Living on a building's surface in "Farewell Horizontal"

Question

I read "Farewell Horizontal" a long time ago. It described people living on the surface of a really big building, in particular, sometimes standing perpendicular to the wall. My physics is a bit weak, but wouldn't this put some tremendous pressures on the ankles? Have rock climbers figure out how to do this?

Also, in the same book, they mentioned motorcycles zipping around on the surfaces. If I remember correctly, motorcycles zipped around at 50 mph for significant amounts of time, which made me wonder exactly how big that building could be-- a one or two hour drive at those speeds straight up should take out right out of the atmosphere and into thin air and eventually vacuum. How big can a building get before it moves into fantasy land?

Answer 1

If the building was substantially solid (non-hollow), say at least 80-90% solid mass, there is really no upper limit on the size of the building if it were constructed of materials such as stone or steel. The building could be as large as any 'rocky' (non-gas giant) type planet.

However, if the building were constructed along the lines of today's modern skyscrapers with more than 90% of the volume of the building being empty space, then there is a very definite upper limit on the size. Given today's building practices, material strengths, water and air handling technology; the upper size limit for a single 'building' would be about the diameter of the Pentagon in the United States, and about twice the height of the new Burj Khalifa in Dubai. Assuming near-infinite funds. Much beyond that size, and the building would start to collapse in on itself.

If you throw in science fiction advances in materials and construction methods, you can go bigger. How much bigger depends on how advanced your materials science is assumed to be.

When you get right down to the question of 'Can a building be massive enough to have its own gravitation field?' The answer, in our universe, is: Only if it is mostly solid matter, and contains no significant internal structure as you would find in today's definition of a building.