Earth s Moon. Origin and Properties of the Moon. The Moon s Motions

Transcription

1 Earth s Moon

2 Earth s Moon Origin and Properties of the Moