Comments for Uncertain Principles

Comment on Of Controversies and Clocks by Anonymous2

Anonymous2 — Thu, 20 Jun 2013 02:42:14 +0000

Re: Compton Clock

I also don’t see how the two isotopes would resolve anything. The issue as I see it is that they are essentially measuring the recoil frequency, from which h/m (the ‘Compton frequency’ is just this ratio divided by c^2) can be determined once the laser frequency is measured; instead of explicitly measuring the laser frequency, they use a self-referenced frequency comb to enable feedback from the interferometer phase to the frequencies in the system, effectively making an ‘implicit’ measurement of the laser frequency … so as far as I can tell the only thing new about the ‘Compton clock’ is this implicit vs explicit determination of the laser frequency, and the fact that there is a physical output that has been stabilized. This last part works because of a clever arrangement where there is one frequency from which all of the laser frequencies, detunings, etc are derived.

If there are two different isotopes being used, one would expect to see the different frequencies because it is essentially an h/m measurement, as other past atom interferometer systems have been.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by damigiana

damigiana — Wed, 19 Jun 2013 06:43:33 +0000

Emmy Noether. Because I’m fed up with people thinking a minor thinking like the theorem all physicists have heard of is all she did. Also, it’s good for boys and girls to remember that women can be scientists, even if they have to jump through many, many more hoops than men to achieve it.
A good alternative: Lise Meitner. One can include details like her not being allowed to high school, having to pee in the restaurant in front of the physics institute because the latter had no women’s restrooms, and Hahn not even mentioning her name in the Nobel acceptance speech, even though she was present.

Comment on Of Controversies and Clocks by Anonymous2

Anonymous2 — Wed, 19 Jun 2013 02:09:55 +0000

from Anonymous:

“For the Compton clock, the photon energy dependence is removed. This is demonstrated in the paper – unlike in the recoil measurement, the photon energy can be changed without affecting the measured frequency, which now depends only on the mass of the atom.”

I don’t think this is true. First of all, the frequency w_m still has N in it, which characterizes the laser frequency. Second, in Fig. 3, the measured w_m does indeed change; only when it is multiplied by (2nN^2) (the curve referenced to the right axis) is the data ‘constant’. The only new feature that I can figure is that the laser used for the interferometer is self-referenced and stabilized – in that way there is no need to make a separate laser frequency measurement to determine h/m (or h/mc^2), as is done in past recoil measurements. Of course, a common way to make a laser frequency measurement is to use a frequency comb to determine its frequency with respect to a known microwave or radio frequency.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by TinyGrasshopper

TinyGrasshopper — Wed, 19 Jun 2013 00:21:48 +0000

Von Neumann. I haven’t read MacRae’s book but I’ve heard it’s a bit lacking on some science-y parts.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by cope

cope — Tue, 18 Jun 2013 22:49:55 +0000

Just showing my geocentric nature here (if non-physicists are not being excluded from your list) but Alfred Wegener hits a lot of bullet points. The profession of geology derisively dismissed him, his commitment was unequaled (how many other great scientists have actually died trying to gather data to support their ideas) and he was posthumously proven to be correct. Also, too, there is the crossover nature of his academic pursuits from the area of his initial expertise (meteorology/climatology) to a subject born simply out of his natural born curiosity, geology.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by Paul

Paul — Tue, 18 Jun 2013 19:42:42 +0000

I vote for Wolfgang Pauli and for Werner Heisenberg.
Maxwell already has recent biography by Basil Mahon “The Man Who Changed Everything: The Life of James Clerk Maxwell”

Comment on Quasi Poll: Most Needed Pop-Science Biography? by Eric Lund

Eric Lund — Tue, 18 Jun 2013 17:13:24 +0000

Anybody who was important enough to get an SI unit named after him deserves a good pop-science biography. There is some value in knowing, for example, why pressure is measured in pascals. Some of them already do, such as Newton. But many of them don’t, at least that I am aware of. The candidate list includes Watt, Joule, Ampère, Coulomb, Henry, Siemens, and a few others.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by Nick Theodorakis

Nick Theodorakis — Tue, 18 Jun 2013 16:42:43 +0000

I nominate Gilbert Lewis, the chemist who never won a Nobel who deserved one the most.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by Dave Munger

Dave Munger — Tue, 18 Jun 2013 16:33:35 +0000

Barnum Brown, dinosaur hunter extraordinaire. At least there wasn’t a good bio of him 12 years ago when my son had to do a class project on him.

Comment on Quasi Poll: Most Needed Pop-Science Biography? by Chad Orzel

Chad Orzel — Tue, 18 Jun 2013 16:20:21 +0000

That is pretty amazing. I assumed there must be a good Maxwell bio out there somewhere.