We know incredible things about former civilizations thousands of years after they fell, thanks – in large part – to the tangible records they left behind them. But today, no one keeps physical records. No one writes letters. No one prints photos.

If, in 2500, a Museum of Earth History wants to curate an exhibit on life in 2015, they’d have nothing to put in the display.

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Many people assume digital files, including photos, letters and emails, will last forever in the cloud, on a computer or on a storage device. Not so, says Google Vice President Vint Cerf: “It’s clear that we stand to lose an awful lot of our history.”

“When you think about the quantity of documentation from our daily lives that is captured in digital form, like our interactions by email, people’s tweets, and all of the World Wide Web,” Google Vice President Vint Cerf recently said, “it’s clear that we stand to lose an awful lot of our history.” Cerf has even coined a term for it: “the lost century.”

This issue of digital archiving is not at all new, of course. Anyone who has ever saved a file to a floppy disk or filmed a home movie on VHS is keenly aware of, and probably annoyed by, the archival challenges of technological change. Already, only 20 years after their mainstream heyday, it’s really hard to find the software to read a floppy disk or an old-school VCR on which to watch a tape.

But the problem, it turns out, could go way beyond ye olde floppy disks. Sure, it becomes far more difficult to access digital information when the file formats, or the device they’re stored on, become obsolete. (Cerf himself is concerned with creating a “digital vellum” that would preserve outdated files, no matter their age.) That said, archivists have been able to pull data from decades-old computers and century-old wax cylinders. The really scary risk of loss may be when our data isn’t technically saved to any one discrete, physical thing, but is instead held in the “cloud” or by a private company.

After all, companies shut down every day – just ask Carter Maness, the music writer whose career took a hit when several of his past employers shuttered their websites and his writings were lost. Or talk to one of the millions of people who chronicled years of their lives on Journalspace. The once-popular blogging platform closed abruptly in 2009 when a disgruntled ex-employee wiped its database.

Or take the emails that Cerf referenced in his speech last week. Letter-writing is at an all-time low, per the U.S. Postal Service – most of our personal communication now takes place digitally – which means your inbox probably contains stuff that’s important to you: emails from old friends, photo attachments, family recipes. Whatever it is, it only lives on your email providers’ servers, and they can do with those what they wish. Who knows what will become of them, in 10 years or 20?

Here’s another example that’s pretty timely right now. A majority of parents now use Facebook to share photos of their children; in many cases, those photos likely only live online. (We know they’re not going in scrapbooks, anyway: For years, that industry’s been on the decline.) To the casual observer, Facebook seems like a safe haven for photos and other digital memories. It’s a large, stable company. It recently instituted a policy that would help you pass on those photos, should you pass away.

And until last week, it turns out, Facebook’s code also contained a bug that would have allowed a hacker to delete every photo off the site.

“We are nonchalantly throwing all of our data into what could become an information black hole,” Cerf warned in an interview with the Guardian. “We digitize things because we think we will preserve them, but what we don’t understand is … those digital versions may not be any better, and may even be worse, than the artifacts that we digitized.”

There are efforts to reverse this, of course – to preserve the Internet for posterity. In 2010, the Library of Congress famously signed a deal with Twitter to begin archiving every one of the network’s public tweets. The Internet Archive, meanwhile, has saved copies of more than 452 billion Internet pages, which will be preserved even if those sites shut down or change.

But while that may help humanity’s legacy, it doesn’t do much for the average Internet-user who just wants to nostalgia-scroll through old photos in a few years. What about my online journal? Or my baby pictures? Or my Pinterest collection of favorite recipes?

For those people, Cerf has some analog advice: Print out absolutely everything.