Chapters 2 and 3 Flashcards
From where on Earth could you observe all of the stars during the course of a year?
Equator line
What fraction of the sky can be seen from the North Pole?
Half of the sky
Explain, according to both geocentric and heliocentric cosmologies, why we see retrograde motion of the planets.
The geocentric model explains this with the epicycle
The heliocentric model explains this as the earth goes faster then around the sun then other planets
Both making the planets look like they are going opposite directions (retrograde motion).
What were four of Galileo’s discoveries that were important to astronomy?
- Venus phases
- 4 moons around Jupiter
- More stars then the human can see
- Craters and mountains on the moon
Ursa Minor contains the pole star, Polaris, and the asterism known as the Little Dipper. From most locations in the Northern Hemisphere, all of the stars in Ursa Minor are circumpolar. Does that mean these stars are also above the horizon during the day? Explain.
Yes, the stars are circumpolar (visible above the horizon at all times at a specified locality on the earth’s surface), but you can’t see them during the day due to sunlight/ moonlight.
How many degrees does the Sun move per day relative to the fixed stars?
The sun moves 1 degree a day
How many days does it take for the Sun to return to its original location relative to the fixed stars?
The sun takes 365 days
Is the ecliptic the same thing as the celestial equator? Explain.
Ecliptic: Annual path of the sun
Celestial equator: The 0 degree equator on earth lined outside
The earth is tilted 23.5 degrees, so they never align
What is an asterism? Can you name an example?
An asterism is a group of stars that are recognizable, an example are the big and little dipper
What two factors made it difficult, at first, for astronomers to choose between the Copernican heliocentric model and the Ptolemaic geocentric model?
One of the objections was if Earth were moving, we would all sense or feel this motion. Another objection was religious related, stating that God would make the us center of universe
What is a constellation as astronomers define it today? What does it mean when an astronomer says, “I saw a comet in Orion last night”?
A constellation is a well-defined area of the sky with borders, the astronomer is talking about a region in the sky with said constellation.
What were two arguments or lines of evidence in support of the geocentric model?
No parallax or wind, meaning earth is stationary and in the center.
Although the Copernican system was largely correct to place the Sun at the center of all planetary motion, the model still gave inaccurate predictions for planetary positions. Explain the flaw in the Copernican model that hindered its accuracy.
The model had the planetary orbits in perfect circles and the same speed for each planets orbit.
Why did Kepler need Tycho Brahe’s data to formulate his laws?
Tycho had more accurate measurements of the geocentric cycle.
- Which has more mass: an armful of feathers or an armful of lead?
- Which has more volume: a kilogram of feathers or a kilogram of lead?
- Which has higher density: a kilogram of feathers or a kilogram of lead?
- Lead
- Feathers
- Lead
