8.1 Lectures
151
Fig. 8.1 Jan Hendrik Oort and his at that time fiancée Johanna Maria (Mieke) Graadt van
Roggen at the dinner after defending his dissertation and obtaining his Ph.D. degree
in Groningen on May 1, 1926. They married on May 24, 1927. From the Oort Archives
When in 1917, at the age of 17, I began my studies in Groningen I became
almost immediately inspired by Kapteyn’s lectures on elementary astronomy. Although I had been strongly interested in astronomy since my high school years,
and this influenced my choice of the University of Groningen because Kapteyn
was there, I was in 1917, still undecided between physics and astronomy as my
major direction; I remember that I was so impressed by the way he taught elementary celestial mechanics that I tried to convey my new insights to friends
who had likewise entered the University, but were studying humanities. But I
do not believe that I succeeded in conferring to them a full appreciation of the
fascination of celestial mechanics.
Perhaps the most significant thing I learned –mainly, I believe from Kapteyn’s
discussion of Kepler’s method of studying nature– was to tie interpretation directly to observations, and to be extremely wary of hypotheses and speculations.
In the first part of his course, Kapteyn refrained, for instance, from introducing
the notion of ‘force’ to replace the measurable quantity ‘acceleration’. His disliked
intricate mathematical formulations which prevented one from ‘seeing through’
a theory; he feared the danger that the formulae might make one lose sight of
151
Fig. 8.1 Jan Hendrik Oort and his at that time fiancée Johanna Maria (Mieke) Graadt van
Roggen at the dinner after defending his dissertation and obtaining his Ph.D. degree
in Groningen on May 1, 1926. They married on May 24, 1927. From the Oort Archives
When in 1917, at the age of 17, I began my studies in Groningen I became
almost immediately inspired by Kapteyn’s lectures on elementary astronomy. Although I had been strongly interested in astronomy since my high school years,
and this influenced my choice of the University of Groningen because Kapteyn
was there, I was in 1917, still undecided between physics and astronomy as my
major direction; I remember that I was so impressed by the way he taught elementary celestial mechanics that I tried to convey my new insights to friends
who had likewise entered the University, but were studying humanities. But I
do not believe that I succeeded in conferring to them a full appreciation of the
fascination of celestial mechanics.
Perhaps the most significant thing I learned –mainly, I believe from Kapteyn’s
discussion of Kepler’s method of studying nature– was to tie interpretation directly to observations, and to be extremely wary of hypotheses and speculations.
In the first part of his course, Kapteyn refrained, for instance, from introducing
the notion of ‘force’ to replace the measurable quantity ‘acceleration’. His disliked
intricate mathematical formulations which prevented one from ‘seeing through’
a theory; he feared the danger that the formulae might make one lose sight of