In response to Write once perpetual storage, is such a thing possible? Separatrix pointed me at How could an ancient race warn the future in a universally understandable way? and How might modern humans leave a message for 50,000 years?. While neither question addressed my concerns they have made me ask something else that will be useful much later, and possibly elsewhere too:

Given modern materials what would be the best method for creating a long term record/warning of events, on the planet's surface, if we only had three days, or at most, a week to do it?

I'm not asking what the message should contain or how it should be encoded, I want to know what medium it should be written on that will last as long as possible and can be fabricated in minimum time.

The message will cover approximately 1200 A4 pages or 75m² of surface area, and will include both written and pictorial information. This is the absolute size of the representation that must be produced. Answers need not worry (nor consider) scaling it, or compressing it etc.

Out of scope for the purposes of this question: anything about how such a message might, or might not, be translated in future, the message can be assumed to be translated as long as it is still legible. The message will be outside in an environment that gets only occasional light winter rainfall and is otherwise geological extremely stable and sheltered from erosion.

The society leaving the warning has no expectation of survival and wishes to leave a warning that lasts as long as possible. They only have one shot at it and very limited time, which means they must use their currently existing technology. If we were leaving such a message on the surface of the planet, starting tomorrow, what material would we use?

Important note:

The message must be readable without auxiliary technological assistance, so they could, for example, use laser etching to write the message, but not an encoding that requires a laser reader.

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    $\begingroup$ Is a magnifying glass considered to be "auxiliary technological assistance"? $\endgroup$
    – Neil
    Commented Jul 31, 2018 at 13:16
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    $\begingroup$ Also, what is the time period? is it 50,000 years like in the linked question? $\endgroup$
    – Kepotx
    Commented Jul 31, 2018 at 13:17
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    $\begingroup$ @Kepotx Like the question says "as long as possible", they have no expectation of being around to find out. $\endgroup$
    – Ash
    Commented Jul 31, 2018 at 13:21
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    $\begingroup$ @Neil Yes, the physical size of the message is already set you can't shrink it. $\endgroup$
    – Ash
    Commented Jul 31, 2018 at 13:24
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    $\begingroup$ @ArtificialSoul Use the answer section for what it's there for. $\endgroup$
    – Ash
    Commented Jul 31, 2018 at 13:46

7 Answers 7


You set three primary goals:

  • Achieveable in a few days
  • Sustaining the elements since it is supposed to be outside
  • Lasting as long as possible

The key is a protective, transparent layer over your message

Whatever material you use steel plates, ceramic tiles or etching in plain old stone, the fine details of the etching are significantly easier to use than the rest of the material. The details are what is more vulnerable, more exposed and also more crucial.

Transparent durable plastic is suited for this as it is not biodegradable (yay, long-lasting pollution!) and - as it states - transparent. So you can cover your etched material entirely in it and have it still readable while not being as exposed to the elements.
Even if the surface is partially damaged you can get a different angle and still see what's beneath. And even if it is mostly damaged you can still see there is something under there and remove the top layer and you can read it again.

Getting etchings on steel plates and putting a thick layer of plastic on it is probably achievable within a single day.

Placement is important

While you can place the writings in the desert, not only do you risk them being buried within years, but also damaging the surface significantly and thus reducing readability.

If you place them in an area relatively void of natural disasters and extreme climates (like most parts of europe) on the darker side of a mountain range (less UV light damaging the protective surface), it should last a while.

You also need to make sure it is anchored well. So a slight earthquake does not make it all tumble downhill.

Additional highlighters might be nice if you want to draw attention to it. Like big pillars or completely evened surrounding area, so it is easy to see from the air.

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    $\begingroup$ I hadn't thought about sign posting the location, that's a good thought. $\endgroup$
    – Ash
    Commented Jul 31, 2018 at 14:38
  • $\begingroup$ plastic will eventually get scuffed up from dust/sand being blown, etc. $\endgroup$
    – ivanivan
    Commented Aug 1, 2018 at 1:34
  • $\begingroup$ @ivanivan that is correct, i did mention that. The idea is placing it somewhere, where this happens less, and also the main goal is preserving the message and making it visible that there is a message. Even if there is a huge block of plastic mounted to a mountain range, somebody is gonna notice it. It will be obvious there is something and the message is still there. Even if not as readable as it was in the beginning, i can be made as readable again. $\endgroup$ Commented Aug 1, 2018 at 6:59
  • $\begingroup$ Plastics, in spite of popular myth, tend to degrade rapidly as far as useful life is concerned. The plastics in the space suits from the lunar landing are deteriorating at a rapid peace in spite of being tended in a museum with all the experience and tech to preserve fragile artifacts $\endgroup$
    – pojo-guy
    Commented Oct 2, 2018 at 22:20

