Ticks of the atomic clock

Bern ClockI rely on my phone to keep track of time - I tend to lose/break or cover watches in chalk, but my phone is pretty reliable. But how does it know the time, and how to people keep track of the passing seconds? Find out in this month's SITN Flash.

Last month, the Flash was spintronics, but the latest is atomic clocks:

While atomic clocks are technologically more complicated than the average timepiece, their operating principle is more or less the same - time is kept by precisely measuring the frequency of a signal. Frequency expresses how often a periodic signal repeats itself. In a grandfather clock, the frequency refers to the number of times per second a pendulum swings back and forth as it mechanically drives the clock's hands; for a modern quartz watch, the frequency of interest is the number of electrically driven vibrations per second in a crystal, a signal that is converted into electronic pulses that are displayed digitally.

In contrast with conventional clocks, atomic clocks tune their ticks to the oscillations of atoms as they absorb particular frequencies of light.

There's also some great history on the standardization of world times. Give it a read - you won't regret it.

------

[image by me from my trip to Bern, Switzerland in 2008]

More like this

Over at A Blog Around the Clock, Bora put up a sixteen part series of posts talking about clocks. Unfortunately, he was talking about biological clocks, which are a specific and sort of messy application, from the standpoint of physics. I talk a bit about clocks for our first-year seminar class, as…
I was looking at some polling about science over the weekend, and discovered that they helpfully provide an online quiz consisting of the factual questions asked of the general public as part of the survey. Amusingly, one of them is actually more difficult to answer correctly if you know a lot…
This is nearly a month old, now, because I keep saying "Oh, Idon't have time to do this justice-- I'll write about it tomorrow." I really need to stop doing that. Anyway, Physics News Update has a story about a scheme to measure gravity using Bloch oscillations, based on a paper in Physical Review…
In yesterday's post, I outlined the history of clocks starting from the essential feature of any clock, namely the "tick." I ended by saying that the best clock you can possibly make is one based off the basic laws of quantum physics, using the energy separation between two energy levels in an atom…

It had never occurred to me before that I didn't know how atomic clocks work.

By Drivebyposter (not verified) on 05 Jan 2011 #permalink