We know that the universe is roughly 13.8 billion years old—give or take a few hundred million years. Which seems like a decently accurate reading. But a new pair of clocks, which can measure time at a 10^18 fractional level, makes our own measurements look like child's play. To have the same level of precision as these twin timepieces, we'd have to be able to specify the age of the known universe to within less than one second.
Tweaking an already wildly accurate method of telling time might seem a tad excessive. But a single second didn't just arise as an arbitrary measurement—it's based on an atom's frequency. And accurately measuring this doesn't come easy. Anything from a stray electric field to any movement of the atom whatsoever affects the measurement—small sources of error, sure, but error nonetheless.
To overcome these complications, Andrew Ludlow at the National Institute of Standards and Technology in Boulder and his team used something known as an "optical lattice clock." By bouncing a laser off a mirror, they're able "to create a standing wave of light which forms a lattice to trap atoms. This is a kind of eggbox in which the atoms sit." With the ytterbium atoms neatly trapped, the clock is free to zap them with a different laser and measure the electrons' frequencies. Leaving you with a clock that will only lose about one second avery 31 billion years. Not bad.
And their extreme sensitivity means that they can measure the gravitational redshift, a phenomenon in which time moves more slowly in stronger gravitational forces—meaning they can alert us to changes in height. But while current clocks can sense change mostly kilometre-wise, these new ones will be able to measure a shift in height even at around 1cm. So these new clocks are ready to go right to work, particularly in fields such as hydrology, geology, and climate change in general.
Ludlow and his team may already looking to the next advancement in time measurement, but for now, this opens the door to some major advancements in our understanding of the world around us. Now if only there were a wrist-friendly version. [MIT Technology Review]