# Why would a space elevator / structure need to be in Geosynchronous orbit?

I've read a bunch on space elevators and from what everyone is saying, it would be required that the elevator is in geosynchronous orbit. From my understanding, that is so that it would stay fixed in one position over the earth.

Also, from my understanding a space elevator would be some sort of cable that runs up into space and so people would essentially ride that cable up. Now that would also explain why it would need to be in geosynchronous orbit, since the cable would then otherwise wrap itself around the earth.

That got me thinking though, what if you were to build a super-structure from the ground up. Something similar to the image below. If you were able to create a structure strong enough to withstand the all of the elemental forces in the upper atmosphere:

• Would it be possible to have the structure sticking out into space, but not in geosynchronous orbit?
• What would be the challenges in creating a structure like this?
• Could something like this change the earths rotational period?

• The thing though is that the compression strength of materials is generally a lot smaller than their tensile strength. Add that to how even small strength differences grow exponentially, thus the ground-up design has a major drawback. Aug 19 '16 at 17:17
• Arthur C. Clarke, if I remember correctly, had such structures in his book titled 3001. There were four towers, every 90 degrees around the equator, made of diamond. They reached into space, where a ring connected the tops of all of them. All that diamond came from the core of Jupiter (or something like that)... Aug 19 '16 at 17:33
• You'll need to build your towers from unobtainium. Aug 19 '16 at 21:44
• You sound like a person that needs to look up skyhooks. Have fun on that rabbit hole! Here’s a starter: m.youtube.com/watch?v=dqwpQarrDwk Jun 4 '21 at 13:46

I've read a bunch on space elevators and from what everyone is saying, it would be required that the elevator is in geosynchronous orbit.

The center of gravity of a space elevator would need to be at geosynchronous altitude, which means that a space elevator would need to be extend well beyond geosynchronous altitude.

• Would it be possible to have the structure sticking out into space, but not in geosynchronous orbit?

• What would be the challenges in creating a structure like this?

The key challenge is strength of materials. The tallest structure built to date is "only" 829.8 meters tall (the Burj Khalifa), and the very top of that structure is exceedingly narrow compared to the base. A building under construction will reach about a kilometer into the sky. It might be possible to build a structure ten times this tall, but that means the top is still well within the troposphere. Building a structure that is a few hundred kilometers high is not possible given our current understanding of strengths of materials, not even a mountain made of diamond.

Furthermore, even if it was possible to build a structure that was over a hundred kilometers high, it wouldn't be particularly useful for space exploration. There are two key obstacles regarding space exploration. The lesser of the two is climbing out of the bulk of the Earth's atmosphere. The far more significant obstacle is achieving sufficient horizontal velocity so as to be in orbit, and a one hundred kilometer tall structure will not help solve that problem.

A space elevator is a bit beyond the reach of current science and technology, but it's within an order of magnitude. A structure that reaches only partly into the sky is several orders of magnitude beyond the reach of current science and technology.