ASTRONOMY: Earth and Space Systems

1. ASTRONOMY: Earth and Space Systems Standard 8-4: You will demonstrate an understanding of the characteristics, structure, and predictable motions of celestial bodies. 2/2/07

3. 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. 2/5/07 VOCABULARY WORDS Astronomy: The study of the moon, stars, and other objects in space. Egyptians were among the first people to study the stars Axis: The imaginary line that passes through Earth’s center and the North and South poles.

4. 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. 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!

6. Seasons on Earth It 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 sunlight Earth 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?

8. 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. WHICH ONE OF THE GLOBES WOULD BE SUMMER IN THE NORTHERN HEMISPHERE?

9. EARH’S AXIS WHICH ONE OF THE GLOBES WOULD BE THE AUTUMNAL EQUINOX OR THE VERNAL EQUINOX? Vernal 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 Equinox - One in the fall around September 23 – Autumnal Equinox

13. JUNE AND DECEMBER ….SOMETHING TO REMEMBER!! Solstice – When the sun is overhead at either 23.5 degrees south or 23.5 degrees north. - 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

14. Page J21 Review - 1. 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) 2. 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. 3. Compare rotation and revolution.Rotation is turning around a point or an axis; revolution is movement around another object. 4. 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. 5. 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.

15. 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?