The Great Space Race ... With Clocks

Summary

Short Wave Podcast Summary: "The Great Space Race ... With Clocks"

Release Date: May 26, 2025

Hosts: Emily Kwong and Regina Barber
Guest: Holly Leopardi, Atomic Physicist at NASA's Goddard Space Flight Center

---

1. Introduction: Time as a Navigational Tool

Emily Kwong and Regina Barber kick off the episode by drawing parallels between the historical challenges of determining longitude at sea and the contemporary hurdles faced in space exploration. They emphasize the fundamental role of precise timekeeping in navigation, both on Earth and in the vastness of space.

---

2. The Longitude Problem: A Historical Perspective

[00:28 - 02:17]

The hosts delve into the 1600s dilemma of calculating longitude, a critical factor for determining a ship's east-west position. Regina explains, "Longitude is like the east-west position on Earth. It's relative to the prime meridian in Greenwich, England, right?" (00:34).

Emily elaborates on the complexity of maintaining accurate time at sea:
"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." (01:03).

Clock Drift and Its Dangers:
The rudimentary clocks of the era were susceptible to "clock drift" due to the harsh maritime environment, leading to navigational errors. Emily highlights, "Clock drift is dangerous. Regularly throughout the 16 and 1700s, this accumulation of errors threw ships so off course that it resulted in shipwrecks and lost lives." (01:32).

---

3. The Marine Chronometer and Its Impact

[01:58 - 02:46]

In response to the dire need for accurate timekeeping, the British government established the Board of Longitude, which initiated a contest to solve the longitude problem. The outcome was the development of the marine chronometer, a highly precise timekeeping device.

Regina summarizes the chronometer's significance:
"Fewer shipwrecks. Because now, like, ships knew the time and knowing the time let them know where they were." (02:10).

Emily adds, "This really made seafaring possible for the British Empire. So this clock changed world history." (02:17).

---

4. The Modern Parallel: Space Exploration and Precision Timekeeping

[02:31 - 04:29]

Drawing a connection between past maritime challenges and today's space endeavors, the hosts note that precise timekeeping is equally crucial for navigating space. Emily states, "The hurdles that were kicking around during the era of the longitude problem are repeating themselves today." (02:35).

Regina emphasizes the ambitious scope of current space missions:
"We're planning to go to Mars, maybe even further into space." (02:31).

Emily underscores the essential role of advanced clocks in space navigation:
"To navigate far from home, you need a really good clock." (02:46).

---

5. NASA's Quest Lab and the Development of OASIC

[04:29 - 08:17]

The narrative transitions to NASA's Goddard Space Flight Center, where the Quest Lab is at the forefront of developing next-generation atomic clocks. The hosts describe their visit, highlighting the collaborative environment of the lab.

Introducing Holly Leopardi:
Holly, an atomic physicist, explains the lab’s mission:
"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." (04:35).

Lab Environment:
Emily and Regina provide a vivid depiction of the Quest Lab's setup, emphasizing the precision and durability required for space-bound technologies.

Renee Reynolds' Vision:
Assistant Chief for Technology, Renee Reynolds, articulates NASA's strategic direction:
"We do see quantum technology as a path to be able to move beyond some of our classical techniques that may be reaching their limits." (05:42).

---

6. Understanding Atomic Clocks

[08:37 - 11:37]

Emily undertakes the task of demystifying atomic clocks, likening them to intricate feedback systems. She breaks down the components:

• Oscillator:
  "Like a pendulum, which swings back and forth once per second. In modern clocks, their pendulum is actually a crystal of quartz." (09:02)

• Reference:
  "An atomic clock is called that because it uses part of an atom as its reference." (09:33)

Regina contributes by explaining atomic transitions using hydrogen as an example, making the concept accessible:
"If an atom absorbs energy... the electron will change its orbit... when the electron eventually goes down, energy is released from that atom as another photon." (09:56).

