Which did Kepler notice FIRST about planetary motion that caused him to propose Kepler’s first law of orbital motion? * 1 point The planets have circular orbits. The distance between Mars and the sun is constant. The planets speed up and slow down but cover the same area. Most planets have highly elliptical orbits.
The planets speed up and slow down but cover the same area.
The correct answer is: The planets speed up and slow down but cover the same area.
Kepler noticed that the planets speed up and slow down but cover the same area. This observation led him to propose Kepler's first law of orbital motion. To understand how Kepler arrived at this conclusion, let me explain the steps he followed:
1. Data Collection: Kepler meticulously gathered and analyzed astronomical data, specifically the observations made by his predecessor, Tycho Brahe. These data included precise measurements of the positions and movements of planets over time.
2. Analysis of Planetary Motion: While studying the motion of planets, Kepler noticed that their orbital speeds varied as they moved around the Sun. Some planets appeared to move faster when they were closer to the Sun and slower when they were farther away.
3. The "Area Law": In his analysis, Kepler found that the time a planet takes to sweep out a specific area of its elliptical orbit is constant. This means that if you draw a line connecting a planet to the Sun, the planet will sweep out equal areas in equal periods of time.
4. Conclusion: Based on his observations and calculations, Kepler proposed his first law of orbital motion. He stated that the planets move in elliptical orbits with the Sun located at one of the focal points of the ellipse. This law explained why the planets speed up and slow down but cover the same area: they move faster when closer to the Sun, covering more area, and slower when farther away, covering less area.
Therefore, the correct answer is "The planets speed up and slow down but cover the same area." This was the first aspect of planetary motion that Kepler noticed, leading him to propose his first law of orbital motion.