In such a short space of time your best medium is probably glazed and/or shaped ceramic tiles. While better can be achieved with more time ceramics can last an awful long time and are already produced on mass, if mass panic can be avoided then ceramic producing facilities could easily be re-purposed to create as many copies of the message as possible increasing the probability that one copy of the message survives. These copies should then be sent by plane to a wide variety of places preferably deserts, tundra etc... and buried in pyramid like structures which are then buried in earth. One copy should be put in geostationary orbit where it will last pretty much indefinitely (provided it doesn't collide with anything) though will require space travel to access.

People will eventually dig at these oddly square mountains a little and (hopefully) find lots of pretty tiles. Even if these people have no interest in what the tiles say they will still dig them up for use in construction (assuming they are from a pre-industrial society that is) and likely the pretty patterned side is the one that they will show meaning your message will at least be seen.

We have pottery from almost 30 thousand BC so this has a lot of longevity to it. Your biggest worry is making a universally understandable message.

In truth though the best option is every option since we're all about to die in three days it really doesn't matter if we bankrupt the economy printing millions of sheets of laminated paper, creating massive earthworks in the shape of giant letters, sending people to the moon with buckets of red paint and hiring every artist in the world to paint it in a cave somewhere. If this is the plan people have decided on just go all out and hope that quantity brings the message to the next civilisation.

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    $\begingroup$ +1 for every option is the bet option. Cost is very irrelevant at the point if you are committed to delivering the message. $\endgroup$ Commented Aug 1, 2018 at 5:57

How do you leave a message for future generations when all you have is 50 acres and a JCB?

I think you can guess where this one is going, but Earthworks are one of the more remarkable and long lasting features of ancient civilisations. Whether barrows, dykes or ancient fortresses, banks and ditches are incredibly long lasting in their effect. Even when "destroyed" they leave their mark on the land for a long time, detectable thousands of years later with ground penetrating radar and showing up in the grass during droughts.

While density of information isn't the strong point of this particular medium, shear size allows for considerable noticeability to future generations.

  • $\begingroup$ That is going to be a much larger message plate than I had envisioned, it would probably work but I have my doubts about noticing that something that large, especially under vegetation, is what it is but +1 for an original approach. Could we get it done in a week? $\endgroup$
    – Ash
    Commented Jul 31, 2018 at 13:50
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    $\begingroup$ @Ash, consider the Nazca Lines as an example but with the aid of GPS plotting and industrial equipment. I'm betting it could easily be done in a week. $\endgroup$
    – Separatrix
    Commented Jul 31, 2018 at 13:56
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    $\begingroup$ Add a concrete pour in the trench for extra longevity. $\endgroup$
    – Jammin4CO
    Commented Jul 31, 2018 at 15:58

Repeated Message in Multiple Languages on a Durable Material in a Geologically Protected Location

Etched or carved metal and stone tend to survive throughout the ages. Technology for polishing and inscribing stone and metals such as aluminum at the industrial scale exist. As such, draft the message and have as many copies made as possible.

Aside from hard stone engraving, there are corrosion resistant alloys already produced in abundance that could be employed. Some examples are:

Space Age Example

Use a durable material

NASA offered their take on this in the 1970's Voyager's Golden Record. Essentially, inscribe your message on an durable material, and include rudimentary pictogrpahic instructions for replay.

Classic Age Example

Write in multiple languages

For less celestial timelines, the important trick seems to be to inscribe the message in multiple languages to improve the chances that it is interpretable by a future human civilization. The Rosetta Stone is one of the most valuable archaeological finds because of this.

Prehistoric Example

Store in geologically protected location

The paintings of Chauvet Cave are still interpretable by modern humans, but the message is probably less precise than you're looking for. Take away advice would be to put your message in a geologically protected place.


You can have people 3D print the message on their personal and business printers. Most plastics never biodegrade, except in very specific conditions, so they should last for 50,000 year. As other answers suggest, having multiple copies will make survival of the message more likely.


Granite, slate, ceramics, concrete, and other hard natural materials can be milled or laser engraved/cut with the message as well. Many maker/hacker-spaces have CNC mills and/or laser cutters capable of doing this, as well as private businesses. It would only take a trip to the local home improvement store to get a stack of pre-made 10-12" square tiles to get this project crowd sourced, same as the 3D printing.

