What Kepler and Newton really did.  This has been a good week[1]
for people getting the history of astronomy in the seventeenth
century wrong. Darin Hayton drew my attention to what is
basically a rather good article by John O’Neil in the New York
Times on the equation of time and the difference between local
time measured by the sun and standard time measured by the
clock. The article is just fine except for one sentence that
instantly awoke the Histsci Hulk in me.  The author wrote:  The
changes in the solar time follow a different cycle. In the early
1600s Kepler discovered that planets move faster at the part of
their orbit that is closest to the sun, the perihelion. For
Earth, perihelion comes a little after the winter solstice, so
from November on, Earth is accelerating. [my emphasis]  Kepler
didn’t discover that planets (actually in the case under
discussion the sun) move faster in some part of their orbits he
suggested a new, and as it turned out correct, solution to
explain the differences in speed i