You know those angel Apocalypse stories where angels come down and kill all the humans? Well, I'm writing what would happen if the angels had won, and what happens after. So it goes like this: The angels appear and demolish cities. Their goal wasn't to destroy man-made things, but that happened to most buildings. Some people wrote down what happened on paper and stored them in safes or underground.

So the Earth is humanless for about 25 million years, long enough to form super Pangaea, and then humans are now back on Earth, but are all much stronger, faster, and can use magic, but know nothing of what happened. Would these new humans be able to find information left behind from the old humans? What tech would they find, what history would they know about? Would all the animals and plants die from the sudden change to the environment? How evolved would life be? Would it be possible to use books made of interactive holograms while still using wooden ships that belong in the age of sail? Or have modern plumbing but only matchlock guns?

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    $\begingroup$ At the moment your question is a bit broad. Your question is basically, what can happen to earth in 25 million years without humans. The answer is: a lot. YOu also ask if you can have two different levels of tech use together, which doesn't have much to do with the rest of your question. You'll have to focus your question on a certain aspect. But be careful that you don't ask a duplicate question. $\endgroup$ – overactor Nov 20 '14 at 7:07
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    $\begingroup$ There's How might modern humans leave a message for 50,000 years? as an example of a question that's close to what you're asking. $\endgroup$ – overactor Nov 20 '14 at 7:09
  • $\begingroup$ The question is simmilar but no duplicate. 50k and 25M is a big difference on how earth will change and thus how things will be gone, or not. $\endgroup$ – jawo Nov 20 '14 at 7:47
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    $\begingroup$ @Sempie, it's not a duplicate, that was meant as a related question, the problem is the wide range of questions in the second paragraph, though both answers so far have largely ignored it. $\endgroup$ – overactor Nov 20 '14 at 9:43
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    $\begingroup$ When I use numbers so big is because I don't want to "simulate" the state of the world until the target date. 25M years is a lot, a lot may happen, including things coming from space that affect the surface of the planet or its life. You have a lot of creative freedom, nobody can say anything about your world because nobody knows how Earth might be in 25M years. About preservation of information, I don't think It can last so long, except there are a fantastical solution for that in your story. $\endgroup$ – Hatoru Hansou Nov 20 '14 at 12:00

About zero.

Perhaps anomalous DNA sequences (that humans genetically engineered), assuming the organisms' species line didn't die out in the interim. And that the DNA didn't get redacted by natural selection.

You're going to only have a few chunks of crustal plate that're still around. Almost everything else will have cycled, at least once. Weathered and washed down to the bottom of the sea (ie: as rust & dust particles; not as buried treasure).

And, perhaps, fossils. But, the rate of fossilization is pretty low, and doesn't capture a lot of data.

If humans were really smart, they may have dumped something in amber. And if that amber didn't get eaten by the plate tectonics, something hungry, etc - perhaps, maybe. But you're looking at digital info (size restrictions, you're not putting a book in sap and hoping for it to last) - and no known way of reading it (machines are dust on the wind), or microfiche.

Perhaps the Long Now Rosetta Project pieces might be around.

But, you're running about 2500x as long as their clock project might be operable. They're only hoping the clock will work for 10K years. Which is a long time, considering weathering and everything else.

Some things in space might be around. But solar-wind and micrometeorite impacts will have done a number on them - unless they're buried somewhere on the moon (perhaps Mars, it's not very active). But getting that type of information up there after your event is going to be very tricky. And why would your magical people know that they need to look there, or even be able to find it without a pointer?

25MY is a [diagnostic] long time to try and preserve anything.

Also, it's not a duplicate question - since many of the answers in the 50K year question, are relying on humans being around in the interim. For language continuity, if nothing else (they suggested creating cultures, religions, atomic priesthoods, etc.)

An aside, one of the answers suggest embedding stuff in diamond. Diamond isn't a very good preservative. It cleaves fairly easily, and it burns in the presence of oxygen and heat.

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The answer depends heavily on how you define information, but generally "no useful data available."

One key point: much of what will happen over 25MY is stochastic -- random. If you need to say "this body of 100kB survived perfectly," then there is virtually 0 chance it does, no matter how it was stored. If you relax that to "some random X% of the data survived," you can start to keep things for long durations.... it just wont be easy.

25MY is a geologic timeframe. You're talking about the difference between the earliest dinosaurs and now. That's a beast of a timeframe and a lot can happen!

The biggest focus I would have is on the spatial frequency of information. Right now, humans are compressing their data onto things like hard drives, which store information in microscopic regions on a metal platter. Storage in small areas like that is rated on the order of 10-50 years. Books, despite inferior building materials, are still readable a thousand years later, mostly because they store the data in a larger format. Clay tablets last even longer, as do stone inscriptions. The larger the medium, the more it survives.

If we are talking about a timeframe similar to that of the dinosaurs till now, expect significant sediment to gather, and do so slowly. Everything humans will have done in our entire civilized era will be compressed into a layer a few millimeters deep. The surviving things will mostly be the few things that were not broken or oxidized before getting compressed into oblivion, and then torn at with forces strong enough to sculpt the Fjords of Norway (which, is believed to have occurred no more than 0.1MY ago).

But what if civilization is actively trying to preserve data?

