AMO physics

Last week Mike the Mad Biologist linked to an essay by Union College physics professor Chad Orzel, “Particle And Astro Aren’t The Only Kinds Of Physics“.  Orzel’s field is Atomic, Molecular, and Optical (AMO) Physics.  For my Ph.D. research I worked a problem in molecular physics.  It was an experimental test of a very old theoretical problem:  Imagine a hydrogen atom with a huge point electric dipole moment at its nucleus.  What happens to the hydrogenic orbitals and the energy levels as a result of the dipole?  That was one aspect of the problem.  The other was that there is no such thing as an atomic ion with an huge electric dipole moment at its nucleus.  The Rydberg states I was studying had a molecular ion core rather than an atomic one.  The other question I addressed was how an the oscillating dipole affects the exchange of energy and angular momentum between the Ryberg electron and the molecular ion core.  Anyhow, with our backgrounds in AMO physics, Orzel and I share some common experience and common knowledge.  His article resonated with me.  He starts out:

I sometimes get asked why I’m not a particle physicist. This is a question that can have a bit of an edge, particularly when coming from high-energy theorists, a number of whom feel that only second-rate physicists do experimental particle physics, and anyone who studies things larger than the nucleus of an atom might as well be a chemist.

I sympathize.  My lab was the Chemistry Dept.  I’d often get asked why I wasn’t an organic chemist.  Orzel provides a really nice explanation for why he chose the field he did:

I’m in AMO physics by choice, because I find it a particularly congenial field for a number of reasons, some of which I’ll try to explain here…  It’s not too big… [In contrast to particle physics, the] community as a whole is also much smaller… This means you have an excellent chance of getting to see and interact with even the biggest names in the field, who are mostly very down-to-Earth folks…  It’s not too small… The subject matter of AMO physics, as it says right there in the name, involves atoms and molecules, generally very simple molecules by the standards of chemistry. These hit a sort of Goldilocks point, at least for me– they’re small enough to show interesting quantum effects, but not so small that you can’t see them directly… The physics is amazing… It has applications all over… You can even attack the same fundamental physics studied with giant particle colliders using small-scale AMO physics labs….  (As a bonus, [AMO is] also an unusually collegial subfield– even research groups that are in direct competition tend to be on friendly terms with one another…)

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Thought for the Day: 17 June 2015

Nothing in the methods or practices of science guarantees success. But we have a capacity to observe, theorize, measure, and test; and these abilities are crucial to our human ability to navigate an uncertain world. So we should look at the institutions and findings of science much as pragmatists like Israel Scheffler and WVO Quine did: as imperfect but valuable tools on the basis of which to learn some of the more important properties and dynamics of the world around us.

–  Daniel Little

CVPR 2015

I’m attending the Computer Vision and Pattern Recognition (CVPR) conference this week.  I’ve read a lot of papers from past proceedings but this is the first time I’ve attended.  (A few interesting talks and posters but so far nothing particularly applicable to work.  Still a few days to go though.)   Anyhow, best quote so far from the meeting:

You might think that you can move in any direction in the tomato space.

Ah, but you can’t!  In all seriousness, the speaker was talking about a mathematical representation of tomatoes from unripe to ripe to sliced or diced.  More generally, his topic was representation of objects undergoing transformations.  It was an interesting talk.

Orwell’s 1984 was intended as a warning not an instruction manual

Newspeak:

Actually, it gets much worse than just banning (or attempting to ban) words.   They act to suppress inquiry in general and the collection of potentially inconvenient information in particular.  It was bad before the 2014 election.

and then it got worse

(Many of the links above are directly or indirectly via Mike the Mad Biologist.)

You wonder why I believe contemporary Republicans are essentially Stalinists?  Well there you have it.

PS  No, both sides don’t do it.  This is a Republican problem.

Thought for the Day: 18 April 2015

When you’re scientifically literate, the world looks different to you. It’s a particular way of questioning what you see and hear. When empowered by this state of mind, objective realities matter. These are the truths of the world that exist outside of whatever your belief system tells you.

