Let’s say every man, woman and child on Earth dies of whatever reason you fancy. How long before evidence of human habitation is gone? Will it ever?
Would a city abandoned for 1000 years look much different from one after 100? 10?
Will reinforced concrete eventually disappear? Glass? How about big chunks of radioactive material, nuclear waste, etc? Fancy mechanical parts and medical prosthetics made of exotic and durable metals, ceramics or polymers?
I am thinking that changes to the landscape would be the first to go, am I right? Dredged navigation channels; level surfaces for cities, airports, etc once the constructions are gone; landfills?
What would be first and last to go?
ETA: Please go as far as you need, geological timescale is welcome.
That’s so sad! HC and Discovery have some really good programs once in a while… and if you’re on Straight Dope, my guess is that you’re the curious, intellectual type. May I ask (out of curiosity) why HC doesn’t appeal to you?
When the book was first released, the author appeared on The Daily Show. It was quite interesting. IIRC, he said one of the most amazing things is how quickly cities would be overcome. But, at the other end of the scale, plastics and metal man-made objects would probably last for millennia.
They are, sadly, none too picky when it comes to the quality and accuracy of the programming they air. That said, they aren’t actually responsible for the content of said programming so some are certainly much better than others.
I can’t answer for Sapo, but i think the History Channel is, for the most part, a load of shit.
Even when it was focusing on actual history, it was nearly always WWII or the Civil War. And now that they’ve shifted away from that, things have actually gotten worse. Shows about psychics, the paranormal, UFOs, monsters, etc., etc. It’s a joke.
Of the few interesting shows they have, most now have nothing to do with History. Hell, one of its highest rating shows of all time is Ice Road Truckers. Quite interesting, but not exactly history.
Discovery is really hit or miss for me. Some shows I love, some I hate. Very little in the middle. Ditto for TLC (except for a much lower batting average for TLC, which is now turning into baby and fashion channel)
The History channel has a lot of slideshowy shows, way too much Hitler, those “we are shaking a camera filming boring stuff to make it seem dramatic”, way too much Hitler, poor production values and way too much Hitler.
I have liked many of their shows, btw, it is just that their batting average is below average for me. I am now liking the Science channel a lot more (isn’t it also a Discovery network channel?)
Tends of millions of years later evidence of dinosaurs are readily and easily found. Billions of years later we can find evidence of single cell organisms from back then. I’d imagine that within the lifetime of the solar system there’d probably be some evidence to skilled searchers that we’d been here. Fossils. Unnatural earth formations. Trash left on the moon. A layer of increased radioactivity in a geologic layer around the world from nuclear bombs testing and general industrial activity. Etc.
Major meteor impact. Giant tidal wave comes along, knocks over the Golden Gate Bridge (or significant pieces of it), covers it in mud. Dust cloud from impact triggers massive ice age drawing down the water level of the Bay drying the mud of its corrosive water. Movement of glaciers fills bay area with rock and soil. 600 million years later aliens dig and find bridge amazingly intact. They build a tourist visitor center with interactive displays prominently featuring the 2003 Mercedes SL500 and occupants found with the bridge section.
Anyway, I was just offering my sense on the answer to the first two questions in your post. I have no idea of specific numbers for the others.
Geosynchronous satellites are going to still be up there right up until we take them down for some reason, or the Sun goes giant and swallows the planet.
LEO orbits do, but that’s because they aren’t entirely out of the atmosphere; there is still some slight drag and they need a supply of fuel to periodically add energy to make up for the losses.
After the next ice age, there will be no trace of New York City. In the last one, that region was scraped right down to the bedrock by glaciers a thousand feet deep.
At the rate that a carved granite grave headstone deteriorates, I’d say it would take at least hundreds of thousands of years, and perhaps much longer.
And the pyramids at Giza - are they wearing away fast enough to prevent some remnants remaining evident a million years from now?
But these glaciers are pushing all that stuff somewhere, right? Maybe the Empire State Building won’t be recognizable as such, but I bet a quarter in someone’s pocket might.
Strictly speaking, all orbits decay, but geosynchronous satellites are up high enough that it would take a fantastically long time, longer than the lifetime of the Sun.
Come to think of it, the Voyagers, Pioneers 10 and 11, and a few other outer-system probes will outlast the Sun, even. Lots of luck finding them, though.