At first, Carl Lampland didn’t notice anything out of the ordinary, on that Tuesday afternoon. It was getting on for 4 o’clock; the working day was nearly over. Through the window of his workroom, in the grounds of Lowell Observatory, he could see the sharp lines of the fir trees set against the cold, bright blue sky. It was February 18, 1930 and, for some reason, it was quieter than normal. Something was missing.