3 Astronomy: The study of the moon, stars, and other objects in space. 8-4.4 Explain the motions of Earth and the Moon and effects of these motions as they orbit the Sun (including day, year, phases of the Moon, eclipses, and tides.VOCABULARY WORDSAstronomy: The study of the moon, stars, and other objects in space.Axis: The imaginary line that passes through Earth’s center and the North and South poles.
4 It is day on the side of Earth facing the sun. What is a Rotation?When earth spins on its axis this is called its rotation.- A point on the equator will rotate at about 1,600 km per hour.- Earth’s rotation on its axis causes day and night!It is day on the side of Earth facing the sun.It takes the earth 24 hours to rotate ONCE on its axis.
5 - Earth’s path as it revolves around the sun is called its orbit. What is a Revolution?In addition to rotating on its axis, Earth travels around the Sun. The movement of one object around another object is called revolution.- Earth’s path as it revolves around the sun is called its orbit.- Earth’s revolution around the sun is called a year! 365 ¼ days
6 WHAT ARE SEASONS?What two factors cause the season?
7 Seasons on EarthIt is warm near the equator because sunlight hits Earth’s surface directly and is less spread out. Why is it colder near the poles?Most direct sunlightEarth has seasons because its axis is tilted as it moves around the sun.What if the Earth’s axis were straight up and down relative to the sun, what would the seasons be like?
10 EARTH’S AXIS- When the north end of Earth’s axis is tilted toward the sun, the Northern Hemisphere has summer- When the north end of Earth’s axis is tilted away from the sun, the Northern hemisphere has winter, therefore getting less direct sunlight.The one on the rightWHICH ONE OF THE GLOBES WOULD BE SUMMER IN THE NORTHERN HEMISPHERE?
11 - One in spring around March 21 – Vernal (Spring) Equinox EARTH’S AXISVernal and Autumnal Equinox – they are the half way times between the solstices, neither hemisphere is tilted toward or away from the sun.- One in spring around March 21 – Vernal (Spring) Equinox- One in the fall around September 21 – Autumnal (Fall) EquinoxThe one on the leftWHICH ONE OF THE GLOBES WOULD BE THE AUTUMNAL EQUINOX OR THE VERNAL `EQUINOX?
12 Fun Fact-Earth’s orientation in space changes with time Fun Fact-Earth’s orientation in space changes with time. Its axis now points toward Polaris, The North Star, in about 12,000 years it will point toward Vega. This change is the result of Earth’s slow wobble on its axis.
13 JUNE AND DECEMBER ….SOMETHING TO REMEMBER!! Solstice – When the sun is overhead at either 23.5 degrees south or 23.5 degrees north of the equator.- The day when the sun is overhead at 23.5 degrees south is the WINTER SOLSTICE in the Northern Hemisphere. Around December 21- The day when the sun is overhead at 23.5 degrees north is the SUMMER SOLSTICE in the Northern Hemisphere. Around June 21
15 Review -Explain the process that causes day and night?Earth rotates on its axis once per day. As Earth rotates, half its surface is facing the sun (day) and half is facing away from the sun (night)What two factors cause the cycle of the seasons?The cycle of the seasons is caused by Earth’s revolution around the sun AND the tilt of Earth’s axis.Compare rotation and revolution.Rotation is turning around a point or an axis; revolution is movement around another object.What do the words solstice and equinox mean? How are they related to the position of Earth’s axis?A solstice is a day when the noon sun is overhead at 23.5 degrees south or 23.5 degrees north. This occurs when one end of Earth’s axis is tilted most directly toward the sun. Equinox means “equal night,” and occurs when neither pole of Earth’s axis is tilted toward the sun.Are changes in the distance between Earth and the sun important in causing the cycle of the seasons?The tilt of Earth’s axis, not its distance from the sun, is the cause of the cycle of seasons.
16 IF YOU KNOW IT…. RAISE YOUR HAND AND SHOW IT!! When it is winter in the Northern Hemisphere, which areas on Earth get the most concentrated amount of light?When it is summer in the Northern Hemisphere, which areas on Earth get the most concentrated amount of light?