I was looking for articles about really accurate clocks (OK, I’m using ‘accurate’ colloquially) and came across this one from late 2007, about How Super-Precise Atomic Clocks Will Change the World in a Decade and I was just intrigued by some of the things I saw in there.

For example, there is an optical cable that connects a (very precise) clock at a NIST building in Boulder to a laboratory at the nearby University of Colorado. On a hot day the length of this cable grows by 11 mm (less than half an inch). Researchers must monitor the temperature along the cable run and account for the (very measurable) difference this makes. Light travels about 200,000 km/sec (124,274 miles/sec) in an optical cable, so in a nanosecond it travels about 200 mm (8 inches). This clock is so precise that on a hot day they can tell that the light in the optical cable takes .05 nanoseconds more to travel the entire length of the cable. That’s .000 000 000 05 seconds. That’s how precise their clock is.

Einstein had a theory about time, space and gravity. Moving clocks run slower than stationary clocks. Gravitational changes affect time. These effects have been measured. While this may be kinda interesting, is this knowledge really useful for anything?

They can put a very precise clock on a ship and detect changes in the depth of the ocean floor. A very precise clock can tell you when the density of the earth “underneath” it has changed, showing where there is an underground quantity of oil, magma, or water (and yes, they can tell the difference between salt- and fresh-water).

How about this then: At the University of Pittsburgh in the fall of 2007, researchers used a NIST-produced atomic clock the size of a grain of rice to map variations in the magnetic field of a mouse’s heartbeat. They placed the clock 2 mm away from the mouse’s chest, and watched as the mouse’s iron-rich blood threw off the clock’s ticking with every heartbeat.

Do you think there are people working to turn this technology into a medical diagnostic tool?