4. Which did Kepler notice about planetary motion that caused him to propose Kepler's first law of orbital motion?
O The planets have circular orbits.
O The distance between Mars and the sun is constant.
O The distance to the sun varies.
O Most planets have highly elliptical orbits.
Kepler noticed that most planets have highly elliptical orbits, which led him to propose Kepler's first law of orbital motion.
Kepler noticed that the distance between a planet and the sun varies, which led him to propose Kepler's first law of orbital motion. To understand this, Kepler made very precise observations of the positions of the planets in the sky over a long period of time.
To verify this yourself, you could study Kepler's observations and calculations, which are recorded in his book titled "Astronomia Nova" (New Astronomy). In this book, he presented his findings, including his discovery that the path of a planet around the sun is not a perfect circle, but rather an ellipse.
Kepler studied the motions of various planets, focusing particularly on Mars. Through careful observation, he identified that the distance between Mars and the sun is not constant, but instead changes as Mars orbits around the sun. This led him to conclude that the shape of the planetary orbits is not circular, as was commonly believed at the time, but elliptical.
As a result, Kepler proposed his first law of orbital motion, also known as the law of ellipses. This law states that the path followed by a planet around the sun is an ellipse, with the sun located at one of the foci of the ellipse. In simpler terms, a planet doesn't always travel at the same distance from the sun throughout its entire orbit.
Therefore, the correct answer to your question is: The distance to the sun varies.