The Sun
Category Archives: History
From Kepler to Ptolemy 7
The Full Ptolemy
We now start the second part of this series: an in-depth look at the Ptolemaic system.
Set Theory Jottings 3. The Paradoxes
Frege added an appendix to volume II of his 1903 magnum opus Grundgesetze der Arithmetik (Foundations of Arithmetic). It began:
A scientist can hardly meet with anything more undesirable than to have the foundations give way just as the work is finished. I was put in this position by a letter from Mr. Bertrand Russell when the work was nearly through the press.
Filed under History, Set Theory
From Kepler to Ptolemy 5
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?
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!
Diagonal Argument 