Holly introduces the OASIC (Optical Atomic Strontium Ion Clock), emphasizing its enhanced precision:
"Instead of going from shining microwave light on the atoms, we can go shine optical light or use lasers on the atoms. We can get to 10 to the minus 17, 10 to the minus 18, and even 10 to the minus 19." (11:37).

---

7. The Promise of OASIC and Future Implications

[11:37 - 15:09]

Enhanced Precision:
Emily explains the advantage of using optical light over microwaves, allowing for unprecedented precision that minimizes clock drift:
"The laser being precise makes the strontium atom precise, which makes the clock precise." (12:08).

Holly discusses the broader applications of these ultra-precise clocks:
"So my goal is to have a clock network in space, especially an optical clock network... you can start doing really cool fundamental physics." (13:37).

Scientific Breakthroughs:
Potential scientific advancements include:

• Monitoring Earth's gravitational field changes to track environmental shifts like melting sea ice and groundwater flow.
• Exploring the interaction between gravity and quantum mechanics, a central question in modern physics.
• Investigating dark matter interactions.

Peter Brereton reinforces the transformative power of quantum technology:
"This is the power of quantum technology, of systems that use the physics of atoms to be more accurate than systems using, like, classical physics." (12:27).

Timeline and Collaboration:
Holly outlines the project's ambitious timeline:
"The team wants a prototype system done by fall 2025, and she hopes OASIC could fly within six years." (14:33).

She also stresses the collaborative nature of the endeavor:
"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 in my lab." (14:48).

---

8. Conclusion

The hosts wrap up by reflecting on the significance of atomic clocks both historically and in the future of space exploration. They express admiration for the intricate science behind timekeeping and its profound impact on our understanding and navigation of the world and beyond.

Regina Barber:
"This was a great story. I loved it. I love learning about atomic clocks. Thank you for bringing it to us." (15:09)

Emily Kwong:
"It's always time for physics, Gina." (15:14)

They also give a shout-out to Deva Sobel’s book "Longitude" for listeners interested in deeper exploration of the topic.

---

Notable Quotes

• Regina Barber:
  "Longitude is like the east-west position on Earth. It's relative to the prime meridian in Greenwich, England, right?" (00:34)

• Emily Kwong:
  "Clock drift is dangerous. Regularly throughout the 16 and 1700s, this accumulation of errors threw ships so off course that it resulted in shipwrecks and lost lives." (01:32)

• Holly Leopardi:
  "So my goal is to have a clock network in space, especially an optical clock network... you can start doing really cool fundamental physics." (13:37)

• Emily Kwong:
  "The laser being precise makes the strontium atom precise, which makes the clock precise." (12:08)

• Regina Barber:
  "We are obsessed with acronyms." (04:58)

---

Key Takeaways

• Historical Significance: Accurate timekeeping was pivotal in solving the longitude problem, transforming navigation and enabling the expansion of empires.

• Modern Challenges: Space exploration demands even more precise timekeeping to navigate and conduct scientific research beyond Earth.

• Technological Advancements: NASA’s Quest Lab is spearheading the development of the OASIC, an optical atomic clock with unparalleled precision, promising significant advancements in both navigation and fundamental physics.

• Future Implications: Enhanced atomic clocks could revolutionize our understanding of the universe, from monitoring environmental changes on Earth to unraveling the mysteries of dark matter and the interplay between gravity and quantum mechanics.

---

Discover More:
For those intrigued by the intricate world of timekeeping and its impact on science and navigation, Deva Sobel’s book "Longitude" is highly recommended.

---

This summary was crafted to provide an in-depth overview of the "The Great Space Race ... With Clocks" episode of NPR's Short Wave podcast, ensuring that listeners gain a comprehensive understanding of the discussions without needing to listen to the full episode.

Transcript

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[Emily Kwong]

You're listening to Short Wave from NPR.

[Regina Barber]

Hey, everyone. Regina Barber here with Emily Kwong. And a story about time.

