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75 Cards in this Set
- Front
- Back
A large glowing ball of gas that generates heat and light through nuclear fusion.
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star
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A moderately large object that orbits a star; it shines by reflected light and its composition may be rocky, icy, or gaseous.
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planet
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An object that orbits a planet.
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moon (or satellite)
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A relatively small and rocky object that orbits a star.
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asteroid
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A relatively small and icy object that orbits a star.
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comet
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A star and all the material that orbits it, including its planets and moons.
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solar system (star system)
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An interstellar cloud of gas and/or dust.
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nebula
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A great island of stars in space, all held together by gravity and orbiting a common center.
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galaxy
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The sum total of all matter and energy; that is, everything within and between all galaxies.
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universe
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A transparent globe around the Earth where the Sun, Moon, and stars appear.
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Celestial Sphere
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Position north or south of the equator.
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latitude
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Position east or west of the prime meridian.
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longitude
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Projections of the Earth's north and south poles onto the celestial sphere.
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Celestial poles
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Projection of the Earth's equator onto the celestial sphere.
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Celestial equator
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Point directly overhead.
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zenith
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Marks the intersection of the Earth an sky.
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horizon
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Angular height above the horizon.
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altitude
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Line through the zenith, connecting North and South on horizon.
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meridian
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Why do stars rise and set?
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Earth rotates west to east on its axis, so stars appear to circle from east to west about the celestial poles.
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Stars near a celestial pole that never "set".
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circumpolar stars
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Why don't we see the same constellations throughout the year?
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The constellations we see vary with latitude and the time of year because the Earth orbits the Sun.
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The path the sun seems to take eastward along the celestial sphere.
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ecliptic
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Why do we see different stars at night throughout the year?
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The night sky is opposite the Sun and as we go around the Sun, the direction of "night" changes.
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What causes the seasons?
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The tilt of the Earth's rotation axis. Sunlight is either concentrated or spread out along each hemisphere at different times of the year.
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The highest path of the Sun; it rises and sets at the most extreme north of due east.
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summer solstice
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The lowest path of the Sun; it rises and sets at the most extreme south of due east.
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winter solstice
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When the ecliptic crosses the celestial equator; Sun rises precisely due east and sets precisely due west.
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equinoxes
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The "wobble" of the Earth's axis.
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precession
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Why do we only see one face of the Moon?
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The Moon has a synchronous orbit and its rotation period equals its orbital period, so we always see the same face of the Moon.
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What causes eclipses?
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When the Earth or Moon passes through the others shadow.
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How do lunar eclipses occur?
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They occur when the Moon passes into the Earth's shadow; it can only happen at a FULL MOON and can be penumbral, partial, or total.
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How does a solar eclipse occur?
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They occur when the Moon's shadow falls directly on the Earth; it can only happen at a NEW MOON and can only be totally visible on part of the Earth.
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When the moon only partially blocks the Sun.
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partial eclipse
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When the Moon completely blocks the Sun.
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total eclipse
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When the moon is too small in the sky to completely block the sun.
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annular eclipse
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Why don't we have an eclipse at every new and full moon?
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The Moon's orbit is tilted 5 degrees to the ecliptic plane and the Moon must be close to the ecliptic for an eclipse to occur.
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What are the two conditions that need to be met for there to be an eclipse?
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1) It must be a full moo (lunar) or new moon (solar).
2) The Moon must be at or near one of the two points in its orbit ("nodes") where it crosses the ecliptic. |
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Explain retrograde motion.
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Apparent retrograde motion occurs when we "lap" another planet (or it laps us). The planets do not actually move backwards.
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Why do we see moon phases?
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We see moon phases because we observe some combination of the day and night sides of the moon.
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What did ancient civilizations achieve in astronomy?
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Ancient civilizations kept track of time and seasons, monitored lunar cycles, planets and stars, predicted eclipses, and aided in navigation.
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How did the Greeks explain planetary motion?
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They made models placing the Earth at the center of the universe and claimed that the Heavens must be "perfect" and so objects orbited the Earth in perfect spheres or in perfect circles.
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The apparent change in the location of an object due to the difference in location of the observer.
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parallax
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What is Kepler's First Law of Planetary Motion?
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The orbit of each planet around the Sun is an ellipse with the Sun at one focus.
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What is Kepler's Second Law of Planetary Motion?
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As a planet moves around its orbit, it sweeps out equal areas in equal times. A planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
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What is Kepler's Third Law of Planetary Motion?
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More distant planets orbit the Sun at slower average speeds, obeying the relationship p^2 = a^3.
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What did Galileo see through his telescope?
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Sunspots on the Sun, mountains and valleys on the Moon, four moons orbiting Jupiter, and the phases of Venus.
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What is the First Hallmark of Science?
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Modern science seeks explanations for observed phenomena that rely solely on natural causes. A scientific model cannot include supernatural elements.
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What is the Second Hallmark of Science?
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Science progresses through the creation and testing of models of nature that explain the observations as simply as possible.
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What is the Third Hallmark of Science?
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A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations.
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What must a scientific theory do?
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It must explain a wide variety of observations with a few simple principles, must be supported by a large, compelling body of evidence, and must not have failed any crucial tests of validity.
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A tentative explanation for an observation that can be tested by further investigation.
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hypothesis
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An observed mathematical relationship seen in nature, though we may not have an explanation for it.
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law
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An explanation that accounts for existing observations and predicts new ones.
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model
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A model that is supported by a large body of evidence and has not failed any tests of its predictions.
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theory
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The rate at which an object moves.
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speed
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What is the speed equation?
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speed = distance / time
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Speed and direction.
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velocity
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Any change in velocity.
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acceleration
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What is the momentum equation?
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momentum = mass x velocity
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Rotational momentum of a spinning or orbiting object.
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angular momentum
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The amount of matter in an object.
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mass
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The force that acts upon an object.
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weight
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What is Newton's First Law of Motion (Inertia)?
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An object moves at constant velocity unless a net force acts to change its speed or direction.
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What is Newton's Second Law of Motion?
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Force = mass x acceleration
F = m x a |
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What is Newton's Third Law of Motion?
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For every force, there is always an equal and opposite reaction force.
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What is the Universal Law of Gravitation?
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Every mass attracts other mass. Attraction is directly proportional to the product of their masses. Attraction is inversely proportional to the square of the distance between their centers.
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What is Newton's Law of Gravity?
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Gravity depends on masses of two objects divided by their distance, squared.
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What is Newton's version of Kepler's First Law?
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Orbits are ellipses, parabolas, and hyperbolas.
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What is Newton's version of Kepler's Second Law?
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An orbit's angular momentum is conserved.
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What is Newton's version of Kepler's Third Law?
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Orbital period depends on distance and the masses of the orbiting bodies.
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What is conservation of momentum?
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The total momentum of interacting objects cannot change unless an external force is acting on them. Interacting objects exchange momentum through equal and opposite forces.
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The collective kinetic energy of many particles. Depends on both temperature and density.
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thermal energy
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The average kinetic energy of the many particles in a substance.
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temperature
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How are tides caused?
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Tides are caused by the difference in gravitational pull across the Earth by the Moon.
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What is true of falling objects on a planet?
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Acceleration of gravity on a planet is the same for all falling objects, regardless of mass.
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