COBE and COBRA: “The experiment that confirmed – and almost beat – COBE” from Physics Today (2018). I did not know about COBRA until I read this physics today article. I found the PRL paper (1990) was easier to read and present to the students. For example, COBRA paper shows the acceleration of the rocket launch. The history of COBE vs COBRA is interesting, and it is nice to have an opportunity to acknowledge the importance of confirmation.
“Max the Demon vs Entropy of Doom”: It is a graphic novel with many physics jokes. It even goes into some discussions about entropy and information, featuring many physicists such as Thompson, Carnot, Boltzmann, and Feynman.
Computer assignments: (1) Given a formula like the blackbody radiation or speed distribution of ideal gas, make a plot at different temperatures. Find the maximum (wavelength or speed). (2) Calculate the first 50 terms of the Boltzmann factor (e.g., for rotational degree of freedom, which does not have analytical solution, unlike vibration). Find the sum (as an estimate of the partition function) and plot a bar graph as a function of angular momentum quantum number, L. Find out which state has the largest occupancy.
2018 was a fun year to teach thermal physics. At Drew, this course is offered every other year, using a textbook by the late Dr. Ashley Carter. The Chapter 18 in the textbook is about blackbody radiation, and students (and I) enjoy wrapping up the course with some reviews of Bose-Einstein statistics (i.e., counting the number of microstates for photons), optimization of entropy with Lagrange multiplier, calculation of degeneracy, etc.
Using some modern physics (e.g., E = hv = hc/lamda), students then are able to derive the formula for the blackbody radiation in the same form as appears in Planck’s 1901 paper. In the class, I distribute English-translation of this classic paper, and go over the broad outline. I point out interesting terminologies like “complexion” that Planck used. Also, Planck’s N and P correspond to w and N in our textbook’s notation, respectively. Planck’s paper ends with experimental estimates for h and k.
One of the big science news in 2018 was the re-definition of SI units, by fixing the values of the fundamental constants, including h and k. After ~100 years since the beginning of quantum mechanics and modern statistical mechanics by Planck and Boltzmann, the constants that are named after them have been deemed so fundamental that the units of mass (kg) and temperature (K) have now been defined in terms of their values. What a big paradigm shift! See nist.gov for more details.