Tonight the sun rises over Copernicus, one of the most magnificent craters on the moon. Unlike the gaping potholes waiting to jar your car this season, a smooth ride is guaranteed. At 58 miles (93 km) across and set off by itself like an old oak tree in a big field, it’s easy to see even in binoculars as a bright ring alongside the terminator. The terminator marks the division between day and night on the moon. From new moon to full, as phase of the moon increases, it’s the advancing line of sunrise. After full moon, when the moon’s phase wanes, it’s the advancing line of night.