Question: What is the highest we could build?

Edward Bovill answered on 12 Mar 2013:

The highest man-made structure on the planet at the moment is the Burj Khalifa tower in Dubai which is 829.8m tall. The engineering challenges involved in building it were staggering. At that height, the wind is so dangerous (it could blow the entire tower down) that they had to make it aerodynamically stable from all directions – which is why it is the amazingly organic shape that it is. To build even higher would require many more serious advances in technology and materials science.

However, there are some ideas out there that would make the Burj Khalifa tower look tiny in comparison. These ideas involve using spacecraft to knock an asteroid into a geostationary orbit around the Earth (this means that they stay over exactly the same place in the Earth’s surface all the time). Once the asteroid is in a stable orbit, a cable could be used to join the asteroid to the Earth’s surface and used as an lift cable to transport people and other things directly into orbit without having to use a rocket. This would make a structure that was 35,786km high, about 44 times higher than the Burj Khalifa tower in Dubai!

The idea is called a ‘space elevator’, and although currently there are no materials available that would be strong enough to make the cable, carbon nanotubes are a promising future material that could work.