At 6, given a shiny penny to throw into the tinkling fountain at the mall we visited once a year in order to buy school clothes, I knew exactly what to wish for. I closed my eyes tight, imagined the elegant, stately horse I knew would be mine one day, and threw the penny into the water, feeling that odd mix of anticipation for something wonderful happening someday and regret for having thrown something valuable away. At 7 in the car, we’d pass horses sometimes. Living in what was once a cowtown and now was an emerging bedroom community of physicists and engineers and their kids, we were surrounded by…