An Interesting Film

I saw a movie called Agora.  At first I thought the movie contained a serious scientific flaw.  I thought that the main character, Hypatia, was indicating that the earth was closer to the sun in the summer than in the winter.  This is only the case in the southern hemisphere.  The earth is closest to the sun sometime in the first week of January, which is winter in the northern hemisphere and summer in the southern hemisphere.  The time of perihelion is given here.

However, on closer examination she only says that the sun has a different apparent size.  The link above provides a list of inaccuracies in the movie.  One of them was that the earth's orbit is so nearly circular that she wouldn't be able to see the difference with instruments that were available to her at the time.  I found this hard to believe since Kepler, who discovered that the planets have elliptical orbits around the sun was going by observations made by Tycho Brahe.  I thought these were very good naked eye observations, but it turns out that they involved sophisticated instruments even thought the telescope hadn't been invented yet.  These instruments would not be available to Hypatia.

The movie doesn't have Hypatia carefully observe the orbit in order to determine that it is elliptical.  As I stated above, her concern is that it appears to change in size.  It is probably not the case that she was able to determine that the earth has an elliptical orbit about the sun, but the difference in apparent diameter is about 3.3%, which is the same as the difference in the sun's distance.  It seems plausible that someone would in her age would be able to detect a difference in apparent size of one part in thirty.  However, I don't think there is any record of her having done so.

Another supposed error was that the film stated that she was an atheist, whereas she was supposedly a pagan in real life.  The historical account of Hypatia given in Wikipedia states that there are no contemporary statements about her religious observance.  It was stated that she was pagan two centuries after her lifetime.  If this is the case, it is not clear what her position on religion was.  However, the film seems to accurately portray her as teaching both Christians and pagans.