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Astronomy Concepts and History
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1
Question
What is the celestial sphere?
Page 1
Answer
An imaginary sphere surrounding Earth onto which all celestial objects (stars, planets, etc.) are projected.
2
Question
What is the purpose of the celestial sphere model?
Page 1
Answer
It helps astronomers visualize the positions and movements of celestial objects in the sky.
3
Question
Define the geocentric view in astronomy.
Page 1
Answer
A model where Earth is at the center of the universe, and all celestial bodies revolve around it.
4
Question
What is the zenith?
Page 1
Answer
The point directly overhead an observer.
5
Question
What is the nadir?
Page 1
Answer
The point directly below an observer, opposite the zenith.
6
Question
Define the horizon in celestial terms.
Page 1
Answer
The line where the sky appears to meet the Earth.
7
Question
What is latitude on the celestial sphere?
Page 1
Answer
The angular distance north or south of the Earth's equator.
8
Question
Describe the meridian.
Page 1
Answer
An imaginary line running from the north to south celestial pole, passing through the zenith.
9
Question
What are the north and south celestial poles?
Page 1
Answer
Extensions of Earth's rotational axis into space; the sky appears to rotate around these points.
10
Question
Define the circumpolar zone.
Page 1
Answer
The region around a celestial pole where stars never set.
11
Question
Why did ancient astronomers call planets 'wanderers'?
Page 1
Answer
They noticed some celestial objects moved differently from the fixed stars.
12
Question
What is the path of the Sun across the celestial sphere over a year?
Page 1
Answer
Epicyclic: the apparent orbit of the Sun.
13
Question
Define the zodiac.
Page 1
Answer
A band of the sky centered on the ecliptic, divided into 12 constellations.
14
Question
Through which sky band do planets, Sun, and Moon move?
Page 1
Answer
The zodiac.
15
Question
How many official constellations divide the sky?
Page 1
Answer
88 regions, each named after a mythological figure, animal, or object.
16
Question
What is Aristotle's round Earth argument from lunar eclipses?
Page 1
Answer
Earth's shadow on the Moon during a lunar eclipse is curved.
17
Question
How did Aristotle use star visibility to support a round Earth?
Page 1
Answer
As one travels north or south, different stars become visible or disappear.
18
Question
How did Eratosthenes measure Earth's circumference?
Page 1
Answer
By comparing the angle of the Sun's rays in Syene and Alexandria at the same time.
19
Question
What is precession of Earth's axis according to Hipparchus?
Page 1
Answer
The slow wobble of Earth's rotational axis, like a spinning top.
20
Question
How long does one cycle of Earth's axial precession take?
Page 1
Answer
About 26,000 years.
21
Question
What impacts does precession have?
Page 1
Answer
Affects positions of stars over long periods and changes the timing of seasons.
22
Question
What are epicycles in Ptolemy's model?
Page 1
Answer
Small circular paths planets were thought to follow while moving along larger circles (deferents) around Earth.
23
Question
How did Ptolemy explain complex planetary motions?
Page 1
Answer
Using epicycles and deferents.
24
Question
What is retrograde motion?
Page 2
Answer
The apparent backward movement of a planet across the sky compared to the stars.
25
Question
How did Ptolemy's model explain retrograde motion?
Page 2
Answer
Using epicycles.
26
Question
What was Copernicus's key idea (1473-1543 AD)?
Page 2
Answer
Heliocentric model: the Sun, not Earth, is at the center of the solar system.
27
Question
How does the heliocentric model naturally explain retrograde motion?
Page 2
Answer
Inner planets lap outer ones, appearing to loop backward.
28
Question
What was the significance of Copernicus's model?
Page 2
Answer
Marked a major shift from geocentric thinking and laid foundation for modern astronomy.
29
Question
Define Galileo's scientific method.
Page 2
Answer
A systematic approach to investigation involving observation, hypothesis, and experiment.
30
Question
What was Galileo's concept of motion?
Page 2
Answer
Rest is the natural state of matter, supporting possibility of moving Earth.