When Johannes Kepler proposed a new model of the solar system in the early 1600s, it was a revolutionary idea. The model addressed many of the problems with earlier circular-orbit models, and greatly simplified the calculation of planetary motions. Still, the model was so radical that it wasn’t fully accepted until Newton was able to derive the model from his law of universal gravitation. What made Kepler’s model so powerful is that is required only three simple rules, which we now call Kepler’s laws.
Kepler’s Hypothesis
One of the common misconceptions presented in science is that it occurs in revolutionary steps. For example, the idea that Copernicus developed the heliocentric (sun-centered) model of the solar system, then Kepler showed that planets moved in ellipses and introduced Kepler’s laws, then Newton introduced the law of gravity that proved Kepler’s laws to be true. Each revolutionary idea replacing the previous one. But the real history is not quite so clean. Take for instance the development of Kepler’s laws.
Mutual Attraction
The first known binary stars were observed in the 1800s, but it wasn’t until the 1900s with the introduction of the filar micrometer that decently accurate measurements could be made. This device allowed you to center your telescope on the primary star, and then measure the position of the secondary star relative to the primary. By taking measurements over time (sometimes years or decades) you can start to see the companion star trace its path.
More Massive Evidence
Related to my previous post, if you’d like to se an animation of the central S-stars, check out this video.
Massive Evidence
In the center of our galaxy is a supermassive black hole. We can see stars orbiting it, so we know just how massive it is.