1. Earth, Moon, and Sun Earth in Space Gravity and Motion Phases, Eclipses, and Tides Earth’s Moon Table of Contents

2. Earth, Moon, and Sun What is Astronomy? Astronomy – the study of the moon, stars, and other objects in space

3. Earth, Moon, and Sun Where did it originate? One of the first theories about the solar system stated that the Earth, Sun, and Moon are all within a “celestial sphere” which has holes that allows light to come through from the heavens (stars).

4. Earth, Moon, and Sun Earth in Space For centuries astronomers have been studying the movements of the sun and the moon across the Earth Many astronomers believed that the Earth stood still while the sun moved across it.

5. Earth, Moon, and Sun How Earth Moves - Earth in Space Earth moves through space in two major ways: rotation and revolution.

6. Earth, Moon, and Sun Earth in Space Rotation – the spinning of the Earth on its axis Axis – the imaginary line that passes through the center of the Earth (on a 23.5º tilt) Revolution – the movement of one object around another (ie. the Earth around the sun) One complete revolution takes 1 year (365 1/4 days)

7. Earth, Moon, and Sun Earth in Space Calendars – are systems of organizing time and defines the beginning, length, and divisions of a year. They have been used for centuries. The earth follows an orbit (path) Misconception!! “The Earth’s orbit is NOT round but slightly elliptical.”

8. Earth, Moon, and Sun Sunlight Striking Earth’s Surface - Earth in Space Near the equator, sunlight strikes Earth’s surface more directly and is less spread out than near the poles.

9. Earth, Moon, and Sun The Seasons on the Earth Because of the way the sun’s rays hit the Earth, temperatures tend to be warmer in the tropics and cooler in the polar regions

10. Earth, Moon, and Sun The Seasons on the Earth There are 4 basic seasons on the Earth between the tropic and polar regions They include : Spring, Summer, Fall, and Winter The seasons occur because the Earth is tilted 23½° on an axis As the Earth revolves around the sun certain parts of the Earth receive more sunlight during certain times of the year

11. Earth, Moon, and Sun The Seasons on the Earth When it is summer in the Northern Hemisphere it is winter in the Southern Hemisphere and visa versa. In the Northern Hemisphere (where we live): March = Spring Equinox June = Summer Solstice September = Fall Equinox December = Winter Solstice (North axis is pointed away from the sun)

12. Earth, Moon, and Sun Seasons on Earth - Earth in Space Earth has seasons because it is tilted as it revolves around the sun.

13. Earth, Moon, and Sun Seasons on Earth - Earth in Space The height of the sun above the horizon varies with the season.

14. Earth, Moon, and Sun The Seasons on the Earth In June the north axis is pointed towards the sun The noon sun is high in the sky and there are more daylight hours In December the north axis is pointed away from the sun The noon sun is lower in the sky and there are less daytime hours

15. Earth, Moon, and Sun Graphic Organizer Around the sun revolves Earth On its axis Years rotates causing Night and day

16. Earth, Moon, and Sun The Seasons on the Earth A solstice is when the sun is either the furthest north or south of the equator. They occur June 21 (furthest north) and December 21 (furthest south) An equinox is when the noon sun is directly overhead at the equator. They occur March 21 and September 22. The word equinox means “equal night” because there are roughly 12 hrs of both day and night throughout the world on those dates.

17. Earth, Moon, and Sun Seasons Activity Click the Active Art button to open a browser window and access Active Art about the seasons. - Earth in Space

18. Earth, Moon, and Sun Gravity and Motion In the 17th Century Isaac Newton studied various forces (a push or pull on an object) One of these forces was gravity which is the force that attracts all objects toward each other. Newton called this the law of universal gravitation.

19. Earth, Moon, and Sun Gravity - Gravity and Motion The strength of the force of gravity between two objects depends on two factors: the masses of the objects and the distance between them.

20. Earth, Moon, and Sun Mass vs. Weight Mass is the amount of matter in an object Weight is the force of gravity pulling on an object Unlike mass that never changes an objects weight can change depending on location.

