It's Memorial Day, Short Wavers. This holiday, we bring you a meditation on time ... and clocks. There are hundreds of atomic clocks in orbit right now, perched on satellites all over Earth. We depend on them for GPS location, Internet timing, stock trading and even space navigation. In today's encore episode, hosts Emily Kwong and Regina G. Barber learn how to build a better clock. In order to do that, they ask: How do atomic clocks really work, anyway? What makes a clock precise? And how could that process be improved for even greater accuracy?- For more about Holly's Optical Atomic Strontium Ion Clock, check out the OASIC project on NASA's website.- For more about the Longitude Problem, check out Dava Sobel's book, Longitude. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Have questions or story ideas? Let us know by emailing [email protected]!Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What is the Great Space Race about?
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Hey, everyone. Regina Barber here with Emily Kwong and a story about time. Yes.
A tale about how time tells us our place in the world. So, Gina, are you familiar with longitude?
Yeah. So longitude is like the east-west position on Earth. It's relative to the Prime Meridian in Greenwich, England, right?
Yeah. The longitude there is zero degrees and extends by 180 degrees westward and 180 degrees eastward. And back in the 1600s, it was really difficult to calculate longitude. Right. a ship leaving port would set two clocks, one for the prime meridian and another for local time. So crews would update their local time as they sailed, calculating it by using the position of the sun.
And by knowing the difference between these two times, you can calculate, like, the in-between longitudinal degrees and know your location. Yeah, you can math. Right.
But the clocks aboard these ships were not reliable. Like, picture pendulum clocks on rolling seas, right? Surrounded by salty air and changes in temperature or barometric pressure. The clock parts are going to warp. All of this can ultimately cause the clock to stray from the correct time. We call this clock drift. Ooh, I like that term, clock drift. Yeah, clock drift is dangerous.
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Chapter 2: How did longitude affect navigation in the past?
They have a soccer league, a theater club that performs shows. But I was on shortwave duty, so I went there to see a lab. Cool.
So this is Building 33. We're going to walk into the quest lab.
with Holly Leopardi, an atomic physicist with green glasses and a big grin. And two years ago, she was telling me she joined the Quest Lab. The Quest Lab is like a one-stop shop for atomic physicists to do experiments and pass along those discoveries to NASA engineers. Quantum engineering and sensing technologies. Quest. Were you like, yes, we made an acronym?
Yep. I mean, that's a good acronym. Like physicists and astronomers, like we're obsessed with acronyms.
Yes, I've noticed. OK, so the main lab of Quest is a big room with three massive tables. The tables are made of metal and they have holes in them drilled every inch on like the surface of the table. And that's to screw down different optical components.
Kind of the classic first mistake that, you know, when you walk into an undergraduate physics lab is they make a nice aligned optical system and they don't screw the mirrors and things down on the table and then they move.
Okay, I loved optical benches when I was like a physics undergrad and I was always the student that screwed in the beam splitters in the mirrors. Of course you were. And not only is the precise alignment important, but the system has to be really durable.
Right. Whatever is invented here has to survive being jettisoned into space.
We're not developing technologies for them to sit on a shelf somewhere. We want to actually fly them in space and we want them to make a difference for our science measurements.
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Chapter 3: What is clock drift and why is it important?
So if multiple OASIC clocks get installed up in space, scientists can compare how their frequencies change relative to each other. And this data will allow them to tackle some big questions like changes to Earth's gravitational field, which could tell us how sea ice is melting or groundwater is flowing.
And you could start looking for how does gravitation and quantum mechanics interact? Can we understand dark matter interactions, things like that?
Wow. OK, so gravity and quantum mechanics interacting is like the holy grail of physics. OK, so how far along are these new clocks?
Holly says the team wants a prototype system done by fall 2025, and she hopes OASIC could fly within six years. Okay. She is determined to do this for timekeeping and also for the field of physics.
The field wants this, and it would take a lot of academics, a lot of companies, a lot of even nations to make this happen. It's bigger than just me and my lab.
Because for her, a clock's real power is as a sensor to tell us where we are and how the universe is changing around us.
This was a great story. I loved it. I love learning about atomic clocks. Thank you for bringing it to us. It's always time for physics, Gina. It's always time for physics.
Always. Special thanks to Deva Sobel, who wrote the incredible book Longitude, all about the longitude problem and the creation of the marine chronometer. It's a great read.
Check it out. This episode was produced by Hannah Chin. It was edited by showrunner Rebecca Ramirez and Tyler Jones checked the facts. Jimmy Keeley was the audio engineer.
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