The loose idea of this structure is in my world a secret society believes the Earth is going to be heavily damaged in the near future by war and that humanity will be pushed to the brink of extinction and reverted back to the Stone Age, losing most of humanities knowledge. Therefore this secret society in theory plans to have this temple be dormant during the fall of Humanity and remain largely intact for hundreds if not thousands of years, keeping the encoded inscriptions on the walls reciting the Societies history intact.

Along with keeping the temple and its information intact, the society would also plan to incorporate some sort of robots, or mechanisms, that can be reactivated by someone who has sufficient knowledge to decipher the inscriptions sorta similar to how in Avatar - The Last Airbender you see the Avatar statues light up and “activate”.

The main problems of this question are:

  1. How would such a Temple be built to last?
  2. How would the inscriptions be encoded places on the walls that would mean they could only be decrypted by someone of advanced knowledge (Eg modern knowledge)?
  3. What capabilites could be build into the temple hat could “reactivate” after the Fall of Humanity?
  • $\begingroup$ Welcome to WorldBuilding, Vampman500! If you have a moment please take the tour and visit the help center to learn more about the site. You may also find Worldbuilding Meta and The Sandbox (both of which require 5 rep to post on) useful. Have fun! $\endgroup$ Commented May 31, 2018 at 21:05
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    $\begingroup$ Funny you mention Avatar, since in their obligatory Indiana Jones episode the answer to "how are the long-dead civilization's traps still working" is (spoilers I guess) "maybe they aren't dead?" $\endgroup$
    – Cadence
    Commented May 31, 2018 at 21:07
  • $\begingroup$ Welcome to WorldBuilding! You might be interested in some of our existing questions, such as Ancient Light Trigger Mechanism and How might modern humans leave a message for 50,000 years? Have fun on the site! $\endgroup$
    – Secespitus
    Commented May 31, 2018 at 21:10
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    $\begingroup$ There are many thousands of architects, engineers, and investors who would love to know the answer to affordable, long-term, maintenance free construction. $\endgroup$
    – user535733
    Commented May 31, 2018 at 21:18
  • $\begingroup$ For decryption barrier, have your messages encrypted with a relatively weak cypher. That cypher would not be broken with pen and paper, but a powerful computer would do it in short time. $\endgroup$
    – Alexander
    Commented May 31, 2018 at 21:20

5 Answers 5

  1. The key thing here is to build in stone. Steel rusts, wood rots, but while stone can chip and crumble, massive stone structures tend to last. (Think of the Pyramids, for instance.) You'd want to build in the right place, too. Low humidity is good, earthquakes are bad. Build into the earth, if possible; even just a few meters below the surface, you can benefit from much more consistent temperatures.

  2. Assuming that the inscriptions exist, and that the language is readable, there are a number of ways you could keep the information out of the hands of passers-by. You could encrypt it, for one. Either your secret society records the key elsewhere, or they write down the key in the temple and accept that anyone with sophisticated enough machinery can decrypt it. (Or they could not include the key - a mathematical cipher like Enigma is just barely breakable with mechanical means, but a modern computer could brute-force it easily enough.) Another option is to encode information in terms of physical constants - you could look at how the Voyager plaque was encoded, for instance. This would make the data largely meaningless for anyone without accurate measurements of those constants, but fairly easy to decode for a technological society.

  3. Unfortunately, this requirement is largely incompatible with the first. Blocks of stone and carvings on them can last thousands of years, but more intricate mechanisms don't stand a chance. You could store arbitrarily-complex components on their own, in some kind of vacuum-sealed container; that would keep it from physically degrading. Most forms of electronic data have a short shelf-life, but very simple programs could be encoded in a physical pattern of electronic elements that would be safe. Adding chemical treatments to avoid rust or mold, and storing in a dry place at a constant temperature would also help. However, somebody would then have to undo all this storage work - the instructions for that could be encoded in the message in part 2, of course. Also, batteries are unstable over long periods of time, so your secret society would need a way around that.

It won't be as simple as "go into temple, push button", but with some thought and a lot of groundwork, you could preserve a fair amount of knowledge for a long time.

