March 14, 2015

March 14, 2015

Today is 3-14-15 @9:26.  Hmmm, sounds really familiar??  Ooh,  Pi, that ubiquitous number from my engineering days.  It crept into calculations all the time.  Aimee and I are on the campus of the University of Arizona where they are celebrating this once a century International Pi Day.  Quite by accident, for it is also the site of the Tucson Book Festival.  This event is very popular with hundreds of booths set up on the Main Mall.  While some of the exhibitors are interesting, I really dragged Aimee here because two of the University science labs are world famous and are having a free open house.

Our first stop is the Science City booth where we get the last of the 10am tour tickets for the Steward Observatory Mirror Lab.  A couple years ago we attended a star show at their observatory atop our local Mt Lemmon.  It was outstanding and I have been wanting to see this sister facility.  This astronomy lab has pioneered the manufacture of the world’s largest telescope mirrors.  The 30-minute tour gives us a peak into the cutting edge technology necessary to manufacture these enormous mirrors.  The process starts with Pyrex-type glass from Japan that is melted and spun to approximate a parabolic shape.  The glass is then polished for years to produce the excruciatingly fine level of precision.  The mirror has a honeycomb structure to reduce weight and temperature distortion.  The first mirror took six years to complete.

When finished, seven of these mirrors will be combined in an array and installed in the Giant Magellan Telescope atop a mountain in Chile.  It will have the effective resolving power of an 80-foot diameter telescope.  This compares to the 200-inch Hale Telescope that was the largest for most of my lifetime.  That Hale mirror took 13 years to polish!

While we are on the campus, we also took the opportunity to tour Arizona’s Tree Ring lab.  One of the university astronomers pioneered the science of dendrochronology.  This method of dating involves collecting wood samples from all over the world and counting the number and size of the tree’s growth rings.  By analyzing thousands of overlapping tree samples, scientists have assembled complete tree ring histories going back over 10,000 years allowing dating of unknown wood samples to the EXACT year.

I guess it was appropriate that we toured both of these labs on Pi day, because both involve really big circles, albeit one glass and the other wood.