1 The Sun/ Earth/ Moon Systems

2 I. Tools of Astronomy A. Radiation 1. Light is a common term for electromagnetic radiation, which are electric waves. 2. The human eye can only see some wavelengths these are called visible light.

3 3. Electromagnetic radiation (E radiation) is not just visible light but UV radiation, radio waves, microwaves, X- rays and gamma rays.

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5 4. UV light causes sunburns. 5. X-rays help doctors. 6. Electromagnetic radiation is classified by its wavelengths.

6 B. Telescopes 1. A human eye can only see so far. 2. A telescope has the ability to see past what the average eye can see. 3. Two different types of telescopes are used to focus visible light.

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8 4. Refracting telescope or refractors brings visible light to a focus. 5. Reflecting telescopes bring visible light to a focus with mirrors. 6. Reflectors are used the majority of the time.

9 C. Telescopes at Other wavelengths 1. Interferometry is the process of linking separate telescopes together so that they act as one telescope. 2. Astronomers often have to send their instruments into space to collect information they seek.

10 3. The hubble space telescope (HST), which was launched in 1990 and is expected to operate until HST was designed to obtain images.

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12 5. Space exploration was also sending spacecraft directly to the bodies being observed. 6. Robot Sojourner part of the Pathfinder probe to Mars.

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14 7. Probes are practical only for objects within our solar system, because the stars are too far away. 8. Exploring objects in space has been a top priority for scientists. 9. Most recent program began in 1981.

The space shuttle provides an environment for scientists to study the effects of weightlessness on humans, plants and the growth of crystals and other stuff. 11. The shuttle mission last a MAXIMUM of 17 days, long-term effects must be studied in space stations.

A new multi- country space station called the International Space Station (ISS) is the ideal environment to study the long-term effect of space.

17 II. The Moon A. Reaching for the moon 1. Astronomers have learned much about the moon from telescopic observations. 2. Most of our knowledge comes from the Lunar Prospector and Clementine and astronauts.

18 3. Lunar expeditions began in the late 1950 ’ s. 4. The first step was taken in 1957 with the Sputnik I by the Soviet Union. 5. In 1961 a Soviet man was the first human in space.

19 6. The US ’ s Project Mercury, Alan B. Shepard Jr. was the first American ’ s into space on May 5, On July 20, 1969 During the Apollo 11 mission, Neil Armstrong and Buzz Aldrin were the first to land on the moon.

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21 B. Lunar Properties 1. Earth ’ s moon is unique among all the moons in the solar system. 2. It is one of the largest moons, especially compared to the size of the planet it orbits.

22 3. Most moons are much smaller than the planet they orbit. 4. The orbit of the Moon is also unusual because the moon is farther from Earth than most moons are from the planets they orbit.

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24 C. The lunar Surface 1. The Lunar surface is dark. 2. The albedo of the moon, the amount of sunlight that its surface reflects, is very small, about 7%. 3. Earth has an albedo of 31%.

25 4. The physical surface of the Moon is very different from the earth. 5. There is no erosion on the moon. 6. Regions called highlands are light in color, mountainous, and heavily covered with craters.

26 7. Regions called maria are dark, smooth plains. 8. All of the craters on the Moon are impact craters formed when objects from space crash into the lunar surface. 9. The material blasted out during these impacts fell back to the surface as ejecta.

Some craters have long trails of ejecta called rays, that radiate outward. 11. Rays are visible on the moon as light- colored streaks. 12. Maria do have a few scattered craters and rills, which are valleylike structures.

The moon is made up of minerals similar to earth.

29 D. History of the moon 1. The entire lunar surface is very old. 2. Estimates between billion years old. 3. They think that moon was bombarded during its first 800 million years.

30 4. Which resulted in the breaking and heating of rocks on the surface of the moon. 5. This formed a layer of loose ground up rock called regolith. 6. The Maria slightly younger than the highlands are between billion years old.

