To test copernicus’s model, tycho took meticulous measurements of the positions of the planets, and he hired kepler to interpret the data. kepler found that the geocentric model did not accurately predict the planets’ positions, but neither did copernicus’s heliocentric model. he found that copernicus’s insistence that the planets’ orbits were perfectly circular was the problem. if the orbits were instead ellipses, then the heliocentric model would have been able to very accurately predict the positions of the planets. this is known as kepler’s first law of planetary motion.

choose one or more:

a. elliptical orbits cause a planet to sometimes be closer to and sometimes farther away from the sun.

b. the sun is located at one focus of a planet’s elliptical orbit, and the planet is located at the other focus.

c. halley’s comet has a highly eccentric orbit.

d. the sun is located at the center of a planet’s elliptical orbit.

e. the eccentricity of mars’s orbit is zero.