General relativity becomes easier to love when somebody loads atomic clocks into a vehicle, brings the kids, and drives up a mountain to see whether Einstein was serious.
Visit the Project GREAT 2005 tour
That is essentially what happened in September 2005.
Tom Van Baak, a longtime atomic-time hobbyist, took several cesium clocks from home to the Paradise area of Mount Rainier and left them at higher elevation for roughly 42 hours.
The point was simple enough to explain at a kitchen table: clocks higher in Earth’s gravitational field should run slightly faster than clocks lower down.
The expected difference was tiny.
Nanoseconds tiny.
A physics experiment with camping-trip energy
Van Baak later described the net elevation difference between home and the mountain site as about 4,400 feet, or roughly 1,340 meters.
Using the standard low-altitude gravitational time-dilation approximation, that predicts a clock gain on the order of a few dozen nanoseconds over the duration of the stay.
The measured result was about 22 nanoseconds.
The interesting part is not that this replaced laboratory relativity experiments. It did not.
The interesting part is that precision equipment had become accessible enough for an obsessive hobbyist to turn one of physics’ strangest effects into a family-scale experiment.
The accompanying web material preserves the whole spirit of it: hardware, clocks, travel, photographs, calculations, and the slightly deranged confidence required to bring cesium standards on a road trip because altitude changes time.
Later discussions in the timekeeping community kept pointing back to the experiment precisely because it makes an abstract result tangible.
Nobody has to imagine a spaceship moving near light speed.
You can drive uphill.
CacheRat’s 1,967 Ancient Web Domains research list includes experiment pages like this because the old web was unusually good at preserving the entire notebook around a weird personal project—not only the final result.
A family went camping.
The clocks came back older than expected.
By about twenty-two billionths of a second.