1. Astronomy

2. Ch. 19 Earth, Moon, and Sun
This amazing Earthrise above the moon's horizon was seen by astronaut Michael Collins in the Apollo 11 moon orbiter Columbia.

3. Objectives Identify the effects of Earth’s rotation and revolution.
Explain the causes of the seasons on Earth.

4. 19.1 Earth in Space Discover Activity - p. 636
Why Does Earth Have Day and Night?

5. Introduction
Egyptian farmers planted their crops after the floods every year. They noticed that the star Sirius became visible before the floods. That’s when they could start predicting the floods.
The Egyptians were the first people to study the stars.

6. Days and Years
Astronomy is the study of the moon, stars, and other objects in space.

7. Rotation
Axis - the imaginary line that passes through Earth’s center and the North and South poles.
Rotation - the spinning of Earth on its axis.
A point on the equator rotates at about 1,600 km per hour.

8. Rotation Earth’s rotation on its axis causes day and night.
Earth rotates eastward.
It takes 24 hours to rotate once on its axis. This is called a day.

9. Revolution Earth also travels around the sun.
Revolution - the movement of one object around another object.
Earth’s orbit is a oval shape.

10. Calendars
The Egyptians counted the number of days between Sirius stars which was about 365.
Earth’s orbit around the sun is about 365 1/4 days.
Four years of 365 1/4 days each can be approx. by taking 3 years of 365 days and a fourth year of 366 days. This is known as leap year.
On a leap year, one extra day in February is added for 29 days.

11. Calendars Dividing the year into smaller parts (months) was difficult.
Early people used the moon cycle which is 29 1/2 days but this only added up to 354.
The Egyptians had a plan to have 12 months of 30 days and 5 extra days.
The Romans borrowed the calendar and devised the one that we have today with 11 months of 30 to 31 days and February with 28 or 29 days.

12. Seasons on Earth
Most places have four seasons: winter, spring, summer, and autumn.

13. Earth’s Tilted Axis
Earth has seasons because its axis is tilted as it move around the sun.

14. Earth in June
The north end of Earth’s axis is tilted toward the sun. It is summer in the Northern Hemisphere and winter in the Southern Hemisphere.

15. Earth in December
The south end of Earth’s axis is tilted toward the sun. It is summer in the Southern Hemisphere and winter in the Northern Hemisphere.

16. Both in June and December
Summer solstice - longest day of the year (June 21).
Winter solstice - shortest day of the year (December 21).
Both of the these are in the Northern Hemisphere and the opposite in the Southern Hemisphere.

17. Earth in March & September
Neither hemisphere is tilted toward or away from the sun. So the days and nights are in a equinox which is equal.

18. Earth in March and September
Vernal equinox, or spring equinox, occurs around March 21 and is the first day of spring.
Autumnal equinox, or fall equinox, occurs around September 23 and is the first day of fall.

19. Plants and Animals
Plants and animals are effected by the amount of day light hours.
In the spring and summer, plants grow, animals feed on the plants, insects and animals get more food.
In the winter, animals go dormant and birds travel to warmer climates to find food.

20. Reasons for the Seasons
Lab
Books, Styrofoam balls and flashlights.

21. Phases, Eclipses, and Tides

22. Objectives Describe the causes of the moon’s phases.
Explain what causes solar and lunar eclipses.
Identify the cause of the tides.

23. Engage/Explore
When does the moon appear?
Moon Rise and Set

24. Discover Activity
How Does the Moon Move?
Quarter & penny
P. 646

25. Motions of the Moon
The moon revolves around Earth and rotates on its own axis.
It takes 27.3 days to revolve around Earth.
The same side of the moon always faces the Earth.

26. Phases of the Moon
Phases of the moon are seen by the reflection of the sun on the moon’s surface.
The different shapes of the moon you see from Earth are called phases. The moon goes through its whole set of phases each time it revolves around the Earth, about once a month.

27. What Causes Phases?
Phases are caused by changes in the relative positions of the moon, Earth, and the sun.
P. 648

28. The Cycle of the Phases of the Moon

29. Eclipses
When the moon’s shadow hits Earth or Earth’s shadow hits the moon, an eclipse occurs.
Two types of eclipses:
solar and lunar

30. Solar Eclipse

31. Solar Eclipses
During a new moon, most of the time the moon is a little above or below the sun in the sky.
A solar eclipse occurs when the moon passes between Earth and the sun, blocking the sunlight from reaching Earth.
It is really a new moon that blocks your view of the sun.

32. Solar Eclipses

33. Total Solar Eclipses
Umbra - the darkest pat of the moon’s shadow that is cone-shaped. The point of the cone can reach a small part of Earth’s surface.

34. Partial Solar Eclipses
Penumbra - larger part of the shadow which is more visible on Earth. During a partial eclipse, part of the sun is visible.
It is not safe to look at a partial eclipse.

35. Solar Eclipse
August 11, 1999

36. Lunar Eclipses
A lunar eclipse occurs at a full moon when Earth is between the moon and the sun. Earth blocks sunlight from reaching the moon.

37. Total Lunar Eclipse
When the moon is in Earth’s umbra, you see a total lunar eclipse. You are more likely to see a total lunar eclipse than a total solar eclipse.

38. Partial Lunar Eclipses
Occurs when the moon passes partly into the umbra of Earth’s shadow. The edge of the shadow appears blurry and you can watch it pass across the moon for up to two or three hours.

39. Tides
Two high tides and two low tides occur daily, over 24 hours.

40. 19. 3 Rockets and Satellites

41. 19.4 Earth’s Moon

42. The End of Ch. 19