Astronomer — Ole Christensen Rømer (1644–1710) was a Danish astronomer, born in Aarhus and active for years at the Paris Observatory. In 1676, studying the timing of the eclipses of Jupiter’s moon Io, he observed that these appeared early or delayed depending on whether the Earth was approaching or receding from Jupiter. He deduced that light takes a finite time to propagate and provided the first quantitative estimate of its speed, demonstrating that it is not infinite. It was a fundamental turning point, since until then many believed the propagation of light to be instantaneous. Rømer was also a skilled inventor of astronomical instruments and introduced important reforms of weights, measures and the calendar in Denmark.
Fun fact
His estimate of the speed of light, though imprecise by modern standards, showed for the first time that light does not travel instantaneously, against the prevailing view held by Descartes.
Theories and contributions
- Finite speed of light — From the variations in the timing of Io’s eclipses he deduced that light propagates at a finite speed, providing the first quantitative estimate of it.
Present in chapters
Linked atoms
1 linked atom.