MovieChat Forums > Agora (2009) Discussion > Ellipse and seasons

Ellipse and seasons

posted 10 years ago by elzosmid
5 replies | jump to latest

While everybody complains about how historical (in)correct this movie (!) is.
Nobody seems to care that the whole idea of earth having a changing distance to the sun is bogus.

Earth's orbit is an ellips, but almost a circle.

The sun does not look smaller in winter and bigger in summer. It's not a question of cumulating knowledge, this has never been observed.

And any change in distance does not account for the seasons as is suggested in the movie (seasons are caused by the tilt of the earth axis relative to it's orbit).

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[–] Clusium 10 years ago

Well, contrary to what the movie implied, Hypatia was not an atheist. She was a pagan.

If you love Mary and Jesus Christ and are 100% proud of it, copy this and make your signature!

[–] Blueghost 10 years ago

But given her example, would it not stand to reason that because of what you observe in relation to standing near and far away from a fire would also apply to the Earth?

And, for the record, it actually is the distance that determines seasons, though it's through geographical orientation, and not so much the change in radial distance from the sun.

[–] bodhiBard 9 years ago

You have to put yourself in the mindset of her time and the available knowledge. You saw how outrageous of a concept it was that first the Earth was not the center of everything. The circle was a perfect shape. The heavens had to be perfect. She questioned what she believed. It would have been an even more radical idea to imagine the Earth tilting. The ellipse was already radical enough and it fit. One breakthrough idea doesn't mean it is the absolute truth, it is just a stepping stone to a bigger truth. The Earth does travel in an ellipse around the sun. It also tilts. With the observations and information she had, she could rationalize the ellipse. She lacked the tools to observe the tilt. Its understandable.

The whole point was that her brilliance was lost. She could have single handedly discovered a singularity but her death and the destruction of her work meant it was lost forever. Blind faith destroyed knowledge and progress.

[–] thelongblondes 9 years ago

Firstly, this part was completely invented by the writers.
Secondly, it's pretty clear that the writers really thought the seasons were the results of the ellipse.
Thirdly, even if she truly had the right idea, her reasonning was competely wrong and she would not have been able to prove anything. She had nothing absolutely nothing. Just a concept with no scientific evidence.

[–] Sonlee 8 years ago

She lacked the tools to observe the tilt.

That's not correct. The tilt can be observed by the changing position of the sun in the sky and gradual variations in the amount of daylight as seasons progress. In fact the earth's tilt was approximated hundreds of years before Hypatia's time. As for the seasons, it's not that hard to imagine that periods with less than half a day of daylight would be colder than periods with more than half a day of daylight. The relationship between the earth's tilt and the sun are actually easier to grasp and (just as importantly) observe than the notion of an elliptical orbit.

The biggest obstacle preventing a late 4th/early 5th century astronomer from recognizing the earth's or any other planet's orbit as elliptical (not circular) wasn't the complexity of the idea, it was the precision of the measurements available. Kepler had more precise instruments available to him than Hypatia, hence he was able to see that a circle, whether it was centered on the sun or centered on the earth with the planets following various "eccentricities", did not fit the available evidence as well as an ellipse. In particular, Mars just didn't quite seem to fit a circular orbit and that is what led Kepler to describe the orbits of the planets as elliptical (Mars has one of the most eccentric orbits of any planet, making it one of the easiest to observe the eccentricity) And not too long (relative to the gap between Hypatia and Kepler) after Kepler, Newton was able to come along and provide us with a mathematical model to explain (to the extent he could, given the data available) the interaction between masses.

So, it is a bit of a hard sell to claim that Hypatia would have reasonably described the motion of the planets as elliptical (because her instruments would have lacked the precision of Kepler's) and doubly hard to believe that, had she actually come to such a conclusion, she would then go on to theorize that this would explain the seasons because the relationship between the earth's tilt and the seasons was actually much more readily observed at the time than the "not quite circular" orbits of the earth around the sun.