# Old Planets



## ephemeraldeep (Nov 10, 2013)

Hey people, I've been trying to figure out what my world would be like if it was significantly older than earth is right now, maybe 1/2 million to a million years older or more. The world is not earth, just similar enough that having sources on what an old earth would be like would be very helpful. I have tried looking online, but it's mostly religious stuff about how the earth is actually 6,000 years old, so not quite what I was hoping for.
Any help is welcome!!


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## teacup (Nov 10, 2013)

Not sure how the actual planet would be, but I assume that everything would be more evolved than it is now. I've heard it was terrible, but maybe "After Earth" could give you some good ideas?


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## Lycan999 (Nov 10, 2013)

There is almost no way to tell. It would mostly depend on the choices the inhabitants of the world make, it could end up anywhere from a inhabitable waste land to a thriving metropolis of advanced beings. Half a million years is a strange number, the planet would probably not have changed much naturally but the inhabitants could have done a great deal. You have given yourself enough time to shape the world however you see fit, just come up with a believable history.


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## ThinkerX (Nov 10, 2013)

No significant difference.

Variation depends more on other things, like where the world is at in its stars 'habitable zone', composition of the crust, amount of water on the surface, ect.

Now, if you have a very young world - less than a billion years old - that does affect things.

Earth, for example is around 5 billion years old (I've seen different ages given from 4 to 5 billion years), yet has had a breathable atmosphere (for current lifeforms) for less than a billion years.  And until around 600 million years ago, life on land of any sort pretty much didn't exist, and for a long, long while after that (hundred million years or more) it was basically just plants.  

Millions of years, barring something like getting hit with a 'dinosaur killer' type asteroid, or a million year long ice age, doesn't really count.


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## Captain Loye (Nov 10, 2013)

The comments above are pretty much on the mark - changes to biological systems generally happen over millions to tens of millions of years. Geological changes like mountain formation and continental drift are more like hundreds of millions of years.

Today our world is cooler and drier than most times in the past few hundred million years. An older Earth might keep cooling and drying, or it might get hot and wet again (eg, climate change).

There are some pretty cool eras in Earth's history that you could check out on Wikipedia etc for some inspiration on what a slightly different Earth might look like (these are past, but the same conditions could easily happen in the future too):

First, there's the classic dinosaur eras - the Jurassic, Triassic and Cretaceous. Each had its own systems, but generally the world was warmer and wetter, and covered in huge forests of giant ferns and pine trees and everyone's favourite giant reptiles.

Going back further, there's the Carboniferous. This was before mammals, reptiles and amphibians existed, and oxygen levels were much higher. The whole world was basically huge, crazy ferns and giant-sized insects (like 2ft dragonflies - see Meganeura).

Finally, going right back to the Cambrian is cool for some of the craziest organisms to every live. This was purely aquatic, there was no thing on land at that point in our history, but definitely a good place to look for animal-inspiration.

If you're looking specifically for an old Earth, try looking at areas in Western Australia (The Pilbara is one of the oldest landscapes on earth - no significant geological processes except for weathering in 3.5 billion years). That is what most of Earth would look like today without processes that renew soil like volcanoes and tectonic activity.


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## psychotick (Nov 12, 2013)

Hi,

Strange question. First a million years is nothing geologically speaking. A million years from now, assuming we don't stuff it up, geologically speaking the Earth will be more or less as it is. In another billion it'll probably have changed.

Biology is fickle. There's no way to know what life will be like in a million years on Earth. Evolution will have made some changes, but likely only small ones. But bear in mind that entire ecologies can die out in incredibly short time periods. This is Stephen Jay Gould's stuff so google him. But periodically there have been mass extinctions, and I'm not just talking about the dinosurs. Every so often something goes wrong and vast numbers of species are wiped out and then what survives has to go through a period of relatively quick change as it has to adapt to the new environment / ecological niches. (And of course there's no guarantee that we as a race won't sterilise the Earth in a century through pollution, global warming, and nukes, and it'll be a hundred million years before a new ecology arises to replace us.)

But neither of these things is going to mean much when if you're talking about an alien world you have no idea of where it began. You have no baseline to compare young to old.

If you want to show age, your best bet is to ignore both of these things and instead look at civilisations / anthropology. At present we have evidence of cities going back six or seven thousand years - all the way to Babylon and ancient Mesopotamia (and of course China). But in a million years, assuming that those civilisations built in permanent materials, we could have ancient ruins dating back - well say half a million years. Cities from endless different civilisations - because they inevitably rise and fall. And because people will inevitably build in the same places, new cities will be built on the remains of old ones,so as you dig out the foundations for a new house you could be unearthing fossils from hundreds of thousands of years before.

Cheers, Greg.


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