Earth's Revolution Around the Sun
Earth is constantly moving in 2 different ways that we will discuss over the next two lessons. We are constantly revolving around the Sun, and at the same time we are constantly rotating around our axis. It is important for us to understand the difference between these two motions, as well as the effects that each motion has on us. This lesson will focus on the first of those two motions...REVOLUTION.
Revolution is the movement of one object around another object.
Earth revolves around the Sun in an elliptical orbit, just as the Moon revolves around the Earth in an elliptical orbit.
WE REVOLVE AROUND THE SUN IN A COUNTER-CLOCKWISE DIRECTION
THE RATE OF REVOLUTION IS ABOUT 1 DEGREE PER DAY
How do we Know we're Revolving?
Evidence #1: Changing Seasons
Because our axis is tilted, as we revolve around the Sun, the angle of insolation changes throughout the year.
For part of the year the Northern Hemisphere is tilted towards the Sun.
- This means the Northern Hemisphere gets more direct sunlight at a HIGHER ANGLE OF INSOLATION
- This means HIGHER TEMPERATURES
For part of the year the Northern Hemisphere is tilted away from the Sun.
- This means the Northern Hemisphere gets less direct sunlight at a LOWER ANGLE OF INSOLATION
- This means LOWER TEMPERATURES
SPRING / FALL
In the spring and fall the Earth is not tilted towards the sun or away from the Sun.
- This means the Northern Hemisphere gets MEDIUM ANGLES OF INSOLATION
- This means MEDIUM TEMPERATURES
Evidence #2: Changing Constellations
Everyday the part of the Earth facing the Sun experiences daylight, and the half of the Earth not facing the Sun experiences night. The night time part of Earth faces out into space so we see stars!
Constellations are groups or clusters of stars that together form an image in the night sky. Constellations are named after Greek myths.
The constellations that we see at night depend on the part of space we are facing. As we revolve around the Sun, the night time part of Earth is facing different parts of space, so we see different constellations at different times of year!
This is why your zodiac sign is dependent upon your birthday. The zodiac symbols are all constellations, and your sign is based on the constellations present during the month of your birth.