Space CyclesReview

Cycle # 1

Day Night Day Night

We have day and night because the Earth ROTATES

• On it’s axis• Once every 24

¼ hours• ½ of the Earth

is illuminated (lit up) at a time

http://www.gcse.com/eb/day2.gif

Cycle #2The length of days

Long Longer Longest Longer Long Short Shorter Shortest Short Shorter Shortest Long Longer

Longest

The length of day changes during the year

• The number of hours of daylight is different at different times of the year

• The number of hours of daylight is different at different latitudes

Summary

• Days are longer (more hours of daylight) in summer, shorter in winter

• There are greater differences in day length further away from the Equator

• There is not much change in day length near the Equator

Summary

• Days get LONGER (more minutes of daylight each day) from the Winter Solstice to the Summer Solstice

• Days get SHORTER (fewer minutes of daylight each day) from the Summer Solstice to the Winter Solstice

• Day length is about EQUAL everywhere in the world on the Autumnal & Vernal Equinox

Why does the length of day change?

• Because the Earth moves, or REVOLVES around the Sun

• This changes the way sunlight hits the Earth

Cycle # 3The Seasons

Winter Spring Summer Fall Winter Spring Summer

http://www.getyourwebsitehere.com

Seasons are caused by

• The tilt of the Earth

• The position of Earth in space

• The difference in direct and indirect light from the Sun

Summary

• In winter:– Part of the Earth

is tilted AWAY from the Sun

– Part of the Earth gets INDIRECT energy from the Sun

• In summer– Part of the Earth

is tilted TOWARD the Sun

– Part of the Earth gets DIRECT energy from the Sun

The position of the Earth in space determines which part of the planet is tilted toward the Sun.

Cycle # 4Moon Phases

New moon Waxing Crescent 1st Quarter Waxing Gibbous Full

Moon Waning Gibbous 3rd Quarter Waning Crescent New Moon

The Moon

• A moon phase cycle (LUNAR CYCLE) lasts 29 1/2 days

• Moon phases are caused by the positions of the Moon, Sun, and Earth

• The moon also sees Earth phases

http://www.astro.virginia.edu

What we see on Earth

compared to the position of the moon in

space

DAY 1 The Moon's unilluminated (not lit by the Sun)

side is facing the Earth. The Moon is not visible.

New Moon

DAY 3The Moon seems to be getting bigger –

more of the lit side is showing.

WAXING CRESCENT

Getting bigger:

WAXING

The RIGHT ½ of the

moon is lit

Less than ½ the moon showing:

CRESCENT

FIRST QUARTER

DAY 7One-half of the Moon is illuminated by

direct sunlight.

One half of one half of the moon is

visible.

Waxing Gibbous

DAY 11The Moon is more than one-half but not fully

illuminated by direct sunlight.

GIBBOUS: more than half of the moon is visible.

Full Moon

DAY 14The Moon's illuminated side is facing the Earth.

The Moon is completelyilluminated by direct sunlight.

Waning Gibbous

DAY 17The Moon is more than one-half but not fully

illuminated by direct sunlight.

Waning: getting smaller.

Moon is lit on the LEFT

side

Last Quarter

DAY 22One-half of the Moon is illuminated

by direct sunlight.

Waning Crescent

DAY 24The Moon is less than one-half illuminated by direct sunlight.

http://www.facstaff.bucknell.edu

Summary