For example if you wanted to store data in a time capsule for like 100 or 200 and you where ganrateed the people on the other side had a reader capable of reading whatever media, and whatever format you chose.
Edit: 100 - 200 years is probably 2 to 5 pandemics, some of which may be considerably worse than the last one; and plenty of time for fires, floods, storms, earthquakes, and/or war (civil or other). Granite has a track record. Some stainless steels might be OK too (not for much longer than 200 years, though).
the library of congress uses contemporary storage media (hard drives), and migrates everything to newer storage media as the previous media becomes obsolete and replacement hardware for that media stops being manufactured.
they have learned that stockpiling old reading hardware and software isn't sufficient to be able to read that media in the future.
they move everything to new media manually and archivists and volunteers work continuously to bring data on hardware more than one generation old into the current generation as everything progresses.
source: I read it in a detailed article about the LoC a couple of years ago and have forgotten where. :(
Fired clay tablets are much more resistant, but lower density (because clay), unless you use a dedicated press maybe (most of the ancient Near East clay tablets were actually fired fortuitously e.g. by a building burning down, that was only rarely intended and most tablets were used as erase-boards). But obviously non-tablet pottery can go through millennia in rather good conditions.
Carved wood is also a good idea, but it still needs good conditions and maintenance. Still, in the right storage it can last for centuries (see the Tripitaka Koreana for instance).
Leather, parchment, and vellum too, but I think then your main concern will be the degradation of the pigments.
If your focus is on longevity above all else, then you can’t beat stone. Though that can still be destroyed. I guess above stone would be highly non-reactive metals, however you’d need a metal which is not very precious as well (e.g. not gold, or silver, or platinum). I’m not very versed into metals and metallurgy, but I’d look towards titanium (it’s extremely reactive but not at normal temperatures), or bronze.
At one point there were disks made out of glass (versus the conventional polycarbonate), in theory that gives them infinite lifetime short of being physically destroyed. Though it does assume a compatible drive device.
Stone can degrade as well. Basalt can absorb CO2 [1], marble is vulnerable to acids [2], and generally acid rain is a huge problem for historic buildings [3], as is bird poop [4].
Probably the only material impervious to damage is diamonds.
[1] https://www.geo.uni-hamburg.de/geologie/ueber-das-institut/n...
[2] http://intlstoneworks.com/blog/2018/03/13/substances-that-ac...
[3] https://www.lwl.org/pressemitteilungen/nr_mitteilung.php?url...
[4] https://www.mannheim.de/de/nachrichten/taubenschmutz-und-den...
Diamonds burn, and have the same problem as precious metals: getting stolen and repurposed.
> Stone can degrade as well.
Yes, but that doesn’t mean you can beat it.
And obviously you’d pick your stone based it’s characteristics and the environment, you wouldn’t record your message to the next generation on pumice.
The problem is not wood paper as such, it's production processes that leave some acidic substances in the paper, which causes it to become yellow and brittle on a timescale of a few decades.
Acid-free paper will easily last hundreds of years, and is nowadays easily available.
We have family photos from the 1800s. Every bit of computer data I have from the 90 is gone.. except what I printed out.
There is always a trade-off between mass, durability, and data density. I know you excluded those considerations, but for only 200 years in a time capsule you likely don't want to use large stone blocks or stainless steel.
The tape has several advantages. Mylar is very light and kept in the dark at a constant, reasonable temperature is going to last two centuries no problem. You can read the tape by hand, if you need. An 8-bit tape is an inch wide and can be rolled into a canister for your time capsule.
Of course, for small amounts of data print English words on acid-free paper. For large amounts, tape is going to blow out the mass budget you didn't know you had because of it's low data density. But there might be a space in there somewhere for a tech I loved as a kid.
I'd actually expect such a CD to last tens of thousands of years.
For your requirement of 100 to 200 years, a pressed (not burned) CD might well be sufficient if the storage conditions are optimal (cool, dry, no oxygen).
[1] https://www.engadget.com/2006-10-22-near-perfect-glass-cd-hi...
[0] https://longnow.org/ideas/02008/08/20/very-long-term-backup/
"With appropriate, difficult to maintain, storage conditions, this film has a life expectancy of ~500 years."