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1. The Moon Why does the Moon change in appearance at different times of the month? What is an eclipse, and why does it happen? What causes the sea level on Earth to rise and fall twice a day? In this presentation you will find out the answers to all of these questions, as we explore our nearest neighbor in space - the Moon. Next >

2. What is a Moon? A moon is a body that orbits (follows a path around) a planet. Sun Moon A planet is a body that orbits a star. In our solar system, the star is the Sun. Earth The Earth is a planet, and it has one moon. Because the Moon orbits the Earth, we say it is the Earth’s satellite. Next >

3. The Orbit of the Moon The Moon orbits the Earth once every 27.3 days. Sun The shape of the orbit is not a perfect circle, but an ellipse. An ellipse is an oval shape, like a stretched circle. Earth Next >

4. Axis Axis The Orbit of the Moon The Earth rotates on its axis every 24 hours. This causes day and night. The Moon also rotates on its own axis, but it is much slower than the Earth. The Moon rotates every 27.3 days, which is the same length of time that the Moon takes to orbit the Earth. Because of this, the same side of the Moon always faces the Earth. Before people began to explore space in the late 20th century, no one had ever seen the other side of the Moon. Next >

5. Diameter Characteristics of the Moon The Moon is much smaller than the Earth. The Moon’s diameter is approximately four times smaller than that of the Earth. It also has a much smaller mass than the Earth, so the gravitational pull of the Moon is much weaker. Because the Moon’s gravity has only one sixth of the strength of that of the Earth, the Moon does not have an atmosphere. This means that the Moon has no air or water, and therefore, cannot sustain life. Next >

6. Formation of the Moon No one knows exactly how the Moon was formed. However, rock samples brought back to Earth, show that the Moon and the Earth are about the same age. Many scientists believe that soon after the Earth formed, an object about the size of Mars collided with the Earth, throwing a large amount of debris into space. The debris eventually came together, forming the Moon. Next >

7. Question 1 Which of the following statements is true? A) The Moon orbits the Earth. B) The Earth orbits the Sun. C) The Moon takes 27.3 days to rotate on its axis. D) All of the above

8. Moon Cycles Although the Moon can often seem quite bright, it does not actually emit visible light. We can see the Moon because it reflects light from the Sun. Angles between the Earth, the Moon and the Sun change Sunlight can only reach the side of the Moon that faces the Sun. The other half of the Moon is in darkness. Light from the sun is reflected by the moon As the Moon orbits the Earth, and the Earth orbits the Sun, the amount of the Moon’s sunlit surface that faces the Earth changes. This is why the shape of the moon appears to change. Next >

9. Full Moon New Moon Moon Cycles When the Moon is between the Earth and the Sun, the bright side of the Moon is turned away from the Earth so we cannot see it. This is known as a New Moon. Waning Then, as the Moon orbits the Earth, the amount of the Moon that we can see increases each night. The Moon is said to be waxing. Waxing When the Moon has completed half of its orbit, the bright side of the Moon faces us. This is known as a Full Moon. As the Moon continues its orbit, the amount of the Moon that we can see decreases each night. The Moon is said to be waning. Next >

10. Lunar Eclipse A lunar eclipse occurs when a full moon passes into the shadow of the Earth. The Earth stops some of the sunlight from reaching the Moon, so the Moon becomes dim and appears to be a copper color. A lunar eclipse does not occur every time there is a full moon, because the Moon’s orbit around the Earth is slightly tilted. A lunar eclipse can last for more than an hour. Next >

11. Solar Eclipse A solar eclipse occurs when a new moon moves directly between the Sun and the Earth. The Moon blocks out the Sun, causing a shadow on the Earth. A solar eclipse does not occur every time there is a new moon, because the Moon’s orbit around the Earth is slightly tilted. Next >

12. North America Europe Asia North Atlantic Ocean North Pacific Ocean North Pacific Ocean Africa South America Indian Ocean Australia South Pacific Ocean South Atlantic Ocean Tides A tide is the rising and falling of the Earth’s oceans. Tides are caused by the combined gravitational forces of the Moon and the Sun on the water in the oceans. The size of gravitational force depends upon the mass of the object exerting the force, and its distance from the Earth. Distance has a greater effect on the size of the force than mass. Because the Moon is nearer to the Earth, it exerts more force on the water in the oceans than the Sun. Next >

13. Tidal Cycles The gravitational force of the Moon on the Earth pulls the water in the oceans toward the Moon. Earth Moon The effect of the force is strongest on the area of the Earth that is closest to the Moon, causing the water level to rise. This is called a high tide. Gravitational Force Opposite High tides At the same time, on the opposite side of the Earth, a similar high tide is seen. This is because the Earth is also being pulled toward the Moon, leaving behind the water furthest from the Moon. Next >

14. Question 2 "On the side of the Earth that is closest to the Moon, the Moon's gravitational force causes a rise in sea level. This is called a high tide." Is this statement true or false? Answer True or False.

15. Tidal Cycles As the Moon orbits the Earth, each ocean will experience a high tide twice in about 25 hours (one high tide approximately every 12.5 hours). For example, if high tide occurs at midnight, a second high tide will occur at around 12:30pm. In between the two high tides, there are two low tides a day. This happens when the water in the ocean has been pulled away by a high tide elsewhere. In the above example, low tides will occur at around 6:15am and 6:45pm. Next >

16. Neap tide Sun Moon Earth Spring tide 90 degrees Extra gravitational pull Spring and Neap Tides When the Sun and Moon are in line with the Earth, the gravitational force from the Sun combines with the gravitational force from the Moon. This causes the highest of the high tides, which is called a spring tide. When the Sun is at 90 degrees to the Moon, the gravitational force from the Sun pulls away from the gravitational force of the Moon. This causes the lowest of the high tides, which is called a neap tide. There are two spring tides and two neap tides each month. Next >

17. Question 3 Which of the following statements is NOT correct? A) A low tide occurs between two high tides. B) A spring tide happens when the Moon, Sun and Earth are in line with each other. C) A neap tide happens when the Moon and the Sun are at a 90 degree angle when viewed from the Earth. D) Spring and neap tides happen every week.

18. The Moon Cycle The amount of the Moon that we can see as it orbits the Earth is described in eight stages known as phases: 1. New Moon 2. Waxing Crescent 3. First Quarter 4. Waxing Gibbous 5. Full Moon 6. Waning Gibbous 7. Last Quarter (Third Quarter) 8. Waning Crescent The Moon cycle takes 29.5 days, so each phase occurs about once a month. Next >

19. 8 7 1 2 3 4 5 6 The Moon Cycle Waning Gibbous Last Quarter Waning Crescent New Moon Full Moon Earth Sun Waxing Gibbous Waxing Crescent First Quarter Next >

20. Question 4 The Moon cycle happens approximately every: A) month B) year C) day D) minute

21. Question 5 At which stage in the Moon cycle can we NOT see any reflection of the Sun's light on the Moon? A) Full Moon B) Waning Crescent C) Waxing Crescent D) New Moon

22. Summary After completing this presentation you should be able to: • show knowledge and understanding of the characteristics of the Moon • show knowledge and understanding of the interactions between the Moon, the Earth and the Sun End >