  • $\begingroup$ I think the OP may mean that the encryption should be easily breakable by anyone with modern knowledge. If that's the case, the method of using the key to decrypt the information can be written in plain english (or whichever language is common in the area) and the instructions can include hints to the key, like a puzzle in the newspaper. The answers to the clues should rely on common (modern) knowledge, like the molecular makeup of water (H20) or the names of major countries based on their flags (USA, Russia, China, Japan, etc) $\endgroup$
    – Josh
    Commented May 31, 2018 at 21:58
  • $\begingroup$ @Josh I was interpreting "modern knowledge" to be more along the lines of "modern scientific knowledge", hence the idea of using a code that would be difficult if not impossible to break by hand, but trivial with more computational power. $\endgroup$
    – Cadence
    Commented May 31, 2018 at 22:09
  • $\begingroup$ For part 3, while robots and the like might not be good, with batteries and electronics not lasting long even when stored properly, a purely mechanical computer can exist. Take a look at the Mark 1 Fire Control Computer from WWII - Purely mechanical, and instructions can be left as to its assembly, operation and function. Such a machine could be designed that could then manufacture significantly more complex things if given the appropriate starting materials. There's limits, of course, but the knowledge on the walls is more valuable anyway. $\endgroup$
    – Andon
    Commented Jun 1, 2018 at 0:39
  • $\begingroup$ Just copy the bitcoin mining algorithm. Write it on the wall. You can only really do it if you have a digital computer. $\endgroup$ Commented Jun 4, 2018 at 1:13
  1. keeping the temple and its information intact

    Primitives who gain access to the temple might destroy it. Even well intentioned folks might screw up the temple when they went in. They might add things of their own, or erase important stuff. Exactly the right kind of person might find the temple, understand the walls, write it down, get all excited and leave with the knowledge except right outside is a bear which eats him and then bears move in and scratch up the walls.

    You need your temple off of the earth's surface. The moon would be good, or in orbit. Periodically the temple launches a re-entry hardened capsule, which lands in similar place(s) each time. Within are the humanity instructions. If they are not understood, ok. If they get lost, wait 10 years for another one. Bears and zealots and tsunamis and the changes of Earth will not destroy your temple. It might be hard to visit but that is ok. You do not want visitors.

  2. they could only be decrypted by someone of advanced knowledge (Eg modern knowledge)?

    I don't get this. You want to wait until someone has regained the modern knowledge of humanity before you deliver them the knowledge of humanity? That is like requiring someone make you beef bourguignon before you give them the recipe for scrambled eggs. Your instructions are not for people who have already reclaimed modern knowledge. You want your instructions decipherable by the butt-ignorant. Those are the people who need them!

  3. Reactivate -

    naw. Stay active. Or countdown 50 years and then start sending the capsules. If humanity doesn't fall, it will be intrigued and amused by the capsules.

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    $\begingroup$ I like the idea of periodic capsule launches - 10 years for a thousand years is only 100 capsules, and they could be launched by solar powered magnetic catapult, thus saving on volume for fuel. Have the reentry on nighttime territory for maximum three-kings-lure effect. Capsule could also sport a few commandments for faster society-building. $\endgroup$
    – bukwyrm
    Commented Sep 11, 2018 at 14:50
  • $\begingroup$ @bukwyrm - 3 Kings Lure! Nice! That would be a fine book title. $\endgroup$
    – Willk
    Commented Sep 11, 2018 at 16:54

The temple is a space station in high orbit

In space, there are very few processes to degrade materials or otherwise destroy the temple. There is plenty of solar power to keep the monitoring systems active.

The temple is awakened by radio signals

When someone figures out how to build a working radio transmitter, the temple will hear their signal and reactivate.

When reawakened, the temple de-orbits a self-piloting module and lands it near the signal

Depending on how fantastic this temple is, it could either send a shuttle that can bring people back up to the temple station to read the messages, or it could send a simple lander capsule that contains the messages.


In a fantasy setting the temple could be designed to be self repairing so rather than designing mechanisms to endure eons, it would be capable of self diagnostics, maintenance and replicating worn or damaged components.

Realistically though the issue of how build a structure that will last and communicate with other humans hundreds of thousands of years into the future has been pondered over by scientists designing storage facilities for nuclear waste and was the subject of a Finnish documentary called Into Enternity

And here are a couple of articles looking at the issues involved with communicating a complex idea like the threat of toxic radiation to a far off future link 1 link 2

  1. You can take any material you want as long as:

    • you ensure the entire temple is time dilated
    • it's nuclear-powered (fusion or fission: up to you) which will also solve a lot of other technical problems down the road in your story...

    With fission, showing itself 1 day per year, it could travel up to 8760 years into the future with a 24-month life cycle of the fuel rods before showing itself permanently and:

    • 17520 years if it comes out of time dilation once every two years
    • 87600 years once every 10 years,
    • ...

    With fusion and time dilation: a bucket of heavy water could keep it going for 100s of thousands of years...

    With current technology using a Liquid Metal Nuclear Reactor, the temple can be big compared to the reactor. (USS Nimitz size)

  2. The lock itself would have the be based on universal constants: You can take any, but taking Pi as an example, you can time the technology level quite precisely:

    Historical precision of PI calculation

    And the lock can only be tried 3 times! After 3 failed login attempts, it jumps ahead in time to the next year / decade / ...

  3. Anything that is big enough to fit in the temple: Computers, planes, food & drink dispensers (for the hungry/thirsty explorer), art forms (statues, paintings, music, ...), the Bible, the Al-Quran, ... whatever you need in the story.


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