I’m a complex and ironic sort of guy. Take my fascination with the concept of time which is something I think about fairly regularly in both the abstract and literal senses of the word. You’d think that someone, like me, who not only ponders time quite a bit, but also has a small collection of clocks, would be a very punctual person, but I’m not. I’m often either earlier than I need to be or later than I should be to any appointment I might have and which end of said scale I tend to lean towards is probably dependent on who’s making the assessment (my wife, for example, thinks that I am habitually late to everything). Yet the concept of time and its measurement captures my fascination like few other things and probably explains my love of shows such as Doctor Who.
Needless to say that means super-geeky science articles such as the one titled How Super-Precise Atomic Clocks Will Change the World in a Decade at Wired.com make me giddy just thinking about them:
These rooms are where NIST is testing a new way of tapping the precision time built into elements like calcium and ytterbium. Cesium clocks like NIST-F1 use lasers to slow a cloud of cesium atoms to a measurable state, then tune a microwave signal as close as possible to the cesium’s resonant frequency of 9,192,631,770 cycles per second (See sidebar: How the World’s Best Clock Works). In this manner, the F1 achieves a precision topping 10-15 parts per second.
At least, in theory. To tap the F1’s full accuracy, scientists have to know their precise relative position to the clock, and account for weather, altitude and other externalities. An optical cable that links the F1 to a lab at the University of Colorado, for example, can vary in length as much as 10 mm on a hot day—something that researchers need to continually track and take into account. At F1’s level of precision, even general relativity introduces problems; when technicians recently moved F1 from the third floor to the second, they had to re-tune the system to compensate for the 11-and-a-half foot drop in altitude.
Cesium, though, is a grandfather clock compared to the 456 trillion cycles per second of calcium, or the 518 trillion provided by an atom of ytterbium. Hollberg’s group is dedicated to tuning into these particles, which hold the key to a scary level of precision. Microwaves are too slow for this job—imagine trying to merge onto the Autobahn in a Model T—so Hollberg’s clocks use colored lasers instead.
Can you imagine that? A clock so accurate that you have to take into account where you are in relation to it and the environmental effects of where it’s located to make full use of it? The article points out that this is a level of precision that is generally not used by the vast majority of people who are just trying to make it to the airport on time or figure out when to take lunch. So why then are they trying to come up with clocks that are even more precise than cesium based ones? Because once you get that precise some really funky stuff starts happening that turns your clock into more than just a ridiculously precise timing mechanism:
At that level, clocks will be precise enough that they’ll have to correct for the relativistic effects of the shape of the earth, which changes every day in reaction to environmental factors. (Some of the research clocks already need to account for changes in the NIST building’s size on a hot day.) That’s where the work at the Time and Frequency Division begins to overlap with cosmology, astrophysics and space-time.
By looking at the things that upset clocks, it’s possible to map factors like magnetic fields and gravity variation. “Environmental conditions can make the ticking rate vary slightly,” says O’Brian.
That means passing a precise clock over different landscapes yields different gravity offsets, which could be used to map the presence of oil, liquid magma or water underground. NIST, in short, is building the first dowsing rod that works.
On a moving ship, such a clock would change rate with the shape of the ocean floor, and even the density of the earth beneath. On a volcano, it would change with the moving and vibrating of magma within. Scientists using maps of these variations could differentiate salt and freshwater, and perhaps eventually predict eruptions, earthquakes or other natural events from the variations in gravity under the surface of the planet.
How freakin’ cool is that? Using a clock to find oil and water or mapping the bottom of the oceans! Of course this will require atomic clocks small enough to carry around, but they’re working on that already as well:
At the University of Pittsburgh last fall, 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.
Since then, NIST has improved the same clock by an order of magnitude. An array of such clocks, used as magnetometers, could produce completely new kinds of imaging equipment for brains and hearts, packaged as luggable units selling for as little as a few hundred dollars apiece.
The same technique for looking inward works outward too. Electromagnetic fields are all around us, and change very slightly in response to our movements. A precise enough clock perturbed by these fields can give data on where things are and what’s moving. Like the mouse’s heart, a closely synced array could build a real-time continuous picture of the surroundings—an area of research called passive radar. You could passively visualize pedestrians on a sidewalk, O’Brian says, “from the microwaves of the Doppler shift of someone walking.”
This sort of science is just uber cool to me and I can’t get enough of it. It gets me all excited in a way few things can and causes Anne to shake her head at me in wonder of what the hell I’m going on about. Not that she’s alone. I tried sharing this with the guys here at work and they just blinked at me a couple of times and went back to jabbering about sports.