1609 (Astronomia nova published) / Europe
Kepler tests elliptical orbits against observations
Using Tycho Brahe's Mars observations, Kepler replaces uniform circular orbits with ellipses and the equal-area relation.
The story
Astronomia nova presents what became the first two laws: elliptical orbits and equal areas swept in equal times. Orbital speed therefore varies. The third law appeared in 1619, not 1609. Prague represents the research setting; the achievement depended on Tycho's observations, extensive calculation and repeated revision.
Connections and context
Newton later gave a dynamical account of these relationships. Observational regularities can constrain a theory without being the same kind of explanation.
Dates and precision
1609 (Astronomia nova published) Documented date
Positioned by the documented year, month or day. Missing precision is not inferred.
Representative map location
Prague (research)
Kepler's city for analysing Tycho's data; Astronomia nova was printed in Heidelberg.
Representative coordinates · 50.08°, 14.42°
A marker identifies one representative place, such as a manuscript collection, laboratory or observing site. It does not mean the work happened only there, or assign a shared discovery to one country.
Bibliography
- NASA | Orbits and Kepler's laws
- NASA Glenn Research Center | Kepler's Laws
References are listed as plain bibliography titles. They support particular facts or context; a reference does not certify every interpretation in a story.