Gulf Coast Undergraduate Research Symposium!

Rice University's schools of Natural Sciences and Engineering want to make sure that when talented science and engineering undergraduates in the US are deciding where to apply for graduate school, we are on their radar, so to speak.  To that end, we are hosting our second annual Gulf Coast Undergraduate Research Symposium.  To quote the webpage,

The Gulf Coast Undergraduate Research Symposium (GCURS) is a forum for undergraduate researchers to present original research discoveries.... GCURS fosters intercollegiate interactions among students and faculty who share a passion for undergraduate research. We expect several hundred speakers from about half of the states. The event also offers a friendly and supportive environment to students who would be giving their first formal research presentation, and faculty will provide written constructive feedback.

The registration deadline is Sept. 29.  Breakfast, lunch, and dinner will be provided on Saturday, and travel expenses for students (hotel, mileage, airfare if preapproved) will be covered by Rice's Office of Graduate and Postdoctoral Studies.  Please pass this along - it's a fun time.  If you want more details and contact information either for our department's role or the meeting as a whole, please let me know.

Amazon book categories are a joke

A brief non-physics post.  Others have pointed this out, but Amazon's categorizations for books are broken in such a way that they almost have to be designed to encourage scamming.  As an example, my book is, at this instant (and that's also worth noting - these things seem to fluctuate nearly minute-to-minute), the number 30 best seller in "Books > Science & Math > Physics > Solid State Physics".  That's sounds cool, but it's completely meaningless, since if you click on that category you find that it contains such solid state physics classics as "Ugly's Electrical References, 2014 ed.", "Barron's 500 Flash Cards of American Sign Language", "The Industrial Design Reader", and "Electrical Motor Controls for Integrated Systems", along with real solid state books like Kittel, Simon, and Ashcroft & Mermin.  Not quite as badly, the Nanostructures category is filled "Strength of Materials" texts and books about mechanical structures.  Weird, and completely fixable if Amazon actually cared, which they seem not to.

Proxima Centauri's planet and the hazards of cool animations

It was officially announced today that Proxima Centauri has a potentially earthlike planet.  That's great, especially for fans of science fiction.  Here is a relevant video by Nature:

Did you spot the mistake?  The scientists discovered the planet by seeing the wobble in the star's motion (measured by painstaking spectroscopy of the starlight, and using the Doppler shift of the spectrum to "see" the tiny motion of the star).  The animation tries to show this at 0:55-1:12.  The wobble is because the star and planet actually orbit around a common center of mass located on the line between them.  Instead, the video seems to show the center of mass of the star+planet tracing out a circle around empty space.  Whoops.   Someone should've caught that.  Still an impressive result.

Update:  The makers of the video have updated with a link to a more accurate animation of the Doppler approach:  https://youtu.be/B-oZYm3L1JE.

Statistical and Thermal Physics

Eight years ago I taught Rice's undergraduate Statistical and Thermal Physics course, and now after teaching the honors intro physics class for a while, I'm returning to it.   I posted about the course here, and I still feel the same - the subject matter is intellectually very deep, and it's the third example in the undergraduate curriculum (after electricity&magnetism and quantum mechanics) where students really need to pick up a different way of thinking about the world, a formalism that can seem far removed from their daily experience.

One aspect of the course, the classical thermodynamic potentials and how one goes back and forth between them, nearly always comes across as obscure and quasi-magical the first (or second) time students are exposed to it.  Since the last time I taught the course, a nice expository article about why the math works has appeared in the American Journal of Physics (arxiv version).  

Any readers have insights/suggestions on other nice, recent pedagogical resources for statistical and thermal physics?  

Updated - Short items - new physics or the lack thereof, planets and scale, and professional interactions

Before the start of the new semester takes over, some interesting, fun, and useful items:

Update:. This is awesome.  Watch it.

• The lack of any obvious exotic physics at the LHC has some people (prematurely, I suspect) throwing around phrases like "nightmare scenario" and "desert" - shorthand for the possibility that any major beyond-standard-model particles may be many orders of magnitude above present accelerator energies.  For interesting discussions of this, see here, here, here, and here.  
• On the upside, a recent new result has been published that may hint at something weird.  Because protons are built from quarks (and gluons and all sorts of fluctuating ephemeral stuff like pions), their positive charge has some spatial extent, on the order of 10^-15 m in radius.  High precision optical spectroscopy of hydrogen-like atoms provides a way to look at this, because the 1s orbital of the electron in hydrogen actually overlaps with the proton a fair bit.  Muons are supposed to be just like electrons in many ways, but 200 times more massive - as a result, a bound muon's 1s orbital overlaps more with the proton and is more sensitive to the proton's charge distribution.  The weird thing is, the muonic hydrogen measurements yield a different size for the proton than the electronic hydrogen ones.  The new measurements are on muonic deuterium, and they, too, show a surprisingly smaller proton than in the ordinary hydrogen case.  Natalie Wolchover's piece in Quanta gives a great discussion of all this, and is a bit less hyperbolic than the piece in ars technica.
• Rumors abound that the European Southern Observatory is going to announce the discovery of an earthlike planet orbiting in the putative habitable zone around Proxima Centauri, the nearest star to the sun.  However, those rumors all go back to an anonymously sourced article in Der Spiegel.  I'm not holding my breath, but it sure would be cool.
• If you want a great sense of scale regarding how far it is even to some place as close as Proxima Centauri, check out this page, If the Moon were One Pixel.
• For new college students:  How to email your professor without being annoying.
• Hopefully in our discipline, despite the dire pronouncements in the top bullet point, we are not yet at the point of having to offer the physics analog of this psych course.
• The US Department of Energy helpfully put out this official response to the Netflix series Stranger Things, in which (spoilers!) a fictitious DOE national lab is up to no good.  Just in case you thought the DOE really was in the business of ripping holes to alternate dimensions and creating telekinetic children.

Why is desalination difficult? Thermodynamics.

There are millions of people around the world without access to drinkable fresh water.  At the same time, the world's oceans contain more than 1.3 million cubic kilometers of salt water.  Seems like all we have to do is get the salt out of the water, and we're all set.   Unfortunately, thermodynamics makes this tough.  Imagine that you have a tank full of sea water and magical filter that lets water through but blocks the dissolved salt ions.    You could drag the filter across the tank - this would concentrate the salt in one side of the tank and leave behind fresh water.  However, this takes work.  You can think about the dissolved ions as a dilute gas, and when you're dragging the membrane across the tank, you're compressing that gas.  An osmotic pressure would resist your pushing of the membrane.  Osmotic effects are behind why red blood cells burst in distilled water and why slugs die when coated with salt.  They're also the subject of a great Arthur C. Clarke short story.

In the language of thermodynamics, desalination requires you to increase the chemical potential of the dissolved ions you're removing from the would-be fresh water, by putting them in a more concentrated state.   This sets limits on how energetically expensive it is to desalinate water - see here, slide 12.   The simplest scheme to implement, distillation by boiling and recondensation, requires coming up with the latent heat of the water and is energetically inefficient.  With real-life approximations of the filter I mentioned, you can drive the process, called reverse osmosis, and do better.  Still, the take-away message is, it takes energy to perform desalination for very similar physics reasons that it takes energy to compress a gas.

Interestingly, you can go the other way.  You know that you can get useful work out of a gas reservoirs at two different pressures.  You can imagine using the difference in chemical potential between salt water and fresh water to drive an engine or produce electricity.  In that sense, every time a freshwater stream or river empties into the ocean and the salinity gradient smooths itself by mixing of its own accord, we are wasting possible usable energy.  This was pointed out here, and there is now an extensive wikipedia entry on osmotic power.