Chapter 3 Flashcards
In Ptolemy’s model, it is possible to have a planetary orbit without retrograde motion
true
Copernicus’ heliocentric model was able to predict the location of the planets more accurately than Ptolemy’s geocentric model
false
Copernicus was the first to be able to prove that the Earth orbited around the Sun
false
According to the small angle equation, if an object at a fixed distance is suddenly shrunk to a smaller size, then the angular size will
decrease
Copernicus was the first person to suggest that the Sun is at the center of our solar system.
false
Copernicus figure out which planets were closer to the Sun and which were further
sidereal and synodic periods
Eratosthenes
ancient astronomer measured the radius of the Earth
size of the Earth could be measured accurately in ancient times by using
shadows on Earth
Ptolemy improved the geocentric model by
adding epicycles and deferents
One of the main objections to the heliocentric model
we do not feel the Earth moving
Aristotle believed that the planets
orbited the Earth in circular orbits
superiod conjunction
When a planet orbits to the opposite side of the Sun as Earth (and it appears near the Sun in our sky), the planet is at
sidereal period
The time it takes a planet to orbit the Sun once and return to the same location in space
Ptolemy’s improvements were important because they explained
retrograde motion
scientific ideas was never discussed in the ancient world
faint lights in the sky are galaxies
Aristotle
believed the universe could be understood by the power of reason alone
Geocentric cosmology
all other celestial bodies travel around the earth in circular orbits
Small angle equation
θ = 206,265 * D / d
D
diameter
d
distance
θ
angular diameter
distance equation
d=206,265*D/θ
diameter equation
D=θ*d/206,265
Retrograde motion
some planets can reverse their steady eastward motions among the stars
Ptolemaic model
requires the planets not only to move in circles around the Earth but also to move along smaller circles around imaginary points along the main circular orbits
Epicycles
circle that is carried and rides around on another circle
Epicycles
circle that is carried and rides around on another circle
Heliocentric model
relative spacing of planets is fixed uniquely by their apparent motions
Parallax
shift in angle that occurs when a nearby object is seen against a distance backdrop from two different perspectives
Elongation
angle between the sun and a planet as seen by an observer on earth
inferior planets
planets closer to the sun than the earth
superior planets
planets further from the sun than the earth
greatest elongation
inferior planets limit
inferior conjunction
planet is between the sun and the earth
superior conjunction
planet is on the other side of the sun as seen from earth
opposition
elongation is 180 degrees
synodic period
time it takes for a planet to make a complete cycle of elongation configuration
sidereal period
time it takes for a planet to complete an orbit
superior planets equation
1/S=1/E-1/P
inferior planets equation
1/S=1/P-1/E
E
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