September 19, 2013.
Lecture 4 –The Night Sky, Constellations, and Seasons
Why do we have seasons?
The orbit is almost circular, it’s not about distance between the Earth and Sun
It’s about the amount of energy reaching/touching the Earth’s surface
o Per unit area
Earth is tilted by 23.5 degrees, seasons are determined by which hemisphere is tilted
towards/away from the sun
Do other planets have seasons?
o Jupiter’s tilt is 5 degrees, no seasons
The plane where the Earth moves around the Sun is called Ecliptic
Trying to make sense of it….
We invent the term “celestial sphere” to define the dome of stars surrounding Earth,