8-4.4

Days, Years, Moon Phases,

Eclipses and Tides

Day • A day is based on the 24 hours it takes

Earth to rotate.

• Earth rotates on its axis counterclockwise

from west to east; as a result, the Sun

appears to rise in the east and set in the

west.

Year

• A year is based on the 365.25 days it

takes Earth to revolve around the Sun.

• Earth revolves around the Sun in an

elliptical orbit.

Lunar Movement

• The Moon revolves with the Earth around the Sun as the Moon

is revolving around the Earth.

• The Moon revolves around Earth in 29.5 days.

• Similarly to Earth, as the Moon revolves, it is rotating or

spinning on its axis.

• The rotation time for the Moon is a little over 27 Earth days.

• Because the Moon rotates and revolves in nearly the same

amount of time, the same side of the Moon always faces Earth.

Phases of the Moon

• The Moon’s “phase” is the amount

of the lit side of the Moon we can

see.

• The phase depends on the relative

positions of the Sun, the Earth,

and of course, the Moon.

The Moon is Earth’s

Satellite

• Remember, just as Earth revolves

around the Sun, the Moon

revolves around the Earth. This is

important because it causes

shadows to be cast between the

Earth and Moon.

The New Moon

• The Moon is directly between the Sun

and the Earth.

• The Sun is lighting up the “dark side”

of the moon (the side we never see).

• The Moon is high in the sky, but can’t

be seen.

Waxing Phases

• As the Moon’s revolution continues, we start

to see a sliver that is illuminated by the Sun.

• The Waxing Phases are:

–Waxing Crescent (just a sliver)

–1st Quarter (half of the side that faces us is

lit)

–Waxing Gibbous (approaching full)

Tidbit: “gibbous” is Latin for “humpbacked”

The Full Moon

• The Full Moon only occurs when the

Moon is on the opposite side of Earth &

we can see the Sun fully illuminating it.

• P.S. We can only see ½ the Moon, so

could you call it a 2nd Quarter Moon

seeing how we have a 1st Quarter & 3rd

Quarter phase?

The Waning Phases

• After the Moon is full, the amount of what

we can see begins to recede (go away).

• The Waning Phases are:

–Waning Gibbous

–3rd Quarter (opposite than the 1st Q)

–Waning Crescent

…and then it starts all over again!

Eclipses

• An eclipse is a result of an alignment of Earth,

Sun, and Moon when either Earth or the Moon

temporarily blocks the Sun’s light from reaching

the other.

• Sometimes, during a New Moon, the Moon’s

shadow falls on Earth & causes a Solar Eclipse.

• Other times, during a Full Moon, the Earth’s

shadow falls on the Moon and causes a Lunar

Eclipse.

Lunar Eclipses

• Earth is directly between the Sun & the Moon.

• Lunar eclipses ONLY happen during a FULL MOON.

Solar Eclipses

• The Moon is directly between Sun and Earth.

• Solar Eclipses ONLY happen during a NEW MOON.

Tides • Tides are changes in the surface levels of

Earth’s ocean water. • Tides are caused by the effects of the Moon’s

and Sun’s gravitational pull on Earth.

Types of Tides •High Tides •Low Tides •Spring Tides •Neap Tides

High Tides •As moon orbits Earth, the waters of Earth closest to Moon bulge outward toward the Moon. Another bulge forms on the opposite side of Earth. These bulges are high tides.

High Tides

Low Tides •While most of Earth’s water is pulled toward the high tide bulges, the areas between high tides are called low tides.

Low Tides

Extreme Tides: Spring Tides • When Sun, Earth, and Moon are aligned in a straight

line, during New & Full phases, high tides are much higher than normal and low tides are much lower than normal. The tidal range is greater than normal.

•Straight=Spring

Spring Tides

Extreme Tides: Neap Tides • When Sun, Earth, and Moon are aligned at a 90 degree

angle, during 1st & 3rd Quarter phases, high tides are lower than normal and low tides are higher than normal. The tidal range is less than normal.

•Ninety=Neap

Neap Tides