a "naked" atom (+22 charge!?) could be produced.

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