Hours away from any airport, deep in the heart of the Sierra Diablo mountains along the Texas-Mexico border, a 500-foot-tall clock is taking shape. In an era when atomic clocks can tick billions of times a second, the colossal timepiece will tick once a year — for the next 10,000 years.

The 10,000 Year Clock is the brainchild of inventor Danny Hillis, who dreamed up the idea in 1986 as a way to encourage people to think about humanity’s distant future. After spending a decade designing the clock, Hillis and the San Francisco-based Long Now Foundation he co-founded are building and installing it within a mountain owned by Amazon and Blue Origin founder Jeff Bezos, who has invested $42 million in the project.

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Last week Bezos tweeted a time-lapse video showing construction of the clock, calling it “a symbol for long-term thinking.”

Installation has begun—500 ft tall, all mechanical, powered by day/night thermal cycles, synchronized at solar noon, a symbol for long-term thinking—the #10000YearClock is coming together thx to the genius of Danny Hillis, Zander Rose & the whole Clock team! Enjoy the video. pic.twitter.com/FYIyaUIbdJ — Jeff Bezos (@JeffBezos) February 20, 2018

The foundation’s website offers its own rationale for building the clock via a series of questions: “If you have a Clock ticking for 10,000 years what kinds of generational-scale projects will it suggest? If a Clock can keep going for ten millennia, shouldn’t we make sure our civilization does as well? If the Clock keeps going after we are personally long dead, why not attempt other projects that will request future generations to finish?”

The clock will be driven by giant gears within a shaft in the mountain and powered by thermal energy harvested from the changes in temperature associated with the day/night cycle on the mountain above. The clock can also be wound by people who make the difficult hike to the site for a visit.

The first prototype of the 10,000 Year Clock. The Long Now Foundation

A century hand will advance once every 100 years, and a cuckoo will emerge once every 1,000 years, according to a blog post by Bezos. The mechanism will also contain 10 bells and a so-called “melody generator,” created by rock musician Brian Eno, that is designed to produce a unique pattern of chimes each time the bells sound.

No completion date for the clock has been set. But already it’s captured the imagination of many people, including Lee Smolin, a theoretical physicist and the author of “Time Reborn: From the Crisis in Physics to the Future of the Universe.” As he told NBC News MACH in an email, “The clock of the Long Now impels us to wonder how we will live as far in the future as we are from the beginnings of cities, far beyond the spans it will take to solve all the problems that occupy our thoughts now… If the clock can be built, it may inspire the imaginations of billions of people."

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