[Emily Kwong]

Yes, a tale about how time tells us our places in the world. So, Gina, are you familiar with longitude?

[Regina Barber]

Yeah. So longitude is like the east west position on Earth. It's relative to the prime meridian in Greenwich, England, right?

[Emily Kwong]

Yeah. The longitude there is 0 degrees and extends by 180 degrees westward and 180 degrees eastward. And back in the 1600s, it was really difficult to calculate longitude. 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.

[Regina Barber]

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.

[Emily Kwong]

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.

[Regina Barber]

Ooh, I like that term, clock drift.

[Emily Kwong]

Yeah. Clock drift is dangerous. Regularly throughout the 16 and 1700s, this accumulation of errors threw ships so off course that it resulted in shipwrecks and lost lives. And merchants and seamen began calling for a scientific solution. So the British government created the Board of Longitude, and they announced a contest to solve this problem, the longitude problem.

[Regina Barber]

Okay.

[Emily Kwong]

And out of that contest came the marine chronometer, a near frictionless pendulum that doesn't need to be reset as often and was therefore more precise.

[Regina Barber]

Right. So fewer shipwrecks. Because now, like, ships knew the time and knowing the time let them know where they were.

[Emily Kwong]

Yes.

[Regina Barber]

Okay.

[Emily Kwong]

This really made seafaring possible for the British Empire. So this clock changed world history. And I think history is repeating itself right now because many governments and companies are setting their sights on space exploration.

[Regina Barber]

Right. I mean, so we're planning to go to Mars, maybe even further into space.

[Emily Kwong]

Yeah. And the hurdles that were kicking around during the era of the longitude problem are repeating themselves today. To navigate far from home, you need a really good clock.

[Regina Barber]

That's why today on the show, space clocks how scientists are pushing the envelope to build an atomic clock with even better precision and what that could mean for addressing some of the Biggest mysteries of the universe. You're listening to Shortwave, the science podcast from npr.

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[Regina Barber]

All right, Em, you ventured actually a few miles north in D.C. to NASA's Goddard Space Flight center, which we've been to together, and it's like, super cool.

[Emily Kwong]

Yeah. Goddard is a campus. 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.

[Holly Leopardi]

So this is building 33. We're gonna walk into the Quest Lab.

[Emily Kwong]

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.

[Holly Leopardi]

Yep.

[Regina Barber]

I mean, that's a good acronym. Like physicists and astronomers. Like we are obsessed with acronyms.

[Emily Kwong]

Yes, I've noticed. Okay, 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.

[Holly Leopardi]

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.

[Regina Barber]

Okay. I loved optical benches when I was like a physics undergrad and I was always the student that screwed in the beam splitters and the mirrors.

[Emily Kwong]

Of course you were. And not only is the precise alignment important, but the system has to be really durable.

[Regina Barber]

Right.

[Emily Kwong]

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 Assistant Chief for technology Renee Reynolds has been at NASA for 25 years. And in the last few years, she's really been the person to build up the quantum program and hire scientists like Holly. We do see quantum technology as a path to be able to move beyond some of our classical techniques that may be reaching their limits. And one piece of technology that NASA wants to improve is the atomic clock. They want to build new atomic clocks for space.

[Regina Barber]

Right. So tell me about the atomic clocks that are like in space, orbiting, like.

[Emily Kwong]

Right now there are hundreds. Many of them are perched on navigation satellites. I had no idea. Actually, like, navigation uses time. It's just like in the 1600s. But here in the US you know, our satellite based navigation system is GPS.

[Holly Leopardi]

Each satellite emits a timing signal and you receive those timing signals on your GPS receiver on your phone, and from those timing signals, it triangulates where you are.

[Emily Kwong]

So GPS is kind of like a clock.

[Holly Leopardi]

GPS is all clocks. And so if we have better clocks on gps, we would know our location to higher degrees of accuracy. Gps, Internet timing protocol, stock trading, all of these things rely on more accurate systems.

