Quadrature Actual Moon Opposition Conjunction Earth Sun's Rays

View from earth
first quarter

View from View from
earth waxing earth waxing
gibbous crescent

Quadrature Actual Moon

View from Opposition Conjunction View from
earth full earth New
moon moon

Earth

Quadrature

View from View from Sun's Rays
earth waning earth waning
gibbous crescent

View from earth
third quarter

Lunar Phases and Configurations

As the Moon orbits the Earth, we see varying portions of its sunlit side. The phases sketched
here (outside the circle representing the Moon's orbit) show the Moon as it appears to an
observer in the northern hemisphere.

Figure by MIT OCW.

Sun

Earth Moon

Solar Eclipse

Umbra

Moon Earth Sun
Penumbra Lunar Eclipse

Solar and Lunar Eclipses

The relative positions of the Sun, Earth, and Moon are shown at the times of solar (upper) and
lunar (lower) eclipses. Only the dark portion of the shadow (the umbra) is shown in each case.
(Not to scale)

Figure by MIT OCW.

Sun

Ecliptic Plane

Northern Summer Northern Winter
Southern Winter Southern Summer

Seasons
The Earth's tilted axis retains its orientation as the Earth orbits the Sun. Thus, at opposite
points in the orbit, each hemisphere has winter and summer, depending on whether that
hemisphere is tipped towards the Sun or away from it.

Figure by MIT OCW.

Sun's Rays N Arctic Circle
23.5o Tropic of Cancer
Equator
Tropic of Capricorn

Antarctic Circle

S

The Earth on June 22, the summer solstice in the Northern Hemisphere.

Figure by MIT OCW.