31 E. Tectonics on the moon? 1. Mountain ranges around maria were not formed tectonically. 2. Some think that the moon has layered structures like the crust, upper mantle, lower mantle and core. 3. Seismometers measure moonquake strength and frequency.

32 4. It is thought that the moon is not tectonically active. 5. The fact that the moon has no active volcanoes supports this theory

33 F. Formation theories 1. Capture theory- as the solar system was forming, a large object ventured too near to the forming earth, becoming trapped in its gravitation pull and this is our moon.

34 2. Problem with this theory- something would have had to slow down the passing object to become trapped. 3. Another problem- the moon and earth are composed of very similar elements. If the moon had been captured you would think they would have DIFFERENT elements.

35 4. Simultaneous formation theory- the moon and earth formed at the same time and in the same general area. 5. Problem- different amounts of iron on Earth and on the moon. The moon is iron poor and the earth has tons of it. 6. The most commonly accepted theory- the impact theory.

36 7. Impact- the moon formed as a result of a gigantic collision between earth and mars about 4.5 billion years ago. 8. As a result of the collision, materials from the incoming body and from Earth ’ s outer layers were ejected into space, where they then merged together to form the moon.

37 9. Heat produced by the impact would have evaporated any water present on the moon.

38 III. The sun-earth-moon system A. Daily Motions 1. The most obvious pattern is rising and setting of the sun. 2. The sun rises in the east and sets in the west as do the moon, planets and stars.

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40 3. The sun, moon, planets and stars do not orbit around the earth every day. 4. It only appears that way to us because we observe the sky from a planet that rotates once every day.

41 B. Earth ’ s rotation 1. The length of a day as we observe it is a little longer than the time it takes Earth to rotate once on its axis.

42 C. Annual motions 1. Annual changes are the result of Earth ’ s orbital motion around the Sun. 2. The plane in which earth orbits about the sun is called the ecliptic. 3. At one point the earth ’ s axis is tilted toward the sun while the other is tipped away from the sun.

43 4. Our seasons are created by this tilt and by the Earth ’ s orbital motion around the sun. 5. Summer solstice the Sun is directly overhead at the tropic of cancer around June 21 st. 6. The winter solstice the sun is directly overhead at the tropic of Capricorn this is around December 21 st each year.

44 7. There is also autumnal equinox and vernal equinox. 8. Equinox means equal nights.

45 D. Phases of the moon 1. The moon does not emit visible light, instead we see the moon ’ s reflection of the sun ’ s light.

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47 2. Scientists theorize that Earth ’ s gravity slowed the moon ’ s original spin until the moon reached synchronous rotation the state at which its orbital and rotational periods are equal. 3. One of the moons effects on earths the formation of tides.

48 4. The moon ’ s gravity pulls on earth along an imaginary line connecting earth and the moon, and this creates bulges of ocean water on both the near and far sides of earth. 5. Earth ’ s rotation also contributes to the formation of tides.

49 E. Solar eclipses 1. A solar eclipse occurs when the moon passes directly between the sun and earth and blocks our view of the sun. 2. The sun is much larger than the moon, it is much farther away also which causes the sun and moon to be the same size.

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52 3. Solar eclipse does not happen every month. 4. The closet point in the moon ’ s orbit to earth is called perigee, and the farthest point is called apogee. 5. When the moon is near apogee, it appears smaller as seen from earth.

53 6. This is called an annular eclipse because from earth, a ring of the sun called an annulus is visible around the moon. 7. A lunar eclipse occurs when the moon passes through the Earth ’ s shadow. 8. This can happen only at the time of a full moon, when the moon is in the opposite direction from the sun.

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55 9. During a total lunar eclipse, the moon is faintly visible, because sunlight that has passed near earth has been refracted by earth ’ s atmosphere. 10. The maximum number of eclipses, solar and lunar combines that can be in a year is seven.

The last time this occurred was in 1982 and it won ’ t happen again until (How old will you be in 33 years?)

57 The End