According to Relativity, considering Lorentz Contraction...
For cosmic ray protons, for example, moving at 99.9999999999991% of speed of light, the Earth only appears 17 meters thick, essentially flat
I make the point in this blog:
http://smithsk.blogspot.com/2015/08/physics-part-2-flat-earth-it-depends.html
So it’s all relative. ;)
But if the cosmic ray were to perform the experiment from all angles, it would conclude that the results are isotropic and that the earth is indeed spherical but with a diameter of 17 meters.