Atomic clock

If you want precise time, there's a really great app that I use because we synchronize with Kelowna's AM1150 and just for other things there.

I use an app called Atomic Clock on my iPhone, and you can change it whether you want it to be analog or digital.

I just use the free version there, so I get limited options there.

Okay.

So you will hear that coming up when we get to the top of the hour.

If you're listening on the podcast or on Sunday, we might be a few seconds off.

So again, it's called Atomic Clock Free on the Apple App Store.

And here's what happens at the top of the hour.

Well, I think there are applications that depend on what's called UT1, which is the angle of the Earth with respect to the stars.

And there was a lot of concern about a divergence between atomic time and UT1.

The leap second business was essentially to try to keep them within one second.

But there was some concern that you shouldn't abandon the link altogether.

The second thing is that the leap second introduced a discontinuity in time interval because there was this extra second which was added into the time, but real-time processes like navigation didn't stop.

And so when you wanted to measure the elapsed time, which was how you measure distance when measuring the elapsed time, you got into trouble because of this leap second business.

But the real trigger was the concern that there would be a negative leap second, that the Earth was speeding up, and that instead of atomic time being ahead of the Earth, the Earth might be ahead of atomic time, and that the negative leap second had never been done before, never been used before.

And so there were concerns that that would be a problem.

It was only in the late 19th century that time was standardized globally and that Greenwich was chosen as the location of the prime meridian.

The history of the measurement of time is a long one, from earlier man tracing his days from sunrise to sunset, to the advent of atomic clocks in the 1950s.

We've constantly striven to calculate and control the time, but how did mechanisms for measuring time develop into such precise machines? And how did the changes in society drive the need for such precise timekeeping? With me to discuss the history of the measurement of time are Kristen Lippincott, former director of the Royal Observatory, Greenwich; Jim Bennett, director of the Museum of the History of Science at the University of Oxford; and Jonathan Betts, senior curator of horology at the Royal Observatory, Greenwich.

Kristen Lippincott, how did early, earliest civilizations measure using the natural phenomenon, measure time?

That's right.

This was a sort of refinement of quartz, really.

Uh, uh, atomic clocks actually have as their time standard a quartz clock.

Uh, what, i- i- in simple terms, w- what an atomic clock does is to kind of fine-tune the quartz and, um, watch how that quartz is behaving, and it uses atomic technology to kind of check how the quartz is, uh, how the frequency of the quartz is running.

I read the summary, but I really need you to explain the mechanics of how this actually worked.

So physicists Joseph Hafele and Richard Keating took four cesium atomic clocks and put them on commercial jet planes.

Let's break down the mechanics first.

An atomic clock doesn't use gears or pendulums, you know.

And then they just bought them plane tickets?

Yes.

They literally strapped these highly sensitive atomic clocks into the first class seats of commercial Pan Am flights.

That's hilarious to picture.