"If you have one clock ... you are peaceful and have no worries," says Van Baak, fingering a length of cable connecting two of his machines. "If you have two clocks ... you start asking, 'What time is it, really?'"
He wanted his children to see that relativity is proportional. So he loaded the family's blue minivan with portable power supplies, monitoring equipment, and three HP 5071 cesium clocks. Three, because time is always marked relative to other clocks: More clocks mean more accurate time. With his three kids and some camping gear in tow, he drove the winding roads spiraling up Washington's Mt. Rainier and checked the family into a lodge 5,319 feet above sea level.
They hiked the trails, and the kids relaxed with board games and books, while in the imperceptibly lessened gravity, time moved a little bit faster than at home. Van Baak found himself explaining to park rangers more than once why a minivan filled with inscrutable equipment was idling in front of the national park lodge for hours on end. But the effort paid off. When the family returned to the suburbs two days later, the cesium clocks were off by the precise amount relativity predicted. He and his family had lived just a little more life than the neighbors.
"It was the best extra 22 nanoseconds I've ever spent with the kids," Van Baak says.