1. Motion across the Sky

2. Learning goals
We are learning how celestial objects move in our night sky.
We are learning to distinguish between different types of satellites.

3. Ecliptic
Ecliptic: the path across the sky that the Sun, the Moon, the planets, and the Zodiac constellations appear to follow over the course of a year

4. Changing Views in the Night Sky
changing views in the night sky are due to:
Earth’s rotation
distance celestial object is from Earth
Earth’s revolution around the Sun

5. Retrograde Motion
retrograde motion: the apparent motion of an object in the sky from east to west, rather than west to east
occurs because Earth travels around the Sun faster than the outer planets

7. satellites

8. history 1957 USSR: Sputnik 1 – size of football
Sputnik 2 – much larger
1958 USA: Explorer 1
Alouette 1: Canada !
Anik 1 in 1972: transimitted 12 tv channels

9. orbit Earth’s gravity pulls – satellite must have enough velocity
Low earth orbit – up to 2000 kms
military and earth observation
International Space Station (430km above earth) travels at a speed of km/h

10. Geostationary orbit
Satellite which orbits Earth at same rate as Earth rotates km
used to broadcast tv, radio and internet

11. gps Global Positioning System medium earth orbit (up to 35000km)
uses three satellites to triangulate position

12. Learning goals
We are learning how celestial objects move in our night sky.
We are learning to distinguish between different types of satellites.

13. Homework:
Section 8.9 #1, 3-7
Section 8.11 #7