One objective reality is that our government doesn’t work, not because we have dysfunctional politicians, but because we have dysfunctional voters. As a scientist and educator, my goal, then, is not to become President and lead a dysfunctional electorate, but to enlighten the electorate so they might choose the right leaders in the first place.

–  Neil deGrasse Tyson

First Direct Observation of Carbon Dioxide’s Increasing Greenhouse Effect at the Earth’s Surface

It’s kind of amazing to me that it took so long for there to be a direct experimental measurement of CO2 forcing in the field.   Spoiler alert:  Their observations were fully consistent with what theory predicts.

The effects of CO2 on radiative transfer are well-understood but apparently there’s never been direct measurement of radiative forcing at the Earth’s surface.   What’s novel (I think, having read just the Abstract of the paper not the full text) is that they directly measured heat transfer rather than inferring it from a network of temperature sensors (or satellite measurements) and independently verified radiative transfer models.  In short, their measurements are an additional test of things we believed to be true based on other measurements.   Had their measurements not been consistent with model predictions that would have been a big surprise and would merit further investigation.  Bottom line:  The CO2 contribution to net radiative forcing is well-understood.  Anthropogenic CO2 emissions have caused the Earth to retain (and it will continue to retain) a significant amount of heat above what it would without them.   The specifics of where that excess heat ends up – atmosphere near the surface?  oceans? – is a subject of ongoing investigation but make no mistake we’re retaining a massive amount of excess heat.   And bear in mind average surface temperature changes, however small they may seem, are really proxies for much more significant climatological effects.

From Lawrence Berkeley Lab’s press release, “First Direct Observation of Carbon Dioxide’s Increasing Greenhouse Effect at the Earth’s Surface”:

Scientists have observed an increase in carbon dioxide’s greenhouse effect at the Earth’s surface for the first time. The researchers, led by scientists from the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), measured atmospheric carbon dioxide’s increasing capacity to absorb thermal radiation emitted from the Earth’s surface over an eleven-year period at two locations in North America. They attributed this upward trend to rising CO2 levels from fossil fuel emissions.

The influence of atmospheric CO2 on the balance between incoming energy from the Sun and outgoing heat from the Earth (also called the planet’s energy balance) is well established. But this effect has not been experimentally confirmed outside the laboratory until now. The research is reported Wednesday, Feb. 25, in the advance online publication of the journal Nature.

The results agree with theoretical predictions of the greenhouse effect due to human activity. The research also provides further confirmation that the calculations used in today’s climate models are on track when it comes to representing the impact of CO2.

Read or download the paper here.  (It’s $5 to rent and $32 (!!) to buy a copy.   At those prices I recommend visiting your local college or university science library and reading the copy of Nature they have on the shelf.)

Thought for the Day: 23 February 2015

Once S Fred Singer debated Sherry Rowland about ozone depletion on NPR. Every atmospheric scientist I talked to was amused that Rowland had obviously crushed Singer. Non-scientists thought that Singer held up fairly well (he has – he is really old). There is the problem. Competent scientists know that Singer, Soon, Baliunas and Seitz were pedaling BS in their opposition to protecting the ozone layer. Reagan and Bush knew it and they were the ones that provided knowing leadership to the world concerning the Montreal Protocol. And the Protocol has worked. the abundance of ozone depleting substances has decreased and the decrease in global stratospheric ozone has been arrested. The ozone hole will go away in the future if the world stays at it.

Competent scientists know that Soon’s rants about climate are garbage….  What to say about the folks who choose to believe that Soon is a scientist and that his objections to climate science are significant? Put these people in a functional MRI and you find that the part of their brain that responds to his BS is the part that responds to cocaine. It is not the part that does algebra.

If you do associate with denialists, go have coffee with them and listen to them. I send them something from my course first. Like the First Law treatment of climate. Respect and renewables may rewire brains – rants won’t.

That’s the way it is.

–  “James Wilson” in the NYTimes comment section