GR Clears Another Hurdle

Environmental & Science Education, STEM, Nature of Science, History of Science

Ed Hessler

I overlooked the following report from Science News (SN) when it was first published. Symmetry re-published it with the by-line... Another test of a key principle of Einstein's theory of general relativity.

You might want a refresher on the equivalence principle before you read further and here is a lesson (8m 54s ) by theoretical physicist Sabine Hossenfelder who is quoted in the SN report. You know that you have two viewing choices: the blog report which includes a written transcript directly below and her YouTube channel which doesn't have the transcript unless you are a subscriber. 

I'm also including a video (6m 14s) by Paul Anderson, who was an AP physics teacher, Bozeman, Montana and now is an educational consultant and YouTube creator known (Bozeman Science). Anderson was a workshop leader at the annual MnSTA conference in Mankato  (MnCOSE 15, 2015). 

The Anderson video is shorter and included because I thought you might like to learn about the principle  from two perspectives, what an AP physics student is expected to know as well as one pitched at a higher level, say college/interested adult. AP Physics is algebra based while college physics is calculus based.

James Riordan who wrote the SN (9/14/2022) report provides the take home message in the first paragraph. "Gravity doesn't discriminate. An experiment in orbit has confirmed with precision a hundred times greater than previous efforts, that everything falls the same way under the influence of gravity." But please don't stop reading it.

The essay includes background, discussion of the hope by many physicists for a unified theory, known as the theory of everything, a definition (and you may want to compare notes with the explanations above), details of the experiment known as the MICROSCOPE experiment (a satellite), and what's planned next which, in the 2030s is another launch with an even better and more sensitive measuring devices.

Riordan quotes Dr. Hossenfelder on the expectations of theoretical physicists in the current experiment.  “'These tests aren’t just about the equivalence principle. They implicitly look for all other kinds of deviations, new forces and so on' "that aren’t part of general relativity." '“So really it’s a multiple-purpose, high-precision measurement.'”

And what goes up will come down. The experiments were conducted in platinum cylinders, which cost about 2 million Euros (~2 million US, 2022). The satellite impact  is expected in about 25 years in case the dosh attracts you. Where? It will be years before the location will be known and you will have to wait until that date is close.

One of the underlying themes of the Riordan story is about how science works which in this case is really important due to its centrality to a powerful theory in theoretical physics. It includes checking and rechecking measurements, especially as techniques improve, the slant a new line of evidence brings, and the development of even better technical measurements and during the interval until the next launch. In other words, getting the science right.