John Patterson is a humble watchmaker in Kauai, Hawaii, who, for the past five years, has been quietly making the world’s first consumer-level atomic watch. Let a thousand years pass and this watch will only lose a second in accuracy. Take it deep underwater, inside an inferno: Time keeps ticking. Or, if you’re feeling adventurous, take it to space. Take it to Mars.

It will keep time.

Patterson has a Ph.D. in neuroscience, but he’s poured his own brainpower into watchmaking. He runs his company, Bathys Hawaii, from his house on the Garden Isle. “The philosophy was always that it wasn’t just a rich guy who deserved to have a nice watch,” he tells Inverse. Bathys comes from the Greek word “bathus,” which means “deep” — literally and figuratively. While his watches will stay true at great depths, his atomic watch will stay true at great heights, too. Mars heights.

A $200 million Defense Advanced Research Projects Agency grant led to the creation of the small atomic chip inside the Bathys Hawaii Cesium 133, Patterson explains. But once he discovered that the chips were available for purchase, he grabbed an “old OMEGA watch” that he had stowed away in a drawer, sold it on eBay, bought an atomic chip, and — with the help of one or two other Hawaiians — got to work.

He knew he had to use the atomic chips for their truest calling: watches. The international second, after all, is defined by cesium: Its radiation frequency is 9,192,631,770 Hz, which scientists in the 1950s linked up to ephemeris time. Whereas other clocks fall victim to relativistic effects at high speeds, cesium clocks do not. The frequency remains the same, and so the time remains accurate. So Patterson, chip-in-hand, got to work. Soon, he had a functioning, incredibly accurate wristwatch; he took the prototype to Kickstarter in 2014. In just a few days, he had almost doubled his fundraising goal.

Inverse spoke with Patterson about the technology behind the Cesium 133 watch, about space travel, and about how soon we’ll all own atomic watches. (Hint: Soon. But they may not be watches, per se.)

How does the Cesium 133 work?

It’s pretty complex. Not only did we have to design the watch using this chip, a rechargeable battery, et cetera, but we also had to design an external base station–type thing that works to charge the watch. But, mainly, it works to set the watch as accurately as possible. These watches can be set to within less than 100 nanoseconds — that’s a hundred-billionth of a second — to the exact, international standard time for the globe. Once they’re set, they’re accurate to one second in a thousand years. The clock that’s on your phone, or computer — most are only accurate to about 200 milliseconds. That’s the error that this watch develops in 200 years.

The GPS is done! This pulls down an accurate time pulse to set the Cesium 133 within 20 billionths of a second.

A photo posted by Bathys Hawaii (@bathys_hawaii) on

We had to copy the same thing the military does when they want to set one of their atomic clocks. Even GPS receivers are off by several hundred milliseconds: The computer spends all its time processing the location data, and not the time. So we had to make our own GPS unit that basically focuses on just passing through the time data without any delay at all. It just sucks it out of space and sends it straight to the watch without any delay at all.

From what I understand, cesium watches are appealing not just because of their accuracy, but also because they hold their accuracy in many conditions.

Yup. Temperature is a big thing in timekeeping. So, you can go up to about 150 degrees Celsius or down to about minus 20 degrees Celsius, and it stays accurate.

Once you set this clock accurately, if you hook it up to the accelerometer, and the compass, and the internal inertial units in your phone — which basically record incline, acceleration, and all that stuff — it can act as its own GPS, without having to be in contact with GPS. It can accurately track your location down to 10 centimeters for days, for months.

There are so many possible technologies that could grow out of that. If you are a firefighter in New York City and have to rush into a burning skyscraper, you’re going to lose your GPS, so you’re not going to be able to communicate your position to other firefighters. But if everyone had synced up this watch, it could just talk over the regular radio frequencies, and it could tell them where they were. It doesn’t matter if they’re in a cave, in a burning building, or underwater: Anywhere you can’t get GPS, you can get your location.

Or space.

Or space. Or in a tunnel with your self-driving car.

Could this watch be something people who wanted to go to Mars could use to keep time?

First off, a little side note: I was actually on the shortlist to be in one of the Mars habitats. The one over here in Hawaii. I got through to the very final selection. They picked six, and I was in the final 30. I think I was too old, and I’m glad as hell that I didn’t get to do it. They just came out the other day, and now I’m like, ‘I’m so glad that’s not me.’ The guy’s kissing his wife for the first time in a year — I’m like, ‘Hell no.’

A regular watch would work in space to some degree. A quartz watch will keep time in space — it’s not like it’s not going to work at all. But there are relativistic effects of moving fast.

If your GPS doesn’t account for the travel time to the satellite, instead of being able to locate you within six or seven feet like your phone does right now, it goes out to 35 kilometers. That’s how important it is that the relativistic effect is taken into account. The speed of light and the speed of the satellite is so fast that it slightly changes time.

It’s really easy to explain how the cesium works. Basically, the way to think about it is that the cesium is almost like a mirror. If you make it vibrate at the exact frequency of that nine billion cycles per second, it acts like a mirror. Whatever energy you shoot at it shoots back at you. At any other frequency, it’s like a black piece of velvet: It absorbs the energy. Right when it gets to that exact frequency, and you’re bombarding it with your microwave, all the sudden all your microwaves start bouncing back. And that means you nailed it.

That’s a physical characteristic of cesium. It has nothing to do with radioactive anything. Cesium is like mercury, almost — it’s a liquid. When you heat it up, it turns to a gas. Inside the little cell, there’s a little heater that heats the gas up, bombards it with radio waves, and looks for this reflection. The actual international standard for one second is that number of vibrations.

That never changes: You go to space, that’s the same. You go close to the speed of light — doesn’t change. Whereas if you took a quartz watch, or a mechanical watch, and started taking it to super-fast speeds, it would cause things to change, and it wouldn’t be accurate anymore.

Will these chips find their way into other technologies soon?

I think you’ll see this technology in your smartphones and in your self-driving cars in about five years. It will probably be more like the GPS that appears in your phone. All the sudden you’ll see this technology miniaturized to the point where it could fit in a phone. Right now, the chip is the size of a matchbox from a fancy restaurant. It’s pretty big, and it can’t be made much smaller because of the physics packaging stuff that has to fit in there. But if they could miniaturize it yet one more level, then it would appear everywhere. The technology isn’t expensive to make — it could definitely be done. So I’d say five or six years, but I don’t really expect the Swiss to be the one. I expect more, like Samsung, or Apple, or Google to be the one.

This interview was edited for brevity and clarity.

Photos via Bathys Hawaii

Joe is a writer from Vermont who lives in Brooklyn. He has written for PopSci and McSweeney’s Internet Tendency and spent a year playing with words and other writers’ dreams at Tin House in Portland, Oregon.