21. Earth, Moon, and Sun Gravity Versus Distance As a rocket leaves a planet’s surface, the force of gravity between the rocket and the planet changes. Use the graph to answer the following questions. - Gravity and Motion

22. Earth, Moon, and Sun Gravity Versus Distance Force of gravity on the rocket in millions of newtons and distance from the planet’s center in planetary radii Reading Graphs: What two variables are being graphed? In what units is each variable measured? - Gravity and Motion

23. Earth, Moon, and Sun Gravity Versus Distance Four million newtons Reading Graphs: What is the force of gravity on the rocket at the planet’s surface? - Gravity and Motion

24. Earth, Moon, and Sun Gravity Versus Distance One million newtons Reading Graphs: What is the force of gravity on the rocket at a distance of two units (twice the planet’s radius from its center)? - Gravity and Motion

25. Earth, Moon, and Sun Gravity Versus Distance It decreases. Making Generalizations: In general, how does the force of gravity pulling on the rocket change as the distance between it and the planet increases? - Gravity and Motion

26. Earth, Moon, and Sun Gravity and Inertia - Gravity and Motion Newton concluded that two factors– gravity and inertia – combine to keep the moon in orbit around Earth.

27. Earth, Moon, and Sun Gravity and Motion Inertia is the tendency of an object to resist a change in motion Ex: When a car stops suddenly the passengers continue to move forward Inertia is what keeps the Earth, moon, sun, and other planets from crashing into each other. Newton concluded that both gravity and inertia help keep the Earth in orbit around the sun and the moon in orbit around the Earth. He called this orbital motion.

28. Earth, Moon, and Sun Links on Gravity Click the SciLinks button for links on gravity. - Gravity and Motion

29. Earth, Moon, and Sun Motions of the Moon - Phases, Eclipses, and Tides The changing relative positions of the moon, Earth, and sun cause the phases of the moon, eclipses, and tides. It takes the moon 27.3 days to revolve around the Earth and 27.3 days to make one complete rotation….This means that we are always facing the same side of the moon (explains the “man in the moon” expression)

30. Earth, Moon, and Sun Phases, Eclipses, and Tides The moon appears bright because it reflects the sun’s light As the moon revolves around the Earth and the Earth revolves around the sun it creates different phases (shapes)

31. Earth, Moon, and Sun Phases of the Moon - Phases, Eclipses, and Tides The phase of moon you see depends on how much of the sunlit side of the moon faces Earth.

32. Earth, Moon, and Sun Phases of the Moon New Moon – the moon is between the sun and the Earth and not visible to us Waxing – when the visible portion of the moon is increasing Waxing-crescent – when the first sliver of the moon becomes visible after the new moon First quarter – follows the waxing-crescent when half of the moon facing the earth becomes visible

33. Earth, Moon, and Sun Phases of the Moon Waxing-gibbous – follows the first quarter when slightly more than half of the moon facing the Earth becomes visible Full moon – the Earth is between the sun and the moon and the entire side of the moon facing the Earth is visible Waning – when the visible portion of the moon is decreasing

34. Earth, Moon, and Sun Phases of the Moon Waning-gibbous - following the full moon when the visible part of the moon facing Earth is slightly larger than half Third(Last) quarter - follows the waning-gibbous when half of the moon facing the earth becomes visible Waning-crescent - when the last sliver of the moon becomes visible before the new moon

35. Earth, Moon, and Sun Phases of the Moon The period from one new moon to the next is 29.5 days. “Once in a blue moon….” A blue moon occurs when there are two full moons in the same month….does not happen very often.

36. Earth, Moon, and Sun

37. Moon Phases and Eclipses Activity Click the Active Art button to open a browser window and access Active Art about moon phases and eclipses. - Phases, Eclipses, and Tides

38. Earth, Moon, and Sun The Moon’s Orbit - Phases, Eclipses, and Tides The moon’s orbit is tilted about 5 degrees relative to Earth’s orbit around the sun.

