There’s a popular myth that the Library of Alexandria—the center of intellectual life in antiquity—was destroyed in a great fire. According to this myth, a vast collection of books and scrolls was tragically lost to history during a battle, an event that set back the advancement of human knowledge by centuries. In truth, the library and its reputation was likely slowly degraded by budget cuts, and a substantial number of its books were likely moved to other libraries, not destroyed. Still, the persistence of this myth speaks to our deep-seated anxiety about a cataclysmic event destroying our collective knowledge and sending our species back to the dark ages.

Today, the distinction of being the world’s library arguably belongs to Wikipedia, the nonprofit encyclopedia that boasts tens of millions of articles written in nearly 300 languages. Like the Library of Alexandria, Wikipedia is also in a chronic state of budget crisis, but its total destruction still seems unimaginable. Wikipedia doesn’t exist in a discrete location but is spread across servers around the world, which makes it resistant to censorship or a massive fire. Moreover, locally copying the contents of Wikipedia is relatively trivial compared to the scribes copying the scrolls at Alexandria 2,000 years ago.

In short, it appears like the only way to totally destroy Wikipedia would be to destroy the world, or at least all the humans on it. As unlikely as this may sound, cataclysmic extinction events have happened before on Earth and will, in all likelihood, happen again. This is part of the reason why the Arch Mission Foundation, a nonprofit created by American serial entrepreneur Nova Spivak, is printing out all 25 million pages of the English version of Wikipedia and sending it to the moon. That way, even if humans don’t make it, a comprehensive record of our existence will survive for millennia.

Toward a cosmic library

The Arch Mission Foundation was founded by Spivak in 2016 with the goal of sending archives of human knowledge—housed in objects called Archs (pronounced “arks”)—into space. The project was inspired by Isaac Asimov’s Foundation trilogy, which tells the story of a group of academics and artists tasked with preserving humanity’s collective knowledge to mitigate an impending galactic dark age predicted to last for thousands of years.

Spivak’s original plan was to send a copy of the English version of Wikipedia into high earth orbit by piggybacking on a commercial geostationary satellite. This plan would eventually expand to include Archs placed in orbit around the moon and elsewhere in deep space. Spivak’s original timeline for launching the first Arch was before 2050 and by 2100 to have Archs distributed throughout the solar system.

Three copies of the quartz discs containing Asimov's 'Foundation' trilogy. One of these disks was launched on Musk's roadster earlier this year. Image: Arch Mission Foundation

Earlier this year, Spivak and his colleagues successfully launched their first Arch into a billion-year orbit around the Sun. The library hitched a ride on Elon Musk’s Tesla Roadster in February after Spivak caught Musk’s attention on Twitter. The Arch consisted of a quartz disk containing a copy of Isaac Asimov’s Foundation trilogy stored using a 5D optical technique developed by University of Southampton physicist Peter Kazansky.

Although similar quartz disks will eventually be able to store 360 terabytes of data, only a small portion of this was used to store the Foundation trilogy. The reason for this, Spivak told me over the phone, was that the process of writing the data to the disk was both incredibly expensive and time consuming. To send all of Wikipedia to the moon, he had to figure out a more efficient storage technique that is capable of storing a vast amount of data in a relatively small area, while also being able to withstand the harsh lunar environment.

How to make a library last for a billion years

Spivak wanted to avoid using traditional digital storage mediums like solid state drives, he told me, because they might be more susceptible to damage from cosmic radiation and because there’s no guarantee that whoever discovers the Arch in the future will be able to extract information from current devices. Instead, Spivak opted to print a facsimile of the entire English version of Wikipedia, which consists of about 6 million articles spanning around 25 million pages.

The Arch Mission Foundation partnered with a chip manufacturer—Spivak declined to name the company—to adapt a technique usually used to prevent counterfeiting money to printing really, really small images on metal. This technique uses lasers to print microscopic images on ultra-thin nickel discs. So far, this technique has been prototyped with images of the Foundation trilogy on discs the size of a dime. The disc that will carry the 25 million Wikipedia pages will be about the size of a DVD and consist of hundreds of layers stacked on top of one another.

According to Spivak, any future human (or extraterrestrial) that stumbles across the lunar Arch will be able to read Wikipedia with a common 1000x microscope—assuming they can decipher English.

A prototype of a nickel sheet printed with hundreds of pages. Each of these small squares represents one page and can be read with a 1000x microscope. Image: Arch Mission Foundation

The laser used to engrave the disk is able to print 300,000 dots per inch (DPI). To put this in perspective, most printers you’d find in your home or office max out at around 4800 DPI. According to Spivak, the patented printing technique will only take about a month to engrave the entirety of Wikipedia on the disk.

“We have the only capability in the world today to write this much data, this precisely, in such a small form factor,” Spivak told me on the phone.

In order to maximize space, Spivak and his colleagues are reformatting Wikipedia articles to cut bloat like white space and metadata. Moreover, the Arch Mission Foundation is developing an algorithm that will arrange the Wikipedia articles in such a way that they will be hyperlinked across the disk. In other words, if one article references another article, a reader will be able to locate that article on the disk using an algorithmic organizational scheme.

In addition to the English version of Wikipedia, the lunar Arch will also include a copy of the Rosetta project, a digital library of all human languages compiled by the Long Now Foundation. Spivak told me there’s also the possibility of including major Wikipedia entries in other languages, if storage space permits.

The lunar Arch is hitching a ride to the moon with Astrobotic, a company that aims to put the first commercial lander on the moon in 2020. Astrobotic was founded in 2008 and was initially developing its lunar lander as part of the Google Xprize race to the moon. Earlier this year, the Xprize was canceled after it became clear that no competing team would make it to the lunar surface by the March 2018 deadline. In spite of this, a spokesperson for Astrobotic told me that the company still plans on making it to the moon by 2020 and has already secured its spot on a Atlas V rocket.

A close up look at the individual pages printed on a nickel disk. Image: Arch Mission Foundation

In addition to the lunar Arch, Astrobotic will be carrying a number of commercial payloads including a “Moon Museum” designed at Carnegie Mellon University, a small rover, and the ashes of the dead.

It’s a reassuring thought that even if our species doesn’t make it—whether it’s due to nuclear folly or cosmic forces outside of our control—a diverse record of our existence will live forever on the only other celestial body our species has set foot on besides Earth. Even if the apocalypse never materializes, though, Spivak hopes the lunar Arch will be a source of inspiration for the Earthlings everywhere today.