Welcome Astronomers to the Sun, Moon, and Earth!  The relationship

between the Sun, Moon, and Earth is very important to the existence of life on Earth. Our

quest is to find out how their relationships affect day and night, years, the seasons around the

world, and the phases of the moon.

Day, Night, Year, and Seasons

Purpose/Objective:  The students will be able to:1)Describe how the Earth’s rotation on its axis relative to the Sun causes the Earth to experience cycles of day and night.2) Describe how Earth’s 365-day revolution around the Sun allows us to have years.3) Explain the reason why Earth passes through four different seasons during its revolution around the Sun.4) Relate the Moon phases to changes in the Moon’s position relative to the Earth and Sun during its 29-day revolution around the Earth. 

Rotation – Earth spinning on axis.

1 rotation = 24 hours

Part of Earth facing sun = day

Part of Earth facing away from Sun = night

RotationWhat does Rotation mean?Rotation occurs when something is spinning around an axis.

What are some examples of things that rotate?Tops, Ballerinas, Figure skaters, cyclones, Tornadoes, a merry-go-round,

Earth

How do we know that the Earth rotates?1. Star trails- trails made with time exposure, circular paths that occur

because the planet is moving and not stationary.2. Winds curve because of the Earth’s rotation.3. Ocean currents curve clockwise in the northern hemisphere, and

counterclockwise in the southern hemisphere.4. The movement of a pendulum. It does not actually move, it is the

Earth moving that causes the pendulum to appear to change the direction of its swing.

Night and DayWhat causes night and day?The rotation of the Earth• The side of the Earth that is facing the sun has daylight, the side of

the Earth away from the sun has night.• It takes 24 hours for the Earth to complete one rotation.• The Earth is tilted on it’s axis at a 23.5 degree angle.• The Earth’s tilt is always in the direction of the North Star.What is another name for the North Star?Polaris• This tilt is what causes our days to get longer in the summer and

shorter in the winter.• Because of the Earth’s rotation the sun appears to rise in the east

and set in the west.

Revolution – movement of 1 object around another object.

Earth Revolution around Sun = 1 year (365 days)

One revolution around the sun equals 365 days. This

revolution causes the changing of the seasons.

Orbit – the path an object takes as it revolves around another

object.

Axis – Imaginary line passing through Earth causing it to rotate. Earth tilted

23.5 degrees on axis.

SeasonsWhat two things cause the difference in the seasons?1. The angle of the sun’s rays2. The length of the days

There are two kinds of rays from the Sun:1. Direct- occurs when Earth is tilted toward the Sun2. Indirect-occurs when Earth is tilted away from the SunIn the Summer, we get the direct rays from the sun

and the days are longer. (But we are farther away from the Sun)

In the Winter, we get indirect rays from the Sun and the days are shorter. (But we are closer to the Sun)

Why does this happen?

Seasons are caused by the tilt of the Earth

Direct Sunlight• more direct at the equator• more indirect at the poles

Not to scale, the Sun is MUCH bigger than the Earth.

Winter in Northern Hemisphere = Summer in Southern Hemisphere.

Winter Solstice 1st Day of Winter, Dec. 22. Longest Night

Summer in Northern Hemisphere = Winter in Southern Hemisphere.

Summer Solstice 1st Day of Summer, June 21.Longest Day

Spring in Northern Hemisphere = Fall in Southern Hemisphere.

Vernal Equinox 1st day of Spring, March 21. Equal Day and Equal Night

Fall in Northern Hemisphere = Spring in the Southern Hemisphere.

Autumnal Equinox 1st day of fall Sept. 23Equal Day and Equal Night

The Four Seasons: The Effect of the Tilt of Earth’s Rotation Axis

The Phase of the Moon

The phase of the Moon depends on the relative position between the Sun, the Earth, and the Moon…

>> 0 >> 1 >> 2 >> 3 >> 4 >>

The light from the sun is hitting the side

of the moon facing away from the Earth.

Those are the same stars, and that is the same moon, that look down upon your

brothers and sisters …”Sojourner

Truth

In the diagram above, you can see the Moon always has a lit side (facing the Sun) and a dark side (facing away from the Sun). From the Earth, we can only see the part of the Moon that is facing toward us at any time (which is often called the near side of the Moon) and we cannot see the part of the Moon facing away from Earth ( called the far side of the Moon). The phase of the Moon, or the shape of the lit part of it, that we see at any time is then determined by the combination of these two factors - which part of the Moon is lit by the Sun and visible to Earth at the same time!

(Requires Java).

To summarize, the phases of the Moon are caused by the

Sun only lighting up half of the Moon and our angle of seeing

the Moon. The phases of the Moon are

not caused by the Earth's shadow.

Finished • Go to New path learning

• Earth, Sun & Moon– Don’t have a code? Come see me or can’t

remember? Come see me– Go to USA TEST PREP

• What Causes Seasons? (01:35)• S6E2.c.) Earth tilt and solar energy

(S6E2.a.) Earth, Moon, and Sun