Motions of the earth

MOTIONS of the EARTH

•  REVOLUTION

The movement of the earth in its orbit.

•  ROTATION

The spinning of an object on its axis.

•

Precession –

The spin axis of the Earth undergoes a motion

•

This changing of direction of the spin axis is called

precession.

Seasons of the Earth

Earth at Winter Solstice

Earth at Summer Solstice

Why do we have seasons?

The Winter & Summer Sun

Seasons in the Northern &

Southern Hemisphere

Solstices

•

The solstices are days when

the Sun reaches its farthest

northern and southern

declinations.

•

The winter solstice

occurs on

December 21 or 22 and marks

the beginning of winter (this is

the shortest day of the year).

•

The summer solstice

occurs

on June 21 and marks the

beginning of summer (this is

the longest day of the year).

Equinoxes

•

Equinoxes are days in which day

and night are of equal duration.

The two yearly equinoxes occur

when the Sun crosses the

celestial equator.

•

The vernal equinox

occurs in late

March (this is the beginning of

spring in the Northern

Hemisphere and the beginning of

fall in the Southern Hemisphere);

the autumnal equinox

occurs in

late September (this is the

beginning of fall in the Northern

Hemisphere and the beginning of

spring in the Southern

Hemisphere).

Summary