When it comes to horology of any sort, be it clocks or watches, greater accuracy is one of those things that has always been chased. To be sure, those early pocket watches wouldn’t be considered remotely accurate by today’s standards – but they were, indeed, more accurate than trying to tell the time by looking at the sun, or guessing how long it had been since the bells of the local church rang.
And even with as accurate as things are these days, there are scientists pushing further in this arena. Just recently, physicists created a clock that can measure down to 1018 of a second. As to why? Well, this allows for a clock that only loses a second every 31 billion years. Additionally, it allows it to sense (this, I’m not quite sure how) differences in height at an accuracy of around 1 cm. I’m sure there are quite a few fields that could make use of this.
As to how it’s done? Well, the folks at NIST created something that they call an “optical lattice clock”. They do this by bouncing a laser off of a mirror in such a way that they create a standing wave of light, that becomes a lattice wherein they trap ytterbium atoms. At least, that’s as far as I can understand it. If your grasp of physics is a bit better than mine, or you simply would like to read more, the full article can be found here.