Astronomy
the science that studies the Universe
Geocentric
Earth was a sphere that stayed motionless at the center
Orbit
an object as it goes around another object in space
Heliocentric
sun-centered universe
Retrograde Motion
the apparent westward drift
Elipse
the oval shaped path Mars goes around the sun
Astronomical Unit (AU)
average distance between Earth and the Sun
Rotation
turning, or spinning of a body on an axis
Revolution
the motion of a body along it's orbit
Precession
slight movement over a period of 26,000 years of Earth's axis
Perihelion
the point in the orbit of a planet is closest to the sun
Aphelion
the point in the orbit of a planet is farthest from the sun
Perigee
moon is closest to Earth
Apogee
moon is farthest from Earth
Phases of the Moon
a change in the amount of the moon that appears lit
Solar Eclipse
when the moon moves directly in front of the sun, it casts a dark shadow on Earth
Lunar Eclipse
when it moves within Earth's shadow
Crater
round depressions in the surface of the moon
Ray
splash mark that radiate outward for hundreds of kilometers
Mare
smooth areas of the moon
Rilles
look like valleys or trenches, long channel associated with lunar maria
Lunar Regolith
a thin, grey layer on the surface of the moon, consisting of loosely compacted fragmented material
What planet was unknown to the ancient Greeks?
Uranus
Why did Aristotle concluded that the Earth was round?
it always casts a curved shadow during a lunar eclipse
What was the Ptolemaic model of the universe?
Earth was the center of the universe
One AU averages out to what number?
150 million kilometers
What is the force that gravity exerts on an object?
weight
How old are the lunar highlands?
4.5 billion years old
What was not discovered by Galileo?
the 2 moons of Mars
What movement of Earth is responsible for night & day?
rotation
What is Earth's orbital speed?
107,000 kilometers per hour
The number of eclipses each year does not go above what?
7
What is the moon doing when it is changing from new to full?
waxing
How long does it take the moon to go from a full moon to a new moon?
2 weeks
What formed the Maria?
basaltic lava
How did the maria on the moon's surface form?
asteroids punctured the surface letting magma bleed out
How does crater density relate to the moon's geologic history?
high crater density is associated with older surfaces
A discovery that led to the modern view of the solar system was that the orbit of the planets are?
ellipses
Axial Precession
A very slow motion of the Earth's axis that requires 26,000 years to complete
Synodic month
period of time required for the moon to complete one cycle of phases
What type of eclipse can only occur during a new-moon phase?
solar eclipse
What is the giant-impact hypothesis?
Collision between a body the size of Mars and Earth created the moon
List the 3 phases in which the moon evolved from oldest to youngest?
-Highlands
-Maria
-Regolith
Why have old craters in the moon not been erased as similar craters on Earth have been?
there is no atmosphere on the moon
What must happen in order for an eclipse to take place?
the moons orbit must cross the plane of the ecliptic
Who can see a total eclipse of the moon when it occurs?
anyone observing in the region
What are the 3 laws of Planetary Motion?
1. All planets move about the Sun in elliptical orbits
2. A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time
3. the sidereal periods of the planets are directly proportional to the cubes of their mean distances from the Sun
