Pick a science word and write the definition. Bell work Week 27 Pick a science word and write the definition. Chapter 20

Title of notes: The Earth-Sun System Pg.19, 20, & 21 RS Goal for lesson: write on your self assessment worksheet I can define rotation and revolution and how it relates to Earth

The Earth-Moon-Sun System People have always been fascinated by the changing positions of the sun and moon in the sky Prehistoric people, for example, built observatories The structure known as Stonehenge was probably an attempt to better solar predictions

The Earth-Sun System At the beginning of summer in the Northern Hemisphere (the summer solstice on June 21 or 22), the rising sun comes up directly above the heel stone of Stonehenge Besides keeping this calendar, Stonehenge may also have provided a method of determining eclipses

Earth Earth is the third planet from the sun. Only planet with free oxygen, oceans of water on the surface, and life. Formed roughly the same time as the sun about 4.6 billion years ago.

Roughly 78 percent nitrogen and 21 percent oxygen Earth’s Atmosphere Roughly 78 percent nitrogen and 21 percent oxygen Air surrounds Earth and gets thinner as you get farther from the surface The upper atmosphere expands during the day and contracts at night due to heating and cooling

Motions of Earth The two main motions of Earth are rotation and revolution Rotation is the turning, or spinning, of a body on its axis Revolution is the motion of a body, such as a planet or moon, along a path around some point in space

Motions of Earth For example, Earth revolves around the sun, and the moon revolves around Earth Earth also has another very slow motion known as precession, which is the slight movement, over a period of 26,000 years, of Earth’s axis

Rotation The main results of Earth’s rotation are day and night Earth’s rotation has become a standard method of measuring time because it is so dependable and easy to use Each rotation equals about 24 hours Noon is when the sun has reached its zenith, or highest point in the sky

Revolution Earth revolves around the sun in an elliptical orbit Its average distance from the sun is 150 million kilometers Earth’s distance from the sun varies

The Sun Sunlight comes from the sun to the Earth. The sunlight that warms our faces right now left the sun over eight minutes ago. The sun warms the Earth. The Sun is the center of the solar system Reaches 15 million Celsius Composed of hydrogen (70%) and helium (28%) It is almost a perfect sphere Eventually the sun will engulf Mercury, Venus, and Earth and become a red giant

The Sun Sunlight comes from the sun to the Earth. The sunlight that warms our faces right now left the sun over eight minutes ago. The sun warms the Earth. Sunlight comes from the sun to the Earth. The sunlight that warms our faces right now left the sun over eight minutes ago. The two major forms of energy the sun provides are thermal (heat) and light energy.

Night falls when our part of the Earth turns away from the sun Night falls when our part of the Earth turns away from the sun. The side facing away from the sun has nighttime.

Changing seasons One revolution around the sun equals 365 days. This revolution causes the changing of the seasons. When the Earth moves closer to the sun, summer returns. When the Earth moves farther away from the sun in its orbit, winter returns