2.2 and 2.4, Copernicus and Ptolemy

Heliocentric model

The sun is in the middle of the solar system, with the other planets revolving around it.

How did Galileo’s discovery of Jupiter’s moons prove Copernicus’ theory?

Jupiter had moons orbiting around it, meaning that not everything was centered around the Earth. Additionally, it proved that the Earth could move without the moon lagging behind it

How did Galileo’s discovery of Venus prove Copernicus’ theory?

Copernicus’ theory said that you can only see all of Venus’ phases if Venus revolves around the Sun. Galileo proved this through his telescope

How did Galileo's observation of the moon prove Copernicus’ theory?

Showed that Moon wasn’t perfect. It had canyons, valleys, etc, just like the Earth. Earth wasn’t special.

Why is the discovery of retrograde motion not significant?

Known since antiquity

Why does the discovery of stellar parallax matter?

This is because it was measured 2 centuries later in the 19th century

Retrograde motion

When planets appear to move backward/west because Earth is faster and it overtakes it, creating the appearance of leaving the planets behind.

Epicycle

Ptolemy’s idea that all the other planets revolved around the Earth in their own, individual orbits

Deferant

The orbit the other planets moved in around the Earth in Ptolemy’s model

Equant point

Imaginary point the planets can rotate around that explains varying speeds of the planets

What are characteristics of retrograde motion?

Brightening/dimming of an object, an object getting smaller/bigger, an object getting faster/slower