by Rex Parker, PhD
director@princetonastronomy.org

The Ides of March Approacheth — Yet We Shall Nonetheless Meet.  Shakespeare showed how the Ides of March (mid-month marked by the full moon) were treacherous times for Julius Caesar, but we’ll fearlessly convene at Peyton Hall auditorium on the Princeton University campus on Tues March 11 (7:30pm).  Our guest speaker will be J. Richard Gott III, Emeritus Professor of Astrophysical Sciences at Princeton University.  If you’re a newer member, be aware that due to the continuing campus construction project near Peyton Hall, automobile parking is in the garage at 148 FitzRandolph Rd, accessed from Faculty Rd, giving you a ~10 to 15 minute walk around the stadium to Peyton.  If you just can’t make it physically, this again will be a hybrid meeting via Zoom;  members receive the link by e-mail a few days in advance, and the Zoom link will also be on the AAAP website.  For more information on the presentation and a walking route map to Peyton Hall, see Program Chair Victor’s article below.

Member Rich Sherman will do the Un-journal Club (from his AAAP-tropical abode in Florida) after the break this month.  He’ll talk about his recent trip to famed Kitt Peak observatories near Tucson AZ.  The un-journal club is a monthly tradition where a member gives a brief informal and fun presentation to begin the second half of the meeting.  “Un-journal” means this is not grad school, you don’t need scholarly journal-like topics, just what you care about in astronomy.  PowerPoint slides, JPEG’s, astro-images, travel pictures, book reviews, your imagination is the limit (bring a USB memory stick). To get onto the schedule for an upcoming meeting, please contact me or program chair Victor Davis (program@princetonastronomy.org).

Light Speed and the Invention of Interferometry. The fascinating presentation last month by Kim Burtnyk from the LIGO observatory in Hanford WA got me wondering how interferometry was invented.  A major necessary step was the accurate determination in 1862 of the speed of light by Leon Foucault in France, probably more famous for his pendulum which demonstrated earth’s rotation. Albert Michelson in the US in 1879 refined and improved the method for light speed. By creating robust methods for precisely manipulating light beams through controlled reflection, their apparatus for light speed were keystones in the subsequent invention of the interferometer by Michelson in 1881. In 1907 Michelson became the first American to receive the Nobel prize.  From a wonderful biography, The master of light: A biography of Albert A. Michelson, written by his daughter Dorothy Michelson Livingston, I learned a lot more about the man and the scientist. How he extended and improved upon Foucault’s method and succeeded in accurately determining the speed of light so many decades before electronics were developed is an amazing story. 

Albert Michelson was born in Prussia (now Poland) in 1852 and emigrated to the US with his parents at the age of two. They journeyed across the sea and surmounted dangers in crossing the Panama isthmus years before the canal, settling in a wild west California gold rush town in the Sierra Nevada. Albert’s early promise led to his appointment by President Grant to the Naval Academy in Annapolis in the post- civil war years. It was there that, as an ensign in the Navy, he recreated Foucault’s light speed apparatus. The basis for the method was the measurable displacement of a light beam reflected from a rotating mirror, with calculations using a geometric equation. Of course, it was much harder than that may sound!  In 1862 Foucault obtained c = 298,000 km/sec. Michelson with refined instrumentation obtained c = 299,944 km/sec (186,376 mi/sec), within 0.05% of today’s accepted figure! Accuracy here matters in countless ways for today’s precision electronics and GPS world, for example the meter is determined by the speed of light itself. Delving deeply into the instrumentation Foucault and Michelson figured out in the mid-late 1800’s is a fascinating read. 

Going into the Field.  We’re considering possible destinations for AAAP field trips It’s been years since our private tour of the PPPL in Princeton, and nearly a decade ago a group of us made an unforgettable field trip to D.C. to see the Smithsonian Air & Space Museum and the US Naval Observatory in Washington D.C.  Now we are considering a visit to the other National Air and Space Museum, the Udvar-Hazy Center near Dulles Airport outside.  If you have other proposals for a field trip, we would like to hear about it.