Early Models of the Solar System

Question 1

Describe the observation of solar and lunar cycles by ancient civilisations for agriculture?

Answer 1

Understanding of seasons and the day’s varying length was required for farming. E.g. Egyptians used the time of Sirius’ rise after sunset to predict the flooding of the Nile

Question 2

Describe the observation by ancient civilisations around the world for religious systems

Answer 2

Ancient civilisations built stone monuments or religious temples aligned to the stars or the sun.e.g. Stonehenge

Question 3

Describe how the current celestial alignment relates to the original alignment

Answer 3

They are different due to the precession of Earths axis over 26,000 years. This is useful to date these ancient monuments in archeoastronomy.

Question 4

Describe the early geocentric solar system models, and the addition of epicycles by Ptolemy

Answer 4

These involved an Earth - Centred model orbited by planets and the sun. Ptolemy theorised epicycles and an off-centre Earth to better fit the observed motion of the planets

Question 5

Describe the timeline of the heliocentric model

Answer 5

1. Copernicus was the first to theorise a heliocentric universe, but did not publish it until death due to fear of conflicting the church
2. Tycho Brahe plotted the position of Mars over 20 years, allowing his apprentice Johannes Kepler to formulate his three laws of planetary motion in 1609
3. Galileo Galilei used his telescope to observe the skies, using the 4 moons orbiting Jupiter and the changing of Venus’ apparent size to prove the heliocentric model

Question 6

What are epicycles and how do they actually work

Answer 6

They involve the planet orbiting a centre of mass, that is orbiting the Earth. Like the moons orbit around the sun, where Earth is the centre. They explain retrograde motion as they occasionally move backwards in the sky