NATS 1740: EXAM NOTES

LECTURE 11: Kepler's Third Law - More distant planets orbit the Sun at slower average speeds, obeying the relationship. p^2 = a^3 p = orbital period in years; a = average distance from the Sun in AU To calculate orbital period: a^3 then sqrt() your result of a^3 or in other words, p = √(a^3) LECTURE 12: Galileo overcame major objections to the Copernican view. Three key objections rooted in the Aristotelian view were the following: 1. Earth could not be moving because objects in air would be left behind 2. Non circular objects are not "perfect" as heavens should be. 3. If Earth were really orbiting Sun, we'd detect stellar parallax. Overcoming the first objection: - Galileo's experiments showed that objects in air would stay with a moving Earth - Aristotle thought that all objects naturally come to rest. - Galileo showed that objects will stay in motion unless a force acts to slow them down (Newton's first law of motion)