Adam Brown

It doesn't even touch the Earth.

It's not like a compression structure that's like a skyscraper that's pushed up from below.

It's a tension structure that's held up from above.

But as you go up, because you need more and more tension, you also need to make the rope thicker and thicker and thicker.

And if you try and, on Earth or around Earth, build a space elevator out of steel, say, it just doesn't work.

Steel is not strong enough.

You need to keep doubling the thickness until by the time you get to...

geostationary orbit the thickness of the steel rope is more than the size of the earth like the whole thing just doesn't just doesn't work at all uh but carbon nanotubes are this material that we just we've discovered that are much stronger than steel so in fact around earth carbon nanotubes will just about work if we can make them long enough and pure enough and

then they will be strong enough that we will be able to build a space elevator around Earth in maybe sometime in the next century that you only need a couple of doublings of the thickness of the carbon nanotubes along its entire length.

So carbon nanotubes work great around Earth, but they are totally inadequate.

for black holes.

For black holes, the critical material science property you need for this rope is the tensile strength to mass per unit length ratio.

It needs to be strong, high tensile strength, but low weight, like light, low mass per unit length.

And that's the critical ratio.

And carbon nanotubes is 10 to the minus 12 or something on that scale.

And that is simply not strong enough at all.

In fact,

what I showed in my paper, is that you need a

tensile strength to weight ratio that is as strong as is consistent with the laws of nature.

So in fact, the laws of nature bound this quantity.