Earth Third Rock from the Sun

Earth- Is the 5 th largest planet. Is located third from the Sun. Is the largest rocky planet. Has one natural satellite, the Moon. Has seasons, due to the tilt of its axis and revolution. Is about 4.5 billion years old.

Earth is unique because- Water exists in all three states. Earth has oceans of liquid water and frozen ice caps. Earth has a protective atmosphere made of 78% nitrogen and 21% oxygen. It has an ozone layer which blocks the Sun’s ultraviolet radiation. It has a protective magnetic field. It is the only planet that supports life.

Water exists naturally in all three states.

75% of the Earth’s surface is covered by oceans..

Earth’s atmosphere

Atmospheric Gases

Ozone layer

Radiation Belts

Rotation An axis is an imaginary line around which a body spins. Rotation is the spinning of a planet or body on its axis. Rotation causes day and night. Earth and most other bodies in the solar system rotate counterclockwise. This causes the Sun to appear to rise in the east and set in the west. Earth’s rotation takes about 24 hours (23 hours and 56 minutes or one day).

Moon The Moon has no light of its own. It reflects sunlight. Round pits on the Moon are craters. Maria are dark flat areas that were once thought to be seas. The Moon is ¼ the diameter of Earth. The Moon has 1/6 the gravity of Earth. The Moon rotates on is axis and revolves or orbits Earth. Each takes 27.3 days to complete. Only one side of the Moon is visible from Earth.

Moon Phases The phases of the Moon are caused by its position relative to the earth and Sun. Phases take 29.5 days to complete.

Revolution Revolution is the movement of one body around another, such as Earth in its orbit around the Sun. Earth’s revolution takes about 365 days or one year (365 days, 6 hours, and 9 minutes). Earth’s orbit is an ellipse (an elongated, closed curve) with the Sun located a little towards one end. Earth is closest to the Sun in January.

Seasons Earth’s axis is tilted at 23.5 degrees from a line drawn perpendicular to its orbit. The tilt and revolution causes seasons. – The hemisphere tilted toward the Sun receives a greater number of daylight hours. – Sunlight strikes the hemisphere tilted toward the Sun at a higher angle, causing it to receive more solar radiation.

Seasons are reversed in the southern hemisphere. Northern Hemisphere

The solstice is the day the Sun’s direct rays reach the greatest distance north or south of the equator. These are the longest and shortest days of the year. Summer solstice is June 21 or 22. It is the first day of summer. Winter solstice is December 21 or 22. It is the first day of winter.

Winter Solstice

Eclipses Eclipses occur when the Earth or Moon temporarily block the sunlight from reaching the other. Eclipses may be total or partial. There are two types of eclipses, solar or lunar.

Solar Eclipses A solar eclipse occur when the Moon moves between the Earth and the Sun. The Moon casts its shadow over part of Earth. It is seen by only a few on the daylight side of Earth. It occurs only during a new moon. Solar eclipses are the rarest type of eclipse.

Lunar Eclipse A lunar eclipse occurs when the Earth’s shadow fall on the Moon. The Moon is in earth’s shadow. It is seen by everyone on the dark (night) side of Earth. Lunar eclipses only occur during a full moon.

Gravity Gravity is the force of attraction between objects. Gravity pulls objects toward each other. Gravity pulls the planets toward the Sun and moons toward their planet. Gravity acts everywhere in the universe.

The force of gravity pulls objects toward the center.

Gravity and Inertia Sir Isaac Newton explained that planets remain in orbit due to gravity and inertia. Gravity pulls objects toward each other. Inertia states that an object in motion will remain in motion and its movement will not change unless acted on by an outside force.

Gravity and Tides The rise and fall of sea level is a tide. It is caused by a giant wave produced by the gravitational pull of the Moon and Sun. As the Moon’s gravity pulls on Earth, it causes the Earth to bulge in two places, one on the side of the Earth facing the Moon and one on the opposite side of Earth.

On the side of Earth closest to the Moon, the surface of the water is pulled toward the Moon. On the opposite side, the land is pulled toward the Moon, allowing oceans to rise. This creates two high tides.

High tides occur at 90 degree angles to low tides.

Anywhere on Earth, there are two high tides and two low tides each 24 hours. However, because of Earth’s rotation, the tides are about 50 minutes later each day at any given location.

Spring and Neap Tides Spring tides occur when the Sun, Earth, and Moon are in a straight line. The tides are higher than usual. These tides only occur during full or new moons. Neap tides occur when the Sun is at a right angle to the Earth and Moon. The tides are lower than usual. These tides only occur on first and third quarter moons