I did enjoy reading this short story (nominated for a Nebula award in 1985)
in which the famous Greek mathematician Eratosthenes determines the Earth's
circumference and meets a shipwrecked alien, but I am seriously troubled
by it's
historical innacuracies. It is true that Eratosthenes
(also known for his work on prime numbers) came up with a very good
estimate of the circumference of the Earth. His method involved using a
deep well to determine when the sun was directly overhead at one point and
the measurement of a shadow at another point. (If you want to reproduce
his experiment, you can follow the steps at this friendly
website aimed at middle-schoolers.) However, Harness has a very
strange idea of what the world was like and especially what was
known at the time.
For instance, Harness has Eratosthenes recognizing that the "other planets" go
around the Sun just as the Earth does. Since he is told by the alien
that the Earth goes around the sun, I am willing to believe that
Eratosthenes could handle this idea. However, he would never have thought
this was consequently true of the "other planets". The ancient Greeks did
not think of Earth as one of the planets. In fact, the word "planet"
itself derives from the fact that they thought of planets as wandering
stars and had no way to think of them being in any way like the thing we
live on. Similarly, there is no reason to expect that he would be able to
conclude from this that the sun is just a star which we are close to...this
is not really a logical consequence of a heliocentric solar system.
Moreover, the mathematics he consults does not sound believable to me.
This story takes place long before the decimal numbering system that we are
familiar with, and before trigonometry as we know it. I could be wrong
about this (please correct me if you know!) but I seriously doubt that you
could have looked up a table of values of the tangent function in 160 BC.
I'm sure there are other historical innacuracies. (He has a "rabbi" there
among the non-mathematical figures that Eratosthenes encounters. My
understanding is that there was no rabbinic Judaism at this point in
history. Again, correct me if I'm wrong.)
If none of the anachronisms or innaccuracies bother you, what about the
idea that on the day after he has determined the Earth's circumference,
Eratosthenes just happens to meet an alien who needs this exact piece of
information to be able to return home?
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