Monday, February 20, 2023

Science and how it will be practiced in the future

I just registered for an event that celebrates the 35th anniversary of a particular science and engineering program, and one question they posed was, to paraphrase, "Science has changed a lot in the last 35 years.  Please make three predictions about science in the next 35 years."  

I'd be curious for readers' views on this.  My quick take:

  • There will be far more AI/machine learning/software agent-assisted activity.  That seems a certainty, and hopefully it may alleviate some repetitive drudgery in certain types of research.
  • Hopefully I am wrong about this, but I have a feeling that we are still trending in the direction of a widening divide between "have" and "have not" research universities, in terms of having the financial resources to do leading science and engineering research.
  • Foundation investments may be a growing portion of basic research support, for good or ill.  Governmental agencies will face increasing constraints on finances and pressure to concentrate more on short-term and applied work with some claimed quick benefit to economic competitiveness or national security.  

Thursday, February 09, 2023

Tour de force work: Bragg, diffraction, and diamond

There are some examples of scientific progress that just seem so far above and beyond the norm, it's almost jaw dropping in terms of the mental leap needed for the insight.  One example that I always liked to point out to first-year undergrads learning about gravity is Johannes Kepler in 1601-1609 analyzing Tycho Brahe's data by hand (obviously) and deducing that planets move in elliptical orbits and the associated laws of planetary motion.  Imagine staring at page after page of hand-written numerical tables and somehow seeing that.  

Left: X-ray diffraction from single-crystal 
diamond. Right: Bragg's calculation of where
the spots would be if diamond had what we
now know is the correct structure.
Another example from condensed matter physics is the 1912 discovery by William Lawrence Bragg, then 25 years old, that he could deduce the crystal structure of solids from the positions of the spots revealed on photographic film as the solid diffracted a beam of x-rays.  The very fact of diffraction of x-rays by crystals had only been found earlier the same year by von Laue and collaborators.  Bragg had the insight that interference effects due to the x-rays bouncing off different planes of atoms would determine the pattern of spots, as constructive interference only takes place for certain combinations of directions for a given wavelength of x-rays.  The image here is based on Figs. 11 and 12 from this paper, "The Structure of Diamond", by Bragg and his father (who built the diffractometer!).  That was published back-to-back with the more general (and single-author!) paper, "The Structure of some Crystals as Indicated by Their Diffraction of X-rays", where Bragg wrote what is now known as Bragg's Law and the prescription for finding the distance between adjacent planes of atoms.  Imagine looking at the smudgy spots on the photographic plates, having the "aha!" insight about the origin of the pattern, and having the raw computational prowess to just go ahead and calculate it.  Unreal.

Sunday, February 05, 2023

Some interesting links - useful lecture notes, videos

Proposal writing, paper writing, and course prep are eating a lot of my bandwidth right now, but I wanted to share a few things:

  • David Tong at Cambridge is a gifted educator and communicator who has written lecture notes that span a wide swath of the physics curriculum, from introductory material on mechanics through advanced graduate-level treatments of quantum field theory.  Truly, these are a fantastic resource, made freely available.  The link above goes to a page with links to all of these.
  • In a similar vein, Daniel Arovas at UC San Diego has also written up lecture notes on multiple components of physics, though usually aimed at the graduate level and not all linked in one place.  These include (links to pdf files) mechanics, thermodynamics and statistical mechanics, condensed matter physics, nonlinear dynamics, the quantum Hall effect, and group theory (unfinished).
  • I long ago should have mentioned this youtube channel (Kathy Loves Physics and History), by Kathy Joseph.  Her videos are a great blend of (like it says on the label) physics and history of science.  As a great example, check out the story of Ohm's Law.  I had never heard about the dispute between Ohm and Ampère (who didn't know about the internal resistance of batteries, and thus thought his experiments disproved Ohm's law).  
  • This twitter thread pointing out that current in quantum Hall and related systems is not, in fact, purely carried by states at the sample edges, is thought-provoking.