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20 Cards in this Set
- Front
- Back
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Winter solstice falls on the _____ day of the year |
Shortest |
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Summer solstice falls on the ______ day of the year |
Longest |
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Aristarchus (310 - 230 BC) |
First to propose heliocentric solar system |
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Erastosthenes (276 -195 BC) |
Measured Earth's circumference using 2 sticks and a slave assistant. |
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When era sparked an intellectual revolution after the fall of science in the dark ages? |
The Renaissance (14/15th century) |
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Ptolomy (90-168 AD) |
Introduced the geocentric universe where Earth is at the center (wrong) but Mercury, Venus, & Mars are correctly placed. This model worked so well that it took 1400 yrs to debunk. |
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What is wrong with the geocentric model? |
It cannot account for retrograde motion |
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Retrograde |
The apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point.
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Retrograde of Mars |
Earth "laps" Mars on its way around the Sun, so it looks like we get closer and then further away again. Mars appears to slow down, move backward, and then forward again (relative to other stars) |
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Which astronomers first challenged the geocentric universe model? |
Copernicus, Tycho, Kepler, and Galileo |
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Copernicus (1473-1543) |
Re-proposed the heliocentric universe & built model to determine layout of the solar system - Sadly, model was not more accurate bc he still thought that the planets moved in perfect circles. - Created the AU |
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Tycho Brahe (1546-1601) |
Compiled the best naked-eye measurements of the planetary positions. - Hired Kepler, who used Tycho’sobservations to discover the truth about planetary motion. |
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Johannes Kepler (1571-1630)
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First tried to match Tycho’sobservations with circular orbits
...but an 8-arcminute discrepancy led him to make a model of planet orbits using ellipses |
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Ellipse |
An elongated circle or oval |
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Kepler’s Law of Planetary Motion #1 |
The orbit of each planet around the Sun is an ellipse with the Sun at one focus.
The planet switches from being at perihelion & aphelion depending on its place in orbit. |
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Perihelion/Aphelion |
Perihelion: Planet is in close proximity to sun in its ellipse. Aphelion: Planet is farther away from sun in its ellipse. |
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Kepler’s Law of Planetary Motion #2
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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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Kepler’s Law of Planetary Motion #3
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More distant planets orbit the Sun at slower average speeds, obeying the relationship:
p^2 = a^3 p = orbital period in years a = avg. distance from Sun in AU |
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Galileo Galilei (1564-1642)
"father of modern observational astronomy” |
Improved the telescope and consequent astronomical observations.
Supported Copernicanism (heliocentricity) Discovered 4 largest satellites of Jupiter (now called the Galilean Moons). |
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How did Galileo solidify the Copernican revolution?
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1. Earth could not be moving because objects in air would be left behind.
2. Non-circular orbits are not “perfect” 3. If Earth were really orbiting Sun, we’d detect stellar parallax, our view of nearby stars would change as we moved around. |
