What is keeping us from anchoring a cable to Earth’s surface and tethering a platform in space?
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All the top comments are bringing tensile strength, but another major issue is resistance to heat and friction.
While most of a space elevator would be outside the worst of it, the portion between 0 and ~80km is going to be experiencing drag from the atmosphere. While it’s possible to make it long enough that the counterweight balances out the drag which would make it *collapse*, that’s tens of kilometers of material which is being consistently blasted by air going speeds of upwards of 450km. That air carries ice and dust.
You would make the assumption that since it’s high altitude it’s cold, which it is, but relative temperature matters a lot in this case because so far humans don’t have any materials which don’t become brittle at low temperature. On top of that, all the strong stuff we have has very low ductility (the ability to bend and shape).
So the moment, even the stuff we have that is theoretically strong enough *also* becomes brittle at low temperatures *and* can’t withstand the friction.
There’s actually a fantastic point in *Project Hail Mary* where this problem is addressed. It’s by Andy Weir, the guy who wrote *The Martian* (which the movie is based on). I definitely recommend it.
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