🪐W4 L1 - Explaining patterns - Paths of planets - orbits and Kepler's Laws Flashcards
Learn how humans developed their understanding of the Solar System and planetary motion.
What was the orginal meaning of the word planet?
Wanderer
Who was the first to suggest a heliocentric model?
Aristarchus of Samos
What did Ptolemy suggest was at the centre of the universe?
The earth
Which Polish astronomer re-introduced heliocentrism in the 1500s?
Nicolaus Copernicus
Which Danish astronomer took very accurate planetary movement measurements in the 1500s?
Tycho Brahe
What solar system model did Tycho Brahe propose?
Geo-heliocentric model
How many foci does an ellipse have?
Two
What is the long axis in an ellipse called?
The major axis
What is the semimajor axis of an ellipse?
The radius of the ellipse from midway along the major axis line
What does eccentricity describe?
How stretched an elipse is
What does eccentricity of 0 describe?
A perfect circle
What is Kepler’s first law?
Planets orbit in an elipse with the sun at one focus
tick on the 1 is the start of an ellipse, and the base is on fire because the sun is on it
What is Kepler’s second law?
As a planet moves around its orbit it sweeps out equal areas in equal times
(Start of the 2 is a planet orbiting; the diagonal joining the base forms an A which stands for area, and line end of the 2 is the arm of a watch indicating time)
What impact on orbital speed does Kepler’s second law have?
Orbital speed is not constant
What is Kepler’s third law?
The further a body is from the sun, the longer its orbital period.
(top of 3 is a small circle, bottom is a larger circle, with clock hands in the lower circle indicating takes longer for a bigger orbit)