39. Earth, Moon, and Sun Solar Eclipse - Phases, Eclipses, and Tides A solar eclipse occurs when the moon passes directly between Earth and the sun, blocking sunlight from parts of Earth.

40. Earth, Moon, and Sun Solar Eclipses Total Solar Eclipse – darkest part of the moon’s shadow (the umbra) blocks out the sunlight Partial Solar Eclipse – the lighter part of the moon’s shadow (the penumbra) blocks out the sunlight

41. Earth, Moon, and Sun Lunar Eclipse - Phases, Eclipses, and Tides During a lunar eclipse, Earth blocks sunlight from reaching the moon.

42. Earth, Moon, and Sun Lunar Eclipses Total Lunar Eclipse – darkest part of the Earth’s shadow (the umbra) blocks out the reflected light of the moon Partial Lunar Eclipse – the moon earth and sun aren’t completely in line causing the Earth’s shadow to cover only part of the moon

43. Earth, Moon, and Sun Tides - Phases, Eclipses, and Tides Tides occur mainly due to the difference in the force of gravity between the moon and different parts of Earth.

44. Earth, Moon, and Sun Spring and Neap Tides - Phases, Eclipses, and Tides When Earth, the sun, and the moon are in a straight line, a spring tide occurs. When the moon is at a right angle to the sun, a neap tide occurs.

45. Earth, Moon, and Sun The Moon’s Surface - Earth’s Moon Features on the moon’s surface include maria, craters, and highlands. The dark, flat areas on the moon’s surface are called the maria. The light-colored features that cover much of the moon’s surface are highlands.

46. Earth, Moon, and Sun The Moon’s Size - Earth’s Moon The moon is 3,476 km in diameter, a little less than the distance across the contiguous United States.

47. Earth, Moon, and Sun The Origin of the Moon - Earth’s Moon Scientists theorize that a planet-sized object collided with earth to form the moon.

48. Earth, Moon, and Sun Links on Earth’s Moon Click the SciLinks button for links on Earth’s moon. - Earth’s Moon

49. The Solar System Comets Comets – loose collections of ice, dust, and small rocky particles. –Have orbits that are usually very long, narrow ellipses. –Comets consist of three parts. Nucleus – solid center Coma – gas and dust surrounding the nucleus Tail – gas, ice, and dust trailing behind

50. The Solar System Structure of a Comet - Comets, Asteroids, and Meteors Most comets have two tails—a bluish gas tail and a white dust tail. The name comet means “long-haired star” in Greek

51. The Solar System Comet Orbits - Comets, Asteroids, and Meteors Most comets revolve around the sun in very long, narrow orbits. Gas and dust tails form as the comet approaches the sun.

52. The Solar System Asteroids Asteroid – rocky objects revolving around the sun. –Too small and numerous to be considered planets.

53. The Solar System Asteroids Asteroid belt – region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found. –Most are less than a kilometer, but some reach 300 kilometers in diameter. –Scientists believe a large asteroid struck the earth 65 million years ago, and it is probable that one will struck again in the future.

54. The Solar System Meteoroids Meteoroid – a chunk of rock or dust in space Meteor – a meteoroid that has entered the earth’s atmosphere and burns up. –Also known as a “shooting star” Meteorite – a meteoroid that passes through the atmosphere and hits Earth’s surface.

55. The Solar System Feature CometsAsteroids Comparing and Contrasting Origin Kuiper belt and Oort cloud Between the orbits of Mars and Jupiter Size Composition Comets, Asteroids, and Meteoroids Meteoroids Comets or asteroids Excluding the tail, about the size of a mountain Typically less than 1 km; some are more than 300 km in diameter Smaller than comets or asteroids Ice, dust, small rocky particles RockRock or dust - Comets, Asteroids, and Meteors Feature Comets Asteroids Origin Kuiper belt and Oort cloud Between the orbits of Mars and Jupiter Size Composition Meteoroids Comets or asteroids Excluding the tail, about the size of a mountain Typically less than 1 km; some are more than 300 km in diameter Smaller than comets or asteroids Ice, dust, small rocky particles RockRock or dust