There is a secret library in my world that contains all of the the world's known and unknown moments that had happened before whether if it is any scale of wars or an animal going extinct, the library contains it all, but for it to have this many books, how big should the library be? Would a city-size library be enough?

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    $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Commented Aug 4, 2023 at 3:48
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    $\begingroup$ How long is the world's history? What constitutes a "historical moment" - does a mountain getting created by volcanic activity and worn down to the size of a hill before the first creature existed in the primordial sludge count? What about a small hill? What about a pool of primordial sludge that doesn't quite evolve life? And so on... $\endgroup$ Commented Aug 4, 2023 at 5:30
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    $\begingroup$ That entirely depends on what is the intended meaning of the phrase historical moments. A rough timeline of the history of pre-imperial Rome fits in half a page. Mommsen's Römische Geschichte covers only pre-imperial Rome, has three large volume, and is little more than a high-level overview. The Corpus Inscriptionum Latinarum is currently at volume XVII and, of course, contains only those inscriptions which have been preserved, and not all of these. In a good library you will find half a shelf of books about the battle of Actium -- one battle, which was over in half a day. $\endgroup$
    – AlexP
    Commented Aug 4, 2023 at 6:39
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    $\begingroup$ What defines history? Let's leave aside primordial sludge - would a book entirely about the air currents that lead to a hurricane be "history"? History is fractal - every moment can be broken down into sub-moments, each of which has their own history leading up to them. $\endgroup$
    – jdunlop
    Commented Aug 4, 2023 at 8:08
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    $\begingroup$ The answer to this question depends solely on how you set the threshold for when a piece of information is significant enough to include in it. For exapmle, I guess you want to track leadership changes of countries. What about leadership changes of cities? Towns? Individual homesteads? I voted to close the question until significance criteria are added. $\endgroup$
    – Philipp
    Commented Aug 4, 2023 at 12:26

4 Answers 4


There are two variables that make this impossible to fully answer:

  • What is the threshold of importance for an event to be included?
  • How much detail should be given about each event?

We could look at is some orders of magnitude for the two different types of "history" you mention:

Human history

The number of "events" that happens probably scales roughly with the number of people considered - in a year of today's world of ~8 billion people, there are multiple large-scale wars comprising dozens of battles, multiple election campaigns and political scandals, hundreds of significant deaths, and so on; in a year of the hunter-gather society of the paleolithic, there might be only a handful of conflicts. We could perhaps guess at an average of one page per human lifetime. The total number of humans who've ever lived is estimated at around 100 billion over the last 50 thousand years or so.

The Wikipedia category "2019 events by month" (I figure the totals for the "pandemic years" might be unusual) and its sub-categories contain 17 thousand articles. That's roughly one for every 500 thousand people, per year - close to one for every 5000 people over their lifetime.

There are surely plenty of things that would count as "events" that don't have a Wikipedia article, so my initial guess of one event per thousand humans doesn't sound far off. That alone is 100 million events.

Biological history

The concept of "species" is an entirely man-made one, without one clear definition that can apply to all types of life, and all scales of context. The Wikipedia article on biodervisity quotes wildly varying figures for total number of species alive today, but gives an order of magnitude for eukaryotic species as about 10 million. Based on the idea that "more than 99 percent of all species that ever lived on Earth are estimated to be extinct", we can guess that maybe 1 billion species have gone extinct, over the last 2 to 3 billion years.

Encyclopedia size

Our estimates give us counts between 100 million and 1 billion "events". If we assume a short encyclopedia article for each, we can estimate the size of a printed copy.

As of this writing, Wikipedia has about 6 million articles, estimated to fill 3000 volumes, on 17 bookshelves. Our counts are between 20 and 200 times as large - 300 to 3000 bookshelves holding around 60 thousand to 600 thousand volumes.

Library size

For comparison, one of the largest libraries in the world is the US Library of Congress, which holds more than 30 million books, among other collections. That's 50 times the largest estimate we've come up with so far.

That collection is mostly housed in three large buildings in Washington, D.C. - nowhere near the scale of "a city-sized library".


