Aristotle
proposed the geocentric view that was accepted and used for more than 18 centuries
Copernicus
proposed heliocentric model
Reasons Copernicus proposed the heliocentric model
it was much simpler than the Ptolemaic model
Ptolemiac theory of Retrograde Motion
Planets orbit in small circles called epicycles, and the epicycle is orbiting the Earth in a larger orbit called a deferent. This caused the planet to have a "looping" motion as seen from Earth.
Epicycles
small circles planets orbit in
Copernican theory of Retrograde Motion
Planets orbit the Sun at different speeds. When an inner, faster-moving planet "passes" a slower outer one, the slower planet appears to move backwards.
Retrograde Motion
the phenomenon in which the apparent motion of the superior planets sometimes reverses
Galilean Discoveries
The shape of a planet's orbit is an ellipse; the Moon has mountains, valleys, and craters; the Sun has spots and rotates; telescopes.
Galilean observations of the phases of Venus
showed that Venus had to orbit the Sun and not the Earth
Focus of the moon's orbit
where earth is located
Kepler's Second Law
Jupiter will be traveling most slowly around the sun when at aphelion; Pluto will be traveling fastest around the sun when at perihelion
Ellipse
the shape of earth's orbit around the sun
Eccentricity
the extent to which Mars' orbit differs from a perfect circle
Kepler's Third Law
p^2 = a^3
How does orbital speed at aphelion compare to the speed at perihelion?
Lower
Kepler's second law of planetary motion states that a planet in orbit around the Sun will...?
Sweep out equal areas in equal times
Tycho Brahe
amassed a large number of precise measurements of stellar and planetary positions in the sky
The speed of a planet orbiting the Sun is independent of the planet's position in its orbit.
false
Astronomical Unit (AU)
the distance the Earth travels in its orbit in one year.
A calculation of how long it takes a planet to orbit the Sun would be most closely related to Kepler's
Third Law of Planetary Motion
According to Newton's second law of motion
the Moon has a larger acceleration than Earth, because it has a smaller mass
Newton's Laws of Motion
The acceleration of an object is directly proportional to the net applied force and inversely proportional to the object's mass; to every action there is an equal and opposite reaction; an object at rest remains at rest, and a moving object continues to m
During retrograde motion, planets actually stop and move backwards in space.
false
Geocentric View
earth lies at the center of the universe and all other bodies move around it
epicycle
part of the geocentric view, planets move uniformly in a small circle whose center moved uniformly around Earth on a second and larger circle (the deferent)
deferent
the larger circle on which epicycle centers move; geocentric view
Ptolemiac Model
geocentric model; Claudius Ptolemy, predicted with great accuracy the positions of the then-known planets
Aristarchus
first to suggest heliocentric view
Eratosthenes
accurately determined the size of the earth
Heliocentric View
all bodies move around the sun; copernicus
Copernicus
introduced the heliocentric view
Galileo
discovered that the moon has mountains, valleys, and craters; the sun has imperfections (sunspots) and rotates; Jupiter has four moons; Venus has phases similar to our moon - all supported heliocentric view
Kepler
summarized the motions of all the known planets in three laws of planetary motion
Kepler's first law of planetary motion
The orbital paths of the planets are elliptical (not circular) with the sun at one focus
Kepler's second law of planetary motion
An imaginary line connecting the sun to any planet sweeps out equal areas of the ellipse in equal intervals of time
Kepler's third law of planetary motion
the square of a planet's orbital period is proportional to the cube of its semimajor axis
perihelion
a planet's closest point of approach to the sun
aphelion
a planet's greatest distance from the sun
Brahe
Last astronomer without a telescope. Provided Kepler with the data needed in order to develop his three Laws
Law of Inertia
A body remains at rest, or moves in a straight line (at a constant velocity), unless acted upon by a net outside force.
F=ma
The acceleration of an object is proportional to the force acting upon it.
Law of Reciprocal Actions
For every action, there is an equal and opposite reaction.