Each spring, thousands of nerds arrive in Pittsburgh for Spring Carnival at Carnegie Mellon University.  Being one of those nerds (and an alumnae), the event has a special place in my heart. Pittsburgh weather for the event is totally unpredictable.  This morning, it was sunny and 75F on campus, while right now it is cloudy with thunderstorms.  I hope to make it to Carnival Midway later tonight if it is open to see the Booths this year. This morning I went to Sweepstakes, affectionately known as Buggy.  (I know you Pittsburgh natives are thinking of the word we use to identify a shopping cart — but)  A  “buggy” is a…