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42 Cards in this Set

  • Front
  • Back
a small circle the center of which moves around in the circumference of a larger circle: used in Ptolemaic astronomy to account for observed periodic irregularities in planetary motions.
Who discovered the "heliocentric universe"?
What does a "Geocentric Universe" mean?
It means that people used to think that the Earth was the center of the solar system and that everything revolved around it.
occurs when the two planets lie in a line on the same side of the Sun
inferior conjunction
angle btwn the sun and a planet as viewed from the Earth
length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation.
synodic period
variation (change) in anle that occurs when viewing a nearby object from different places.
The orbit of every planet is an ellipse with the sun at one of the foci.
Kepler's 1st law of planetary motion
A line joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit. This means that the planet travels faster while close to the sun and slows down when it is farther from the sun.
Kepler's 2nd law of planetary motion
The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes (the "half-length" of the ellipse) of their orbits.
Kepler's 3rd law of planetary motion
The distance from us and the Sun is an ___________ _________.
astronomical universe
distance light travels in one year
light year
an object in motion stays in motion

Newton's 1st law of motion
The acceleration of an object is proportional to the force acting on it

Force = Mass * Acceleration
Newton's 2nd law of motion
The ancient Greeks laid the groundwork for progress in science. Early Greek astronomers devised a geocentric cosmology, which placed the _______ at the center of the universe.
The _________ method is a procedure for formulating theories that correctly predict how the universe behaves.
A scientific theory must be testable, that is, capable of being _________.
Theories are tested and verified by observation or __________ and result in a process that often leads to their refinement or replacement and to the progress of science.
In a heliocentric cosmology, the ______ is but one of several planets that orbit the sun.
The _______ orbital period of a planet is measured with respect to the stars. It determines the length of the planets year. Its ________ period is measured with respect to the sun as seen from the moving Earth.
_______ describe the paths of the planets around the Sun much more accurately than do circles.
The invention of the telescope led ________ to new discoveries, such as the phases of Venus and the moons of Jupiter, that supported a heliocentric view of the universe.
_______ based his explanation of the universe on three assumptions now called ________ laws of motion. These laws and his law of universal gravitation can be used to deduce Kepler's laws and to describe planetary motion with extreme accuracy
The _____ of an object is a measure of the amount of matter in the object.
______ is a measure of the force with which the gravity of some other object pull on the object's mass when the two objects are at rest with respect to each other.
What makes a theory scientific?
A theory is an idea or set of ideas proposed to explain something about the natural world. A theory is scientific if it makes predictions that can be objectively tested and potentially disaproved.
What is the shape of the Earth's orbit around the Sun?
All planets have elliptical orbits around the Sun.
Do the planet orbit the Sun at constant speeds?
No. The closer a planet is to the Sun in its orbit, the faster it is moving. It moves fastest at perihelion and slowest at aphelion.
Do all the planets orbit the Sun at the same speed?
No. A planet's speed depends on its average distance from the Sun. The closest planet moves fastest, the most distant planet moves slowest.
How much force does it take to keep an object moving in a straight line at a constant speed?
Unless an object is subject to an outside force, like friction, it takes no force at all to keep it moving in a straight line at a constant speed.
How does an object's mass differ when measured on Earth and on the Moon?
Assuming the object doesn't shed or collect pieces, its mass remains constant whether on the Earth or on the Moon. Its weight, however, is less on the Moon.
Who wrote down the equation for the law of gravitation?

a. Copernicus
b. Brahe
c. Newton
d. Galileo
e. Kepler
c. Newton
Which of the following most accurately describes the shape of the Earth's orbit around the Sun?

a. circle
b. ellipse
c. parabola
d. hyperbola
e. square
b. ellipse
Of the following planet's, which takes longest to orbit the Sun?

a. Earth
b. Uranus
c. Mercury
d. Jupiter
e. Venus
b. uranus
What is a sun-centered model of the solar system called?
How long does it take the Earth to complete a sidereal orbit of the Sun?
365 and 1/4 days
How did Copernicus explain the retrograde motions of the planets?
The Copernican model placed the Sun at the center of the universe and the Earth and planets in orbit around the Sun. Retrograde motion is an optical illusion caused by our moving point of view. The outer planets have larger orbits than Earth, so the Earth overtakes, causing the planet to appear to move backward. The inner planets have smaller orbits than Earth, so when they overtake us, they appear to move backwards.
Which planets can never be seen at opposition?
inferior planets
Which planets never pass through inferior conjunction?
superior planets
At what configuration would it be best to observe Mars, Jupiter, and Saturn with an Earth-based telescope?
Superior conjunction
At what configuration would it be best to observe Mercury or Venus with an Earth-based telescope?
Inferior conjunction
Why was the discovery of Neptune a major confirmation of Newton's universal law of gravitation?
Because he predicted that there was an 8th planet out there.