[Emily Kwong]

But the atomic clock system, as it stands right now, is error prone. Yeah, GPS clocks are estimated to drift by about 10 nanoseconds a day, which I know doesn't sound like a lot, but an error of even a microsecond in space can translate to an error of 300 meters on the ground.

[Regina Barber]

Right.

[Emily Kwong]

So to correct for clock drift, GPS clocks will send the signal a few times a day down to Earth and ask, you know, hey, am I on time?

[Holly Leopardi]

And then the Earth says, okay, your clock is. This has accumulated this much error. It's this much seconds off or time off, and then they send another signal back.

[Emily Kwong]

But this process is kind of a pain, you know, this constant, like phoning home. So for years now, NASA has been searching for a clock that is capable of autonomous navigation, able to operate as its own unit with minimal updates and be even more precise. All of this reminds me of what the Board of Longitude was trying to do all those centuries ago. Holly, she calls her clock.

[Holly Leopardi]

Oasic Optical atomic strontium ion clock.

[Regina Barber]

Oasic. It's a cover. It's a Science Oasis cover band.

[Emily Kwong]

I'm going to explain why oasic holds such promise, what all those different words in that sentence mean. But I need to call upon the spirit of my grandfather Bob, who was a clock repairman, and first explain how an atomic clock works.

[Regina Barber]

Works. As a physicist, I still, like, struggle with this. So let's do it.

[Emily Kwong]

It's like the Mr. Potato Head of science. You have to smash so much tech together to make it go. So all you need to know about a clock, this is true of all clocks, is they are feedback loops, and there's generally three elements that talk internally to each other within the clock to keep it steadily ticking. The first part is an oscillator, which.

[Holly Leopardi]

Is something that swings back and forth.

[Emily Kwong]

Like a pendulum, which swings back and forth once per second. In modern clocks, their pendulum is actually a crystal of quartz. That's so cool. When jolted with electricity, the quartz will vibrate at a precise frequency and emit electrical pulses, which can then be measured.

[Holly Leopardi]

By a counter which counts up those swings, those cycles, and displays them.

[Regina Barber]

Okay, so you got your oscillator, you got your counter. What's the third thing that makes it a clock?

[Emily Kwong]

Your reference. So the reference ensures that the oscillator vibrates at the right frequency and doesn't cause the clock to drift. And that's where the atoms come in. An atomic clock is called that because it uses part of an atom as its reference. Atoms have this really special quality, and I'm going to turn it over to you now, Gina, to explain how atoms go from a grounded state to an excited state.

[Regina Barber]

Yeah. So most atomic clocks use an atom of cesium or rubidium. But in general, I think it's, like, easiest to explain this process with, like, the element hydrogen, because it just has one proton at its center and one electron orbiting it. And, like, orbit is a bit of a simplification for now, but let's just say orbit electrons, they have these different orbits. Each of them are associated with, like, a different energy. And if an atom absorbs energy, let's say through like, a little chunk of light or a photon, the electron will. Will change its orbit. It'll go to, like, this higher energy state. It'll go to a higher orbit, and then when the electron eventually goes down, energy is released from that atom as another photon.

[Emily Kwong]

Okay. So that in the 1950s, scientists hacked this particular ability of an atom and forced this energy transition in the atom at a regular interval and designed a clock that would count every time energy is released as the electron goes back down. And that is the frequency of the atomic clock.

[Regina Barber]

Okay. And they did this with light, Right?

[Emily Kwong]

Right. So traditional atomic clocks, the ones used for gps, use microwaves, which is a form of light. How the clock works is it bombards an atom with microwaves, and that forces the atom from its grounded state to its excited state. And that transition happens at a steady pulse by which the whole clock is referenced.

[Holly Leopardi]

But those clocks are accurate to the 10 to the minus. The best ones are 10 minus 16.

