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What Is A Time Capsule?

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Time capsules can be buried, sealed in a vault, or even shot into space. They can be regular old boxes, enormous vaults, or a simple letter. Time capsules can take so many different forms that it's about time we ask, what is a time capsule, exactly?

I've been writing about time capsules for nearly a decade now, and the most common comment hurled in my general direction is, "That's not a time capsule!" Sometimes people get upset when a time capsule is interred for only a short period. Other times people have issues with unconventional capsule forms, such as a shoebox in a closet or a message in a bottle thrown out to sea. So what exactly is a time capsule?


William E. Jarvis literally wrote the book on time capsules with 2003's Time Capsules: A Cultural History. He breaks down the different kinds of time capsules, which I've adapted below so that us regular humans can understand it. (It's a great book, but Jarvis is a fan of describing things in philosophical Latin terms.)

The TLDR version: A time capsule can take whatever form you like and last as long as you like. They can be as simple as a newspaper accidentally left undisturbed in an attic for 100 years. Or they can be a vault sealed underneath a courthouse lawn with instructions to be unearthed in just 10 years.


Above all, time capsules are fun. So chill out and just make one. They're a helpful reminder that time marches on, with or without us.

Chicago mayor Martin Kennelly seals a time capsule in 1948 scheduled to be opened in 2048 via AP

Intentional, Scheduled

Of all the types of time capsules, this one is probably the most familiar to those of us here in the early 21st century. It's essentially any box or tomb that's sealed with instructions for people of the future that it's not to be disturbed until a specific date. These intentional scheduled capsules are often buried with a plaque nearby indicating when they're supposed to be opened.


They're most commonly buried with instructions to be opened in 50 or 100 years. But they can be as short as five or ten years, or longer than 6,000 years. The Crypt of Civilization, sealed in Georgia in 1940, isn't supposed to be opened until the year 8113. The first modern intentionally interred, scheduled time capsule is thought to be the "Century Safe" at the 1876 Philadelphia Centennial Exposition. It was opened on schedule in 1976.

Examples of intentional, scheduled capsules:

A subset of intentional, scheduled capsules is what I've deemed the "leapfrog capsule." These capsules are opened at a specific time and then re-interred, with people of the future adding their own contributions to the time capsule. In 1989 some 10-year-old kids in Washington sealed a time capsule vault with a pledge that they would return 25 years later to add more things. They did just that in 2014 and were tasked with recruiting new kids to carry on the tradition in 2039, adding things with each new generation every 25 years. This leapfrog capsule is supposed to continue until the year 2389 — the state of Washington's 500th birthday.


Voyager gold record time capsule via NASA

Intentional, Unscheduled

The intentional, unscheduled capsule includes things like cornerstone capsules, or the time capsule records inside the Voyager and Voyager II spacecraft currently teetering on the edge of our solar system. These capsules were created to be seen by future generations (0r, in the case of the Voyager capsules, Green Men from the Forbidden Planet) but they don't include instructions for when they should be opened.


Capsules included in the cornerstones of buildings are usually unscheduled because they're generally not opened (or sometimes even discovered) until a building is torn down.

Examples of intentional, unscheduled capsules:

  • Message in a bottle found at sea or on the shore
  • Coins buried in cans where the time capsuler's intent was unknown
  • Cornerstone capsules like the Paul Revere capsule of 1795
  • Bottles or boxes buried on private property (like the one I found a few years ago when helping a friend build a patio in his yard)

The intentional, unscheduled time capsule predates the 1876 Philadelphia Centennial capsule by hundreds of years. People have been putting things in cornerstones for countless generations. But the intentional, unscheduled style of capsule is slightly more controversial than a scheduled one simply because scheduled capsules became the norm for so many American children in school during the 20th century.


Accidental "time capsule" apartment from Paris via Daily Beast

Unintentional, Unscheduled

The unintentional, unschedule time capsule includes things like those apartments that are sealed up and forgotten about for whatever reason until they're finally discovered many years later. Even tombs and shipwrecks undisturbed over a period of time can be considered unintentional, unscheduled time capsules.


No one sealed these particular time capsules with the intent of them being opened at some far point in the future, but that's precisely what happens.

Examples of unintentional, unscheduled capsules:

These kinds of time capsules are often the most difficult to classify as time capsules, because they're not boxes buried in the ground. But they're still time capsules! And often include fascinating pieces of recent (or even ancient) history.


Essentially, there are no rules. The time capsule police won't show up at your house and say "that's not a time capsule!" just because you found a photo of your family from five years ago and would like to call it one. But hopefully these classifications help you decide what kind of time capsule you'd like to make, or determine what kind you've found, should you ever be so lucky.

Some people get upset when a time capsule is unearthed before they consider it "old," but that's of course incredibly subjective. Good manners dictate, however, that you don't dig up time capsules prematurely if they've been explicitly schedule.


Again, there really are no rules. But if you're going to make your own and bury it in the ground, let me give you just two tips:

  1. Make sure to build your capsule water and air tight (putting things in the ground is literally the worst way to preserve something)
  2. Put something interesting inside so that people of the future aren't bored to tears

Happy capsuling, everybody!