When a group of dignitaries and journalists made a rare foray to the roof of the White House, Jimmy Carter had something to show them: 32 solar water-heating panels. “A generation from now,” the US president declared, “this solar heater can either be a curiosity, a museum piece, an example of a road not taken, or it can be just a small part of one of the greatest and most exciting adventures ever undertaken by the American people.” What happened next is the stuff of tragic what-ifs and what-might-have-beens. “It did become a curiosity, it is a museum piece and