Exam 1 Flashcards
What did Erasthenes do?
Estimate the size of the Earth using the approximation that since the Sun is very far, its rays are almost parallel.
What did Aristotle prove about the Earth?
Aristotle determined the Earth was round because of Earth’s shadow on the Moon and because of the rotation of the celestial sphere as you travel on the planet.
What did Aristotle observe about the Moon?
That its light was caused by the light of the Sun reflecting on its surface.
What is the difference between a waxing and a waning Moon?
A waxing Moon’s illuminated part is growing bigger, and the opposite for a waning Moon.
What is the range of angle of elongation of a waning gibbous Moon?
Between 90 and 180 degrees.
What important discovery did Aristarchus make?
He estimated the distance between the Earth and the Moon in terms of distances between Earth and Sun.
Who is Hipparchus? What were some of his important discoveries?
Hipparchus was the greatest astronomer of antiquity. He calculated the length of a year with a 6 minute accuracy, he catalogued 850 stars, which he classified according to brightness. His system of classification is at the basis for our modern system. He also discovered the procession of the Earth (rotation of the axis of rotation).
Why did Aristotle adopt a geocentric model?
He observed no stellar parallax, which he wrongly concluded was due to the fact everything revolved around the Earth.
What does “planet” mean in Greek?
Wanderer
What contributions did Ptolemy bring to astronomy?
He created a geocentric model that accounted for the retrograde motion of planets (epicycles).
What did Copernicus contribute?
He adopted a Heliocentric model.
How could Ptolemy’s model be broken?
According to Ptolemy’s model, we would only be able to observe Venus in its new or crescent phase. If we could observe Venus in any of its other phases, the Heliocentric models would be proven true.
Who was Tycho Brahe?
He was the last great naked eye Astronomer. He measured the positions of planets within 1 arcminute of accuracy. He hired Kepler to help create a model.
Who is Johannes Kepler? What were his three laws of planetary motion?
Mathematician who proved planetary orbits were ellipses.
Laws:
1) All planet follow elliptical orbits with the Sun as a focal point.
2) Planets get faster as they get closer to the Sun. (Area swept by the imaginary line is constant).
3) The square of the planet’s period of revolution is proportional to the cube of its semi-major axis.
What were Galileo’s 5 most important observations? What were their significance?
1) Moons of Jupiter: Not everything revolves around the Earth.
2) All the phases of Venus are visible (Geocentric = dead af)
3) Surface of the Moon is imperfect: Celestial bodies are not perfect beings.
4) Sunspots: Sun is not perfect
5) Milky way: The telescope can reveal something hidden to the human eye.
