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Turning Stopwatches into Tricorders
how close are we to developing something like this?
I read a fascinating article last week on the state of atomic clocks. There's nothing more fun than rank scientific speculation, so let's have a go.
First we start with a little text from the article over on wired. It's about how small and precise atomic clocks are becoming
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.
"Each atom has its own spectral signature," says Hollberg. Calcium resonates to red, ytterbium to purple. At their most ambitious, NIST scientists hope to wring 10-18 out of a single trapped mercury ion with a chartreuse light -- slicing a second of time into a quadrillion pieces.
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.
Reading the environment from the relativistic effects that mass has? I might be wrong, but that sounds a lot like a "Star Trek" moment to me.
Aside from the cool stuff, which I'll get to in a minute, I'm fascinated that we're able to measure something with illuminating it with any kind of radition. Obviously this wouldn't work at the molecular level -- you can't measure something without changing it -- but even at the macro level it's wild. The team has already been playing around with some of this cool stuff.
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."
Picture an array of micro-sized super-precise atomic clocks, say in the shape of a cube. Make it a million clocks on each edge.
If I understand what I'm reading correctly, each clock would "read" the mass in the local environment in a different fashion. Seems like you could take a computer and create 3-dimensional images from this array. Such an image should be able to create a map of the local environment and even predict the masses of the things in the map. Track moving organisms? Most likely. Resolve down to the level of say a cubic millimeter or so? Maybe.
So hook this rascal up to a set of glasses. Bingo. You can see in the dark, behind walls, through clothes and armor -- just about anywhere. How about a medical diagnostic device where it can scan a patient's body and report back on what is going -- all without using any kind of x-rays or sound?
Any way you slice it, if this stuff takes off we're seeing a huge change in technology. This probably has my vote as the most interesting science article of the last year. They're talking about the initial applications with one sensor coming in just a few years. So within twenty or thirty years we should see the really wild stuff. I can't wait.
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