Wired magazine reports that on this day in 240 B.C.E. the Greek geographer Eratosthenes calculated the circumference of the earth using measurements using a well and a column. He was pretty close in the actual circumference but his computations weren't accurate.
2248 Years Ago Today: Eratosthenes Measures Earth's Circumference
By Matt Rosenberg, About.com GuideJune 19, 2008
Explore Geography
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Except for the trivial case of a few rather tiny rocky planets and moons, when we talk about the size of an atronomical body we mean the size of a ball of gases. (Some could have solid cores.)
If we were to measure earth that way, that is, to the “top” of our atmosphere the circumfrence would be 25,089 miles assuming the stratosphere extends 30 miles. So a jet flying around the earth might indeed go very close to 25,000 miles. Curious.