A Weekend to Reflect

It has been a somber weekend in New York. In a city of many millions, thousands of premature deaths in ninety minutes  left a deep scar.  Among my acquaintances, not everyone knew someone who died, but it seems almost everyone knew someone who knew someone who perished.  And for those of us who watched the towers being built, wandered for years in their shadows, and walked on the roof deck gaping at the astounding view, their destruction and absence from the skyline will be permanently unsettling, and motivating.  I have stood atop that which does not exist; my memory floats in the air.

Three nights ago I was far downtown, and the austere memorial that has graced Manhattan skies each September — a pair of vertical shafts of blue-white floodlight, recalling the towers — was illuminating the sky just overhead.  Several layers of thin clouds caught the light, creating pairs of soft-edged moons stacked one atop the next.  As the wind rushed the clouds along, each moon separately glowed and flickered, yielding a spectacle at once simple and enigmatic — a conjunction of artifice and nature, of the steady and the unpredictable.

There’s much to say about the aftermath of 9/11/01 and the consequences, as far as internal and external U.S. politics, U.S. society and values, and U.S. science in particular. But not right now.

In the next week (two weeks? three?), in between pushing two papers toward completion and preparing a colloquium (= a talk intended for an entire physics department) that I will give a few times this year, I will try to use my last week’s intensive study of the existing papers and talks from the Large Hadron Collider (LHC) to characterize what their measurements tell us so far about nature — and what they don’t tell us.  This isn’t easy, at the very least because [for very general reasonsone typically can’t rule out a class of theories (such as supersymmetry or extra dimensions or technicolor) through a single set of measurements — and conversely, a single measurement says something about many classes of theories.   Given this, should a discussion of LHC results be organized by measurements or by theories?  By empirical data from nature or by the  ideas of the human mind?  These practical questions have a principled side, and the answers illuminate more than we might initially expect.  For what is the best way to summarize our knowledge so that we actually know what we know?