If humans ever expect to live on Mars, we’re going to need to get very good at keeping Martian time. The task is simple enough on Earth, thanks to standardized time zones based on a single planet’s daily rotation. But scheduling a long-distance chat between different planets won’t be as easy. While NASA will undoubtedly rely on advancing computing tools and laser communications arrays, you don’t need particularly high-tech equipment to learn the approximate time on a neighboring planet. As a U.K.-based team of DIY specialists at Chronova Engineering recently showcased, all that’s needed is a few well-designed (and well-placed) gears.
Building an Interplanetary Clock
Okay, maybe that’s a bit of an understatement. Chronova’s Interplanetary Clock is as beautiful as it is mechanically imposing. According to their construction documentary, the device requires 131 individual parts, including bespoke-cut gears placed in seven gear trains to interpolate between not only Earth and Mars, but also Jupiter and Saturn. Each planet’s dial shows what it looks like as seen from its north pole and displays longitude with 0-degrees representing the planet’s prime meridian. Three pointers are then placed around the dials to signify which longitudes are currently experiencing sunrise, noon, and sunset. As an extra flourish, all four celestial bodies feature a polished, color-coded stone.
While a single day on Earth lasts 24 hours, this isn’t the case for other planets with vastly different sizes, rotational speeds, and orbital distances. If every disk represents one day, then how do you calculate the number of gear teeth for each respective planet?
“Mathematically, gears are very interesting,” the video’s narrator explains. “Because if you’re clever about it, it’s possible to accurately reflect relationships we observe all around us with a surprisingly small set of gears.”
He offers Jupiter and Mars as an example. Jupiter completes 2.5 times rotations for every one spin of Mars, so the Red Planet gear receives 2.5 times as many teeth as Jupiter’s gear. That said, it’s much easier to observe a rocky planet’s rotation, but determining a central reference point becomes a bit more complicated for gas giants like Jupiter and Saturn. For this project, the creators opted to settle on what’s known as the System 3 reference frame. This type of frame uses a gaseous planet’s magnetosphere as the basis for reflecting its core rotation.
The final result is mesmerizing, informative, and simply gorgeous to watch in action. It’s not so much a traditional clock as it is a measuring tool, but it’s all that’s needed to do some basic, interplanetary calculations
As an example, the team suggests a scenario in which a settlement established near NASA’s Perseverance rover wants to chat with Earth around the time of their Martian sunset. The first step would be to rotate the entire clock until the accompanying numerical Earth counter displays the number of days that have hypothetically elapsed since January 1st. Perseverance is located near 77 degrees longitude on Mars, so a user would then turn the crank until the sunset pointer is aimed at the correct longitude. Finally, you simply look at the Earth gear to get a sense of when to phone Mars. Unfortunately for folks at Chronova Engineering, that would mean ringing the Red Planet in the middle of the night.
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