Well, you know right away that it's not a 'perfect' sphere, because it has
all of these lumps and bumps (mountains) and pits and carve-outs (valleys
and ocean trenches) all over it. So every point on the surface is NOT the
same distance from the center. The difference between the lowest point
on Earth and the highest point is more than 10 miles.
But even if you shaved down all the lumps and bumps and filled in all the
pits, then the Earth STILL wouldn't be a perfect sphere. First of all, the
circumference around the equator is about 83.49 miles longer than the
circumference around the poles. The Earth is like this rolly polly doughboy,
kind of short, with a bulge around the middle.
But it's even worse than that. If you cut the Earth in half through the
equator, then the two pieces you'd have aren't the same shape. The
top half is kind of thinner and pointier, and the bottom half is kind of
rounder and fatter; the whole thing put together is shaped kind of like
a pear !
Of course, it's so close to a sphere that when you look at it, you can't
tell the difference, and you say to yourself "Yep. It's a sphere." But the
question says "... perfect sphere", and 'perfect means only one thing.
There's no such thing as 'almost perfect', or 'kind of perfect', or 'nearly
perfect' or '99% perfect'. 'Perfect' means perfect, and the Earth definitely
is not that.
