Our Planet Earth Seasons, Moon Phases and Ocean Tides The Earth, Moon and Sun System

GRAVITY The force that keeps the Earth revolving around the Sun and the moon revolving around the Earth

Rotation vs. Revolution Rotation –Spinning on its axis –Takes Earth 24 hour to rotate 1 time –Causes day and night Revolution –Orbiting around another object –Take Earth 365 days (1 year) to revolve around the Sun –Causes Seasons

Earth’s Seasons Caused by the tilt of the Earth on it’s axis. Caused by the revolution of the Earth around the sun.

Seasons

Earth’s Tilt on its Axis

Day Length Summer – longest days –June 21 st : Summer Solstice – longest day of the year. Winter – shortest days –Dec. 21 st : Winter Solstice – Shortest day of the year Spring and fall – Equal days and nights. –March 21 st : Spring Equinox –September 21st: Fall Equinox

Night and Day Caused by the ROTATION of the Earth on it’s axis.

The Lunar Cycle The moons orbit (revolution) around the Earth Takes about 28 days (one month) Causes the phases of the moon that we see from Earth

Phases of the Moon Half of the moon is always illuminated by the sun From Earth, we see different phases of the moon as it revolves around the Earth. SUN

Phases of the Moon as it revolves around the Earth

Lunar Cycle – Lasts about 28 Days (1 month)

Predicting the Phases of the Moon

Waxing vs. Waning Waxing - sun lit part of the moon seen from Earth is getting bigger –We see the right side of the moon Waning – sun lit part of the moon seen from Earth is getting smaller –We see the left side of the moon

Waxing vs. Waning Lunar Phases

The Lunar Cycle Takes about 7 days to reach each quarter New moon - 1 st quarter – Full moon – 3 rd quarter 28 days total

Ocean Tides Daily changes in the level of ocean water. Caused by the gravitational pull of the moon. Tides are effected by the position of the Moon and the Sun.

High Tides vs. Low Tides High Tide - Ocean water bulges out on opposite sides of the Earth due to the gravitational pull of the Moon. Low Tide – Ocean water is drawn away from the area between the high tides. High and Low tides occur every six hours –Two times each every 24 hours.

Tidal Ranges The difference between levels of ocean water at high tide and low tide. –Spring tides - tides with the largest daily tidal range (largest difference). –Neap tides - tides with the smallest daily tidal range (least difference).

Spring Tides Large Tidal Ranges Highest high tides and lowest low tides Occurs during Full and New Moon Phases The Sun, Earth and Moon are in a straight line (very strong gravitational pull)

Neap Tides Low Tidal Ranges Not much difference in high and low tides Occurs during 1st and 3rd Quarter Moon Phases The Sun, Earth and Moon are at a right angle (Weak gravitational pull)