A7 - Early models of the Solar System

Question 1

What were detailed observations of lunar/solar cycles used for by ancient civilisations?

Answer 1

-agricultural systems
-religious systems and festivals
-time/calendar systems
-alignments of ancient monuments

Question 2

Why did ancient civilisations use detailed observations of the solar/lunar cycles for agricultural systems?

Answer 2

to know when the best time it is to plant/harvest crops

Question 3

Why is the current celestial alignment of ancient monuments not exactly correct?

Answer 3

axial precession (NCP moves and so the apparent motion of the stars change over time)

Question 4

Describe an example of a very early geocentric model of the Solar System, and give 1 observation that made it inaccurate:

apart from the fact that it was geocentric

Answer 4

-Aristotelian Universe

-4 elements (earth, air, fire, water)
-a system of concentric crystalline spheres driven by a “prime mover” that carried the Moon/Sun/other planets/stars

-it couldn’t explain the retrograde motion of planets

Question 5

How was the problem of geocentric Solar System models not explaining retrograde motion fixed?

Answer 5

-Ptolemy added in epicycles

-planets had a circular path around the Earth (remember its geocentric), but also followed an additional circular path that would follow along with the initial circular path, known as an epicycle

Question 6

What is a parsec?

Answer 6

the distance that an object has to be for it to have a heliocentric parallax angle of 1 arcsecond

~3.26 light years