[Emily Kwong]

Which is not good enough for. For Holly as an atomic physicist. I know, but microwave is not precise enough for her. She and other atomic physicists work with optical light. Optical light has a shorter wavelength, so it's a better light source by which to control an atom.

[Holly Leopardi]

Instead of going from shining microwave light on the atoms, we can go shine optical light or use lasers on the atoms. We can get to 10 to the minus 17, 10 to the minus 18, and even 10 to the minus 19. So these are, you know, up to three orders of magnitude improved over current microwave clocks.

[Emily Kwong]

That level of precision means the clock should be better at staying on time without needing to dial earth nearly as much for a time check.

[Regina Barber]

And it's more precise because it's using optical light instead of microwaves.

[Emily Kwong]

Yes. And because the clock is powered by a strontium atom.

[Regina Barber]

Ooh, I don't know anything about strontium.

[Emily Kwong]

Strontium. It's a weird. It's like in the periodic table. No one talks about it, But Holly chose strontium because it's good at withstanding standing temperature swings, good for space. And also castrantium requires a very precise frequency to get excited.

[Regina Barber]

Oh.

[Emily Kwong]

So she. She told me to think of the laser like a drum beat. Boom, boom, boom. But the atom is like a conductor. And if you've ever seen an orchestra, you know, a conductor will only tolerate the correct drum beat. Strontium is a very strict conductor.

[Regina Barber]

Okay. So like in this case, the atom will only get excited if the laser is on beat. It has that specific frequency. Yes.

[Emily Kwong]

The laser being precise makes the strontium atom precise, which makes the clock precise. Peter Brereton, who runs the lab, says this is the power of quantum technology, of systems that use the physics of atoms to be more accurate than systems using, like, classical physics.

[Regina Barber]

Her clock is referenced to an atom, and an atom here is the same as an atom on Mars. And so that long term stability, that reference inherently can't change. And so what will Oasic the clock look like once it's built?

[Emily Kwong]

Like the tesseract in the Marvel movies.

[Regina Barber]

Really?

[Emily Kwong]

It'll be a blow. No, it will be a cube, though. It will be a cube with all these optical systems bolted into place and a single strontium atom at its core. And I asked Holly what she ultimately hopes for these clocks, where she wants them to live.

[Holly Leopardi]

So my goal is to have a clock network in space, especially an optical clock network, because when you start getting down to the 17th, 18th, 19th and beyond level of precision, digit of precision, you can start doing really cool fundamental physics.

[Emily Kwong]

So if multiple OASIS clocks get installed up in space, scientists can compare how their frequencies change, 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.

[Holly Leopardi]

And you could start looking for how does gravitation and quantum mechanics interact? Can we understand dark matter interactions? Things like that.

[Emily Kwong]

Wow.

[Regina Barber]

Okay. So gravity and quantum mechanics interacting is like the holy grail of physics. Okay, so how far along are these new clocks?

[Emily Kwong]

Holly says the team wants a prototype system done by fall 2025, and she hopes OASIC could fly within six years.

[Regina Barber]

Okay.

[Emily Kwong]

She is determined to do this for timekeeping and also for the field of physics.

[Holly Leopardi]

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 in my.

[Emily Kwong]

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.

[Regina Barber]

This was a great story. I loved it. I love learning about atomic clocks. Thank you for bringing it to us.

[Emily Kwong]

It's always time for physics, Gina.

[Regina Barber]

It's always time for physics. Always.

[Emily Kwong]

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.

[Regina Barber]

This episode was produced by Hanna Chin. It was edited by showrunner Rebecca Ramirez. And Tyler Jones checked the facts. Jimmy Keeley was the audio engineer.

[Emily Kwong]

Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy.

[Regina Barber]

I'm Regina Barber.

[Emily Kwong]

And I'm Emily Kwong. Thank you, as always, for listening to shortwave, the science podcast podcast from npr.

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