Origins of the Ptolemaic System
We’ve worked backwards from Kepler to Ptolemy. What inspired Ptolemy and his predecessors (Apollonius and Hipparchus) to come up with this scheme in the first place?
Category Archives: History
From Kepler to Ptolemy 4
Speed Laws
In Ptolemy’s system, the point on the deferent moves uniformly as viewed from a point called the equant point, or sometimes just equant. The equant, the center of the deferent, and Earth all lie in a straight line, with the center midway between Earth and the equant.
Set Theory Jottings 2. Cantor’s Paradise
Cantor’s Paradise
No one shall expel us from the Paradise that Cantor has created for us.
—Hilbert, “Über das Unendliche” [On the Infinite], in Mathematische Annalen 95 (1925)
I used to believe these myths about the history of set theory:
Filed under History, Set Theory
From Kepler to Ptolemy 2
I’ll begin with Kepler’s first two laws, and work backwards to Ptolemy’s system. Seeing Keplerian astronomy recast this way will expose the bones of the Ptolemaic system.
Deferents and Epicycles
From Kepler to Ptolemy 1
Quite some time ago I started writing up notes, for my own amusement, on the history of astronomy. I’ve worked on it on-an-off over the years, but there always seems to be a bit more I should add. Eventually the pdf version will be ready for prime time. Meanwhile I’ve decided to convert what I have into a series of posts. Enjoy!
Eminent Victorians
Filed under History Book Club
Akira Kurosawa
Still from Ikiru
Another post from the History Book Club, based on:
- The Films of Akira Kurosawa, by Donald Richie
- The Warrior’s Camera: The Cinema of Akira Kurosawa, by Stephen Price
- Something Like an Autobiography, by Akira Kurosawa.
- Commentary tracks in the Criterion Collection
Filed under History, History Book Club
The Peloponnesian War
Another post from the History Book Club.
Donald Kagan: Ancient Greek History; The Peloponnesian War
Filed under History, History Book Club
The Monoenergetic Heresy (Part 2)
In Part 1, I mentioned my (momentary) discombobulation when I learned about the 6th century Monoenergetic Heresy—long before ‘energy’ entered the physics lexicon. What’s going on? But as I said, “Of course you know the answer: Aristotle.”
Over the years, I’ve dipped in Aristotle’s works several times. Caveat: I’m a dilettante here. Or to borrow the disclaimer that used to grace horoscope columns, what follows is “for entertainment purposes only”.
Aristotle, Weight Loss Guru Continue reading
Filed under Aristotle, Bagatelles, History
Diagonal Argument 