# I Hypatia, Elliptic orbits, conic sections

#### JTC

I understand that Hypatia proposed elliptic orbits.
I also understand she studied conic sections.
And, of course, one of the intersections of an inclined plane through a cone is elliptical.

So now my question: if she did propose elliptic orbits (not interested in who may also have done it), what motivated her? If it was a result of her study of conic sections, then what is it about conic sections that compelled her to extend it to planetary orbits?

With Kepler, et. al. we can see his three laws of planetary motion, etc, ounded in mathematics. But what drove Hypatia? All I can envision is a leap from conic sections to orbits, but I cannot see how she made the leap. Or was it just a lucky guess?

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#### phyzguy

With Kepler, et. al. we can see it was re-derivations and applications of Newton's work.
I don't know the answer to your main question, but what do you mean by this? Kepler died before Newton was born.

#### Janus

Staff Emeritus
Gold Member
With Kepler, et. al. we can see it was re-derivations and applications of Newton's work. But what drove Hypatia? All I can envision is a leap from conic sections to orbits, but I cannot see how she made the leap. Or was it just a lucky guess?
As already pointed out, Kelper's laws came before Newton. Kepler law's were based on careful measurement of the planets. He observed that planets followed certain rules as they orbited the Sun. Newton later came along to give a theoretical basis for these observations Kepler made about planetary motion.

#### JTC

As already pointed out, Kelper's laws came before Newton. Kepler law's were based on careful measurement of the planets. He observed that planets followed certain rules as they orbited the Sun. Newton later came along to give a theoretical basis for these observations Kepler made about planetary motion.
Yes, sorry about that. I had this in my head --and conflated it over the three laws of each -- and did not even think before posting. I have corrected the post, since that was not the point; and I don't want the original question hijacked. Sorry.

#### mfig

What is your source for the claim that Hypatia proposed elliptical orbits? I have not seen this one!

#### JTC

What is your source for the claim that Hypatia proposed elliptical orbits? I have not seen this one!
I do not recall. I know I read it somewhere. Are you suggesting I am wrong? If so, I would like to know. I really thought she had proposed elliptical orbits.

#### Ibix

This page http://historybooksreview.co.uk/what-did-hypatia-know-science-of-agora/ suggests the claim is from a movie, and describes it as a "bold assertion". It does note that it's plausible that she had access to information and techniques that would have allowed her to deduce that orbits were ellipses, but says there are no surviving primary sources.

I'm not in a position to comment on the veracity of any of this.

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