Assuming that the Earth is a sphere and its orbit around the Sun is a circle, how do you find the volume of the torus that is just sufficient to accommodate the Earth?
The volume of the torus is
#2pi^2(orbit radius)(Earth radius)^2 cubic units
#=2pi^2(1495987871)(6378)^2 cubic km
To accommodate Luna also in this this torus tunnel, its cross
sectional radius has to be increased by the apogee distance +radius of the Moon of
Luna from the Earth.
The volume of this wider tunnel
#= =2pi^2(1495987871)(6378+405400+1737)^2 cubic km
As [the Earth](https://socratic.org/astronomy/our-solar-system/the-
earth)'s and Moon's radii are 4-sd approximations, these related
approximations are restricted to 4-sd