E Mich Physics - Ancient Ideas Flashcards
Geocentrism
The belief that the Earth was at the centre of the universe
Who proposed the idea of geocentrism?
Aristotle
When was Aristotle’s geocentrism proposed?
350 BC
Heliocentrism
The belief that the Sun is at the centre of the universe
Who proposed the idea of heliocentrism?
Nicolaus Copernicus
Book where Nicolaus Copernicus presented Heliocentrism
On the Revolutions of Celestial Spheres (1543)
Who provided evidence supporting heliocentrism?
Galileo Gallilei
What three pieces of evidence did Galileo provide to support heliocentrism?
Phases of Venus
Moons of Jupiter
Texture of the Moon
Who proposed the idea of retrograde motion?
Ptolemy
Retrograde Motion
When outer planets appear to move backwards due to the motion of the Earth around the Sun
Epicycle
The smaller circular orbit a planet moves in along a deferent
Deferent
The larger circular orbit along which the epicycle moves
When was Ptolemy’s Retrograde Motion explained?
150BC
Who developed a method to calculate the diameter of the Earth?
Eratosthenes
How was the diameter of the Earth determined?
Eratosthenes calculated angle between Alexandria and Syene to be about 7.2° using the shadows of 2 sticks. He used this to calculate the circumference of the Earth by multiplying the distance by 50. Then he divided the circumference by π.
When was Eratosthenes’ method for calculating the diameter of the Earth discovered?
250 BC
Kepler’s First Law
Orbits are elliptical with the star as the focus
Kepler’s Second Law
A planet covers the same amount of space in the same amount of time, no matter where it is in the orbit
Kepler’s Third Law
A planet’s orbital period is proportional to the size of its orbit
Time Period² is proportional to Orbital Radius³
Brahe’s beliefs
The Sun and Moon orbit the Earth and everything else orbits the Sun
Equation for circular orbits
v = 2πr / t
Eccentricity
How much an elipse deviates from a perfect circle
Eccentricity of planetary orbits
Low
Eccentricity of comet orbits
High
Foci
(Plural of focus) The 2 points within an ellipse that define its shape
