Expert: Tom Whiting - 2/13/2009

Question
can you tell me at least 5 facts that can justify that the earth is spherical and not flat.

Answer
Hi Mary,
Yes, I believe that I can come up with five (or more) reasons for that one.
1. The ancient Greeks saw that during an eclipse of the moon, our shadow was a curved line against the moon. (And not a straight line). Over a period of time and several total lunar eclipses, even they were able to deduce that the Earth had to be spherical and not flat.

2.  It was noted back in the middle ages that when a ship departed
the harbor, it eventually disappeared from view over the distant
horizon...from bottom to top, and not just get smaller and smaller (but still visible)...thus the ship was following a shallow curve, and not a straight line or flat plane.

3. If you've ever been in an airplane above 50,000 feet (Oops, flight
level 500) or higher, say to clear the tops of some thunderstorms,
then you can physically "see" the very shallow curvature of the
Earth. Pilots of the SR-71 had no trouble seeing it at above 80,000 feet, and of course the astronauts in orbit....a no brainer there.

4. We orbit artificial satellites; in low orbits one trip around takes about 95 minutes.  If the Earth were flat, I guess a satellite
would just continue in a straight line, never to return or go into
"orbit" around the Earth; thus the Earth has to be spherical, not flat.
5. By inference, IF the Earth were flat, how could the moon maintain
its elliptical orbit around the Earth without colliding with a flat
extended Earth?  Therefore, we deduce a spherical Earth.
6. All the other large bodies, sun, planets, moons, etc. we see through our telescopes...are spherical....so why would the Planet
Earth be....so much different than those?
7. If the Earth were flat, and given over 10,000 years of human
civilization and migration, don't you think that by now, someone
somewhere would have already discovered..."an edge" and perhaps fall
off, or report nearly...falling off?
8. I believe a guy by the name of Magellan circumnavigated the globe
on a ship, way back when.  That trick would be impossible if the
Earth were flat.

9. And by today's standards, we've been to the moon 6 times
(actually 8 if you don't count landings, like Apollo's 10 and 13)...
where the astronauts actually saw a spherical Earth from a distance
rotating and moving thru space...so that one kind of clinches it, Eh?
10. In mathematics, once you obtain the mass of the Earth, there are
physical laws and formulae in place which state that since we are over a certain minimum mass and density, the Earth HAS to draw itself into a spherical shape for the minimum surface area. (Even our moon beats the minimum, so it is also spherical, even though it's only about 1/4 our diameter)...but I slept thru that class.

Hope this helps,
Clear skies,
Tom Whiting
Erie, PA