What if the civilization undergoing Armageddon is actively trying to preserve its data for 25MYa? It could not preserve much.. the forces of geology are unrelenting. However, if it is a small bit of data, say the name of the Archangel which destroyed the world, there's a chance. The trick would be getting the signal to noise ratio high enough to survive the random effects of geology (we're assuming geology is not an intelligent adversary actively seeking and destroying data). A small amount of data could be replicated over the entire earth, in hopes that things can be stitched together. This would effectively be a Raid 6 storage array on steroids.

However, we would have to find the data, and know where to look. Something replicated that many times would look like a curious noise pattern. We would need to clue the next civilization in.

*(Note: I'm calling the the next civilization. I think it is fair to assume that in 25MY, the progeny of humanity will be so unbelievably different, both in shape and in culture, that we might as well treat them as an alien race)

One solution which seems legitimate is fractal encoding, where the same message is encoded at many different sizes. This would be an effective process for saving information like that because it is reasonably likely that the next civilization would be looking for life, and that kind of pattern is really hard to arrive at without life on that planet. They'd be looking for A message, and would hopefully find the message we are looking for.

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...' - Isaac Asimov

The final challenge is linguistics. We lose languages in hundreds of years with ease. Making sure the message is understandable when we return 25MY later is a challenge on par with the Voyager Golden Record. How you overcome that difficulty would be on you.

Your final question about mixed technology really deserves its own question, because it is MUCH less related to information storage. However, generally speaking the answer is no: you do not see technological gaps like that. Engineers and scientists and inventors are just to bloody creative. They will dismantle what it took to learn to construct a rifle or a holoplayer, and rapidly apply that technology to everything. It will not take long to "fill in the gaps." Just look at how rapidly western technology ripples through a primitive culture over the course of 50 years, much less 1000 or 25000000 years.

"Inspiration unlocks the future; technology will catch up" - Caproni in The Wind Rises by Miyazaki.

The one exception that I see would be Arthur C Clarke's definition of magic. If the new tech is so unbelievably advanced, it would be indistinguishable from magic. This would protect it from the prying eyes of the curious. However, it would also mean the only advanced devices would be those which survived from 25MYa, because they wouldn't be able to create new ones. This puts us right back at square one: keeping something intact for 25MY is hard!

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25M years is plenty of time. Enough to get all the stuff far under the surface, lets say todays oil-level or deeper.

This makes it unlikely that anything would be found on the surface at all. Due they do not know anything about the history of former menkind, they will not search for their footsteps.

The magnetic poles are changing over time. Last time a significant change of over 50° was 800M years ago. This drift was so massive, that the icecaps have melten completely then. It's unlikely, but not impossible that this happens again and one cannot be sure that ice conserves over multiple millions of years.

But where would the have a chance to find our tracks?

  • Fossils

    Look how fossils form to get the idea. Almost everything could form to fossils, so this is a good chance.

  • Outer Space

    In earths orbit, things are pretty well conserved. Sunerruptions, meteroids and so on, will destroy most of it, but due their well conservation it's unlikely that nothing is left.

What would they where able to find?

  • On Earth

    As I said, almost everything. But mostly substances which do not rot and are able to resist (relative) high pressure like plastic. Anything organic will be gone and would, when at all, be visible through their fossil image. Mineral structures, like metalwork or buildings will be gone, if not cutting off corrosion which means that, even under the surface, there must be an waterproof soil above them. If not, a skyscraper of glass and steel would only left a potential ironmine behind.

  • In Orbit

    If they've gone that far, they're surely pretty impressive in technology and have found things under the survace already. So they probably wound be that horrorfied of this high-technologie in their earths orbit (Like we had been. Just imagine what had been happened if first men in space had found trash of other civilisations in our orbit,... aliens????)

    So this source of informations about the past is reliable. When they're steping off the atmosphere, here they will find foodsteps for sure! But what they will find is not that much (seen from the exactly point of today). It's a very confined image of our culture due we only stepped in space for exploration and science, nothing more. This will show them some of our high-end technologie but nearby nothing about the culture which has formed this great stuff.

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  • $\begingroup$ My data wasnt right, fixed it. But the magnetic poles due indeed change their position. Last time this had happened with more than 50° of change is 800MY ago. en.wikipedia.org/wiki/True_polar_wander $\endgroup$ – jawo Nov 20 '14 at 8:37
  • $\begingroup$ Nobody disputes the change of position of the magnetic poles. It is just that such wander won't affect the longitude or latitude of the points of the surface. $\endgroup$ – SJuan76 Nov 20 '14 at 8:41
  • $\begingroup$ Clima is relatet to the Sun. If earths poles, and thus the rotational axie, changes, then regions have massive climatic change. It's good to talk about his due it might help the TO to figure his world out in which always is alot of fiction and the idea of future is alwas speculation, but one cannot say that the ice is endless in time. It's just wrong. $\endgroup$ – jawo Nov 20 '14 at 8:48
  • $\begingroup$ @Sempie I don't know where you got your information from, but I'd urge you to actually look it up again. Magnetic pole reversals are much more common then you claim (happening about every 500,000 years), and there's no real evidence to suggest that they have any significant effect on living organisms. They certainly don't cause polar caps to melt (although something else in that time might've). $\endgroup$ – Cubic Nov 20 '14 at 13:02
  • $\begingroup$ @Cubic "I don't know where you got your information from" - dude, I linked it... $\endgroup$ – jawo Nov 20 '14 at 13:33

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