Unit 2 Introduction Flashcards
What is the nebular hypothesis?
The nebular hypothesis describes the formation of star-planet systems, including our Solar System, from a cloud of gas and dust that collapses under gravity.
What does the geocentric model state?
The geocentric model places Earth at the center of the Solar System, with other celestial bodies orbiting around it.
What does the heliocentric model state?
The heliocentric model places the Sun at the center of the Solar System, with planets, including Earth, orbiting around it.
Describe Pythagorus/Plato’s models of the solar system
- one of the earliest models - around 530 BC
- Pythagoras developed one of the earliest models, placing Earth at the center as a stationary object, surrounded by a sphere rotating celestial objects, including the Sun
- Plato tried his hand at a model but nothing was any better than Pythagorous’s model
What was Aristarchus’ contribution to astronomy?
Aristarchus (310-230BC) proposed a heliocentric model with the Sun at the center of the Solar System, though he did not promote his model.
What was Ptolemy’s model of the Solar System?
Ptolemy’s (85-170 AD) model, which lasted 1,400 years, placed Earth at the center with celestial objects on moving spheres, supported by the Catholic Church.
What was Copernicus’ major contribution to the Solar System model?
Copernicus (Middle Europe around 1514) proposed a heliocentric model where Earth rotates around the Sun and on its own axis, challenging the geocentric model.
* model did a great job of predicting observations
* the church would not allow him to publish his model
* his friends published a model of his work with the preface that it should not be taken as representing reality, to protect them from the Church
What did Tycho Brahe observe in 1572 that challenged existing models of the cosmos?
Tycho Brahe (1572) observed a supernova, which he concluded was much further away than any object in previous cosmos models.
* generated fame by discussing this star and what it meant
* promted the King of Denmark to give him a grant with which he built world’s first observatory
* the precise records of star and planet positions that Tycho assumed as still used by astronomers
What system did Tycho Brahe propose?
Tycho proposed a model where the Sun moves around the Earth, but other planets orbit the sun, blending elements of the geocentric and heliocentric models.
What were Johannes Kepler’s contributions to astronomy?
Kepler (1571-1630) developed three laws of planetary motion and proposed that planets orbit the Sun in elliptical paths, influenced by a force he believed to be magnetic.
What was Kepler’s first law of planetary Motion?
defines the construction of an ellipse because he realized planets did not move in perfect circular paths
The Sun as one focal point, the other a hypothetical point in space. The sum of the distances of any point on the ellipse from the two foci is a constant, meaning the Earth-Sun distance is constantly changing as the planet goes around orbit.
Define the 2 terms introduced by Kepler:
Perihelion
Aphelion
Perihelion: The point of a planet’s orbit that is closest to the sun
Aphelion: The point of Greatest separation
