This post is an analysis of "Changes of decay rates of radioactive 111In and 32P induced by mechanic motion" by YuJian He, Fei Qi and ShengChu Qi, located at http://www.springerlink.com/content/x1q13217t2427059/
Summary: Two different radioactive isotopes were put in a centrifuge and spun. The half-life appeared to increase if spun one way and decrease if spun the other way.
Claim: There is a difference and it can be explained by the chiral dependence of the weak force.
Question 1: Are the results "Significant"?
Statistically, is the proof strong enough to not just be a coincidence? Well... somewhat. For 111In they measure a "natural" half life of 2.83 +/- 0.03 days, clockwise is 2.75 +/- 0.03 days, and anticlockwise it is 2.88 +/- 0.03 days. None of this is the "3 sigma" difference which is necessary in particle physics (though not other fields) to claim an observation.
For 32P the natural is 14.29+/-0.03 days, clockwise is 13.75+/-0.03 days, and anticlockwise is 14.54 +/- 0.03 days. This is a "significant" observation if those errors are true.
It is somewhat unclear where these errors are coming from. They claim to fit their data in Excel, so perhaps that spit out a fit uncertainty. However, they quote the SAME errors for the other isotope even though the half life is an order of magnitude different. They don't provide any measure of "how good" their fit is - like a chi2 test.
Answer: Some of their results do not appear to be statistically significant. Their error bars are not explained so significance cannot really be judged. I can't say their results are "wrong", but they are not good science
Question 2: Is the mechanism they explain the effect with reasonable?
This is dangerous territory since they appear to be chemists and anything effecting radioactive decay half life would be a physics process. Unfortunately this section is poorly written, presumably because English is their second language. This makes it somewhat difficult to tell if what they are saying is nonsense or if it just sounds this way. The general idea is that elementary particles have a property called chirality that relates to spinning clockwise or counterclockwise. It appears as if the authors of this paper try to relate chirality to all sorts of things.
The first problem is that the "physics paper" they cite to discuss the chiral nature of the Weak Force is a Scientific American paper from 1990. This is scary! Scientific American has articles on whether robots will rule the world any time soon. It is not a good source for citing the fundamental rules of the universe. Yes, there is a preference for particles to "spin" clockwise vs counterclockwise. I don't think the authors understand what this means.
Spin is a technical term in physics and is inherently quantum mechanical. It is possible to align the spins of particles, but it must be done on a quantum mechanical level. The authors haven't modified the orientation of the spins of the atoms in their sample (for instance, by putting them in a very strong magnetic field like in MRI or cooling them down to almost 0 kelvin) so they will be randomly distributed. Basically, the motion of the centrifuge in this paper is too "big" for the individual atoms/particles to know that there is a difference between clockwise and anticlockwise.
Answer: No, they seem to misunderstand the physics concept they are citing
Final Conclusion: The most generous judgment is that they misunderstood the physics process and didn't properly consider their sources of measurement error. I would judge it "Sloppy Science" and am surprised it was published in a peer reviewed journal. Perhaps the reviewers didn't understand the physics either.
No comments:
Post a Comment