A single copy of an encyclopedia with a brief of summary of every human and species-level "event" could fit into a single large building. However, that could easily expand by several orders of magnitude if it included more detail, or more categories of event.


And there are also many other things which Jesus did, the which, if they should be written every one, I suppose that even the world itself could not contain the books that should be written. Amen. John 21:25

The World is Big, Lots of Stuff Happens in It

If you were to record every "moment" of a single person's life, each nibble of food, each muscle twinge or twitch, it could fill a library. If you added commentary pointing out context, it would balloon even more.

There have been billions of people.

But a billion libraries intricately detailing the lives of every person wouldn't cover the tree falling in the forest when no one was around, the life of each ant in each anthill (quadrillions of ants), and a list of other things which list might alone fill a library.

The world could not contain a library which covered its entire history, unless it left most details out.


Hmmmm - so using Wikipedia as a Baseline - they have (at time of writing) 58,747,275 Articles and they estimate that if they were to be put into volumes like the Encyclopedia Britannica - that would be 2,657 Volumes or 14 Book shelves.

Easily achievable in an average city library. Hell, I've even been to hole-in-the-wall second hand book shops with more than 14 book shelves.


If I look at an article for say a certain mid-century Austrian Dictator, his article is 43 pages (single side) of A4, so let's say 22 double sided pages.

I have it, on quite good authority, that there is more information about said person than merely 22 double sided pages. There are countless books, all with original information, speculation, reasoned conjecture etc. etc.

There are a plethora of other historical figures for whom the same could easily be said.

If you limit yourself to the detail provided by Wikipedia (which for most things provides a good overview) and you use article linking (another great way that you save on space, avoiding the duplication of information) - then yes, it's easily possible to have a pretty good record of history and historical events.

But such a repository wouldn't be considered comprehensive. Many a YouTube historian has recorded rants about Wikipedia glossing over a lot of nuance and context and deep information for subjects that whilst may not disprove the information per se in Wikipedia, can certainly cast it in a different and less favorable light.

  • $\begingroup$ And must a library use physical books? What if the data are digitalized? Compressed size of Wikipedia (en.wikipedia.org/wiki/Wikipedia:Size_of_Wikipedia) is a mere 22.14Gb (exluding media). $\endgroup$
    – KC Wong
    Commented Aug 4, 2023 at 5:24
  • $\begingroup$ I agree that for many things, such as the biographies of obscure singers and the line-ups of soccer sides in presumably notable matches, Wikipedia does a good job. Unfortunately, history is not one of those things, and as for good outlines of history Wikipedia doesn't even know what they might be. (This is by policy. Wikipedia is not a real encyclopedia, but rather a mindless summary of secondary literature. It is not possible to write a good outline of history under this restriction.) $\endgroup$
    – AlexP
    Commented Aug 4, 2023 at 11:57
  • $\begingroup$ @KCWong In your world, you can. But here the querent was quite clear they wanted physical books in a physical library :). $\endgroup$ Commented Aug 4, 2023 at 14:57

The Akashic Records

There is no way of saying how many books this would take because there is no way of deciding on a single threshold of information. In theory, your library could be so vast and detailed that it would collapse into a black hole and consume the entire universe growing until there are no future events left to record... or it could be just a few book shelves, just depending.

Instead let's try looking at this from another angle. How can you have a library with an infinite amount of knowledge, not consume an infinite space and mass?

According to Theosophy, the Akashic Records are a non-physical recording of everything that ever has and ever will happen, anywhere in the history of the universe. This "record" exists in a transdimensional state of existence that can in theory be accessed from anywhere through careful meditation, but it takes great wisdom and training to discern information conjured up from the Akashic Records from one's own desires and imagination.

So, if your library itself is transdimensional, then the question of size only comes down to what you need to be able to access it. Your "library" could a monastery full of wisemen who devote thier lives to meditation, answering people's questions or writing down books from record. Or it could be a single magical book that acts as a focus, filling its pages with information from the record. Or it could be a place that you go when you meditate where the image of a library is just your brain's representation of the infinite knowledge at its disposal. Or, it could be a special computer system that taps into the record and delivers information like ChatGPT.


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