Solar SystemEarth in Space

Motions of the Earth and Moon

• The shape of the moon appears to change and the lengths of daylight and darkness change throughout the year.

• These changes are caused by motions of Earth and its moon.

How do they move?

• Axis- imaginary line that passes through Earth’s North Pole to South Pole.

• Earth spins around on its’ axis. This is called rotation. A rotation takes about 24 hours or the length of one day. Earth’s rotation causes day and night.

How do they move?• In addition to rotating on

its axis, Earth travels around the sun. Revolution is the Earth moving around the sun, once each year. (365 days). This causes the lengths of day and night to change throughout the year.

• The path a moon or planet follows as it moves around the sun is it’s orbit.

• Seasons are caused by the Earth’s tilted axis and its revolution.

• There are four distinct seasons: winter, spring, summer, and autumn.

Seasonson

Earth

Summer does NOT occur because Earth is closest to the sun. Actually, Earth is closest to the sun in January and farthest away in

July.

Moon

• A moon is a natural satellite of a planet. A satellite is an object that stays in an orbit around a planet. The diameter is 3,476 kilometers, slightly more than one-quarter the diameter of Earth.

• The moon’s surface is thick with dust and dotted with rocks of various sizes. There is no water or air on the moon. The moon’s smaller size and lower mass gives it lower gravity causing your weight to be one-sixth of your weight here on Earth.

Moon Phases

• The moon is lit by sunlight bouncing off it, reaching the Earth as moonlight. The lit part we see depends on how much of the sunlit side of the moon faces Earth.

• Half of the moon is always lit by the sun! • The moon’s shape appears to change

called the moon’s phases.• The moon goes through eight phases as it

revolves around the Earth every 27.3 days. This equals about a month.

Phases of the Moon

1. New Moon

2. Waxing Crescent

3. First Quarter

4. Waxing Gibbous

5. Full Moon

6. Waning Gibbous

7. Third Quarter

8. Waning Crescent

Eclipses

• As the moon travels in its orbit, it sometimes moves between Earth and the sun, casting a shadow. An eclipse occurs when one object in space casts a shadow on another.

• A solar eclipse is when the moon casts a shadow on Earth. People on Earth who are in the moon’s shadow can’t see the sun for a few minutes.

During a Solar Eclipse

• The darkest part of the moon’s shadow, the umbra, is cone-shaped.

• The largest part of the shadow, the penumbra, allows part of the sun to be visible from Earth.

TIDES

• Tides are changes in ocean water levels that take place in a regular pattern. These are controlled by the pull of gravity between the moon and Earth.

• The force of gravity due to the moon pulls ocean water away from Earth’s surface. As Earth rotates, water is pulled up onto the shore causing high tides. When water is pulled away from the shoreline it is called low tides.

• Twice a month during new moon and full moon, spring tides occur when the gravity of the sun and the moon pull in the same direction. The combined forces produce a spring tide with the greatest difference between low and high tide.

Also, twice a month during the moon’s first quarter and last quarter moon phases, a neap tide occurs. This occurs when the moon is at a right angle producing a neap tide with the least difference between high and low tide.