Our Corner of the Universe

1. Our Corner of the Universe 100 mil ly 5 mil ly

2. Our Neighborhood

3. Earth’s rotation, orbit and the seasons • Only 50% of the Earth’s surface can be “lit” by the sun • Because the Earth’s axis is tilted the area covered by this 50% varies throughout the year

4. Most important variables • Earth’s orbit is 365.25 days long • Earth’s axis of rotation tilts 23.5° from the perpendicular • These two variables account for the seasonal changes in weather patterns that we observe in a given year

5. We have four seasons: why? The Earth’s axis of rotation is tilted at 23.5° from the perpendicular

7. Earth-Sun Relations

8. Latitude • Affects the amount of insolation received at the Earth’s surface • The subsolar point(at right angles to the plane of the ecliptic) receives most insolation • Insolation decreases north and south of this point • The subsolar point migrates from 23.5°N in the summer to 23.5°S in the winter

9. Subsolar point

10. The latitudinal zones

11. Perihelion vs Aphelion

12. MILANKOVITCH CYCLES • ACCOUNTS FOR PERIODIC GLACIATION OF EARTH

13. MILANKOVITCH CYCLES

14. MILANKOVITCH CYCLES

16. THE NEXT ICE AGE? WHEN