You can also mill and/or laser cut sheet plastics. Acrylic is cheap, flexible, stronger than glass, and readily available. Polycarbonate isn't as laser friendly, but will still etch and is tougher than acrylic. Both can be sourced as 4 ft x 8 ft sheets.

Crowd sourcing is probably the best way to get a large message like this together in a short time, and it gets around the so called "one shot" you think you have time to make. Giving small sections to a variety of people with specific instructions on how to make the end product will give you the quickest results. To hedge your bet, you can give one group instructions to do a set in laser etched polycarb, another group CNC mill engraves it into granite headstones, another group is told to 3D print it, etc. Once the individual pieces are finished, they are co-located and assembled into the finished product, with each groups efforts being distributed. What I mean by that is maybe the headstone groups is in Los Angeles, the 3D printer group in New York, and the polycarb group in Denver.

You can even have this duplicated in each continent, to hedge your bets even further. So, for example, the 3D printing is also done in Melbourne, Paris, Moscow, London, Capetown, and Rio de Janeiro.

Each continent or location can have their own translation, so it becomes a Rosetta Stone, in case one or more language is more easily decipherable by it's finders than another language. Some of these translations can include pure math, binary, pictorial, as well as current spoken languages.

Also, remember to number the pages, somehow, so your message isn't garbled when the cargo container is ripped apart and spread across 3 square miles of ocean floor. Or whatever.

With potential dozens of these messages around, someone is likely to eventually find it. Someone will do some spelunking in caves that used to be Buddhist temples, find perfectly straight holes in the ground with radioactive rust piles at the bottom (missile silos), and other locations were the message copies are stashed. A reasonably smart (or lucky) being will decide that all the sheets of plastic (and piles of oddly shaped rock) that have etchings on them mean something, will want to get them into one place, and may even start to figure out that there's a real message in all that (presumably) purposeful surface scratching and/or raised ridges.

Edit: Units are there for a rough comparison of size. I doubt that a country that uses SI units is going to have products that measure exactly 4 ft x 8 ft panels, as that comes to oddly specific (and fractional) 1.2192 m x 2.4384 m. I would hope they round to something "normal"/"useful"/easy-to-measure like 1.5 m x 2.5 m. Or maybe they use 2 m x 2 m panels. I haven't lived in these countries, so I don't know what size building materials actually come in. So, I don't see how converting from UCS to SI units really adds anything meaningful to this answer.

Edit 2: Polycarb is more scratch resistant than acrylic, and can have a scratch resistant coating added, like they do for glasses lenses.


Also, I don't see how people would use table tennis balls for this message, since nitrocellulose is the "spontaneously combust"able plastic Mark is talking about in his comment.


Acrylic is more temperature sensitive than polycarb, and acrylic can be used without warping up to some pretty extreme temps for the surface of the Earth. "It can be used continuously in a temperature range of 170-190°F. It begins to soften between 210-220°F and starts to melt between 300-315°F..."


Just because it's called "organic" doesn't mean it's found in nature. Organic solvents are man-made and have a low boiling point, so even if they were naturally occurring, they would boil away too quickly to do any real damage in even room temperatures.


UV light can damage some plastics, but it can also be hardened against the effects.

"Many of us benefit from UV radiation-cured protective polymeric coatings, such as polyurethane-acrylates, on exterior automobile components."


Some plastics aren't as susceptible to that damage as, say, polypropylene.

"Unmodified types of plastics that are regarded as having unacceptable resistance to UV are POM (Acetal), PC, ABS and PA6/6. Other plastics such as PET, PP, HDPE, PA12, PA11, PA6, PES, PPO, PBT and PPO are regarded as fair. Note that a PC/ABS alloy is also graded as fair. Good resistance to ultraviolet rays can be achieved from polymers extruded by Zeus such as PTFE, PVDF, FEP, and PEEKTM. The only plastics found with excellent resistance are the imides, Polyimide (PI) as used in the Hubble Space Telescope and Polyetherimide (PEI)."


