Our Corner of the Universe 100 mil ly5 mil ly

Our Neighborhood

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

Most important variables  Earth’s orbit is 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 These two variables account for the seasonal changes in weather patterns that we observe in a given year

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

Earth-Sun Relations

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 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

Subsolar point

The latitudinal zones

Perihelion vs Aphelion

MILANKOVITCH CYCLES - ACCOUNTS FOR PERIODIC GLACIATION OF EARTH

MILANKOVITCH CYCLES

THE NEXT ICE AGE? WHEN