  • $\begingroup$ Plastics may not biodegrade, but they break down in other ways. For example, polycarbonate has low scratch resistance, while acrylic is vulnerable to a wide range of organic solvents. Other plastics are vulnerable to ultraviolet light, or warp in even moderate heat, or spontaneously combust. $\endgroup$
    – Mark
    Commented Jul 31, 2018 at 21:32
  • $\begingroup$ Interesting idea, could you either put those measurements in S.I. Units that match the question or at a minimum add a conversion to them please. $\endgroup$
    – Ash
    Commented Aug 1, 2018 at 11:36
  • $\begingroup$ Side note, the most common 3D printing plastic, PLA, will decompose quite quickly. A few months in the right conditions, up to a few hundred years in unfavourable conditions. ABS should fare better but is a little less common and harder to work with. $\endgroup$
    – Bob
    Commented Aug 1, 2018 at 13:04
  • $\begingroup$ @Bob, actually, most 3D printers are capable of printing with a wide range of filament. Right now, PLA happens to be a very common choice. Just 2-3 years ago, ABS was common. You don't have to change print heads to go between PLA to ABS, so I don't see a problem with the message originator specifying print material along with dimensions. $\endgroup$ Commented Aug 1, 2018 at 13:07

This is already sort of being done

There's an effort to preserve knowledge for the ages at the moment, inspired by Sumerian tablets: http://www.bbc.com/future/story/20161018-the-worlds-knowledge-is-being-buried-in-a-salt-mine


The Memory of Mankind team hopes to create an indelible record of our way of life by imprinting official documents, details about our culture, scientific papers, biographies, popular novels, news stories and even images onto square ceramic plates measuring eight inches (20cm) across.

These are hardened, Alkalai, acid and extreme temperature resistant ceramics, engraved with up to 5M characters, or 50K characters with pictures. they are then stored deep in a salt mine in Austria (the salt helps prevent moisture).

They also produce small simple map tokens identifying the location in Europe, if these are lost then some larger, cruder installation above ground could be enough of a pointer for your future seekers of knowledge to be aware there's something there, then delve in to find the detail.

  • $\begingroup$ Welcome to Worldbuilding! Interesting find! - Do you know how long it takes to engrave these ceramics? $\endgroup$ Commented Aug 1, 2018 at 7:32
  • $\begingroup$ Sadly I can't find any specific data on that; I imagine their exact production specifications are something of a secret. However, laser engraving is a well established process these days (you can buy small engravers for home use) so I don't see it taking an enormous amount of time. The challenge seems to be storing the information in recognisable formats - we can't assume that the languages in common usage today will be still in use 1000s of years in the futre $\endgroup$
    – ErosRising
    Commented Aug 1, 2018 at 8:38
  • $\begingroup$ Nice, I'm kind of set on having the thing outside but the environment I've picked won't be much more erosive than that salt mine. $\endgroup$
    – Ash
    Commented Aug 1, 2018 at 11:02

Engrave your message in large-ish (big enough to be seen/found) gold plates, perhaps 1/4" thick and engraved/carved to a depth of 1/8" - nice and deep, keep the image around from wear, etc. over the years. Don't use 24k of course, 14k would do. Multiple copies in multiple locations. Mark locations with big huge solid construction of something, just to attract attention to it. Shiny. Durable. No corrosion, etc. to worry about.

Edit to follow up on several comments

1/4" is 6.35cm 1/8" is half that...

If you feel that gold - even a 50%-ish alloy - is too soft and bendy, a harder metal could be used, and a thick gold plate covering it to protect it from the ravages of time and chemistry. Additionally, having multiple copies in multiple locations would help ensure that one or more of the copies would be viable when found. To protect against looting, simply make the core large enough and heavy enough that anyone with the technology to move it, etc. would be able to notice the warning and perhaps investigate that before recycling it.

  • $\begingroup$ A problem with this approach might be that the gold gets looted and reworked into jewelry? Akin to the grave robbers that looted the pyramids. $\endgroup$ Commented Aug 1, 2018 at 10:53
  • $\begingroup$ Interesting idea, could you either put those measurements in S.I. Units that match the question or at a minimum add a conversion to them please. $\endgroup$
    – Ash
    Commented Aug 1, 2018 at 11:37
  • $\begingroup$ I am not sure what you are referring to by 24k and 14k. Also gold is not that strong. Something dropping onto it could rather easily deform it and the message is lost or corrupted. $\endgroup$ Commented Aug 1, 2018 at 11:51
  • $\begingroup$ @ArtificialSoul That'll be Karat, a unit used only to describe the purity of Gold. $\endgroup$
    – Ash
    Commented Aug 1, 2018 at 12:49
  • $\begingroup$ @Ash Ah, okay. I didn't know there is a notation like that for it. I just know the common one around here. (585, etc.) $\endgroup$ Commented Aug 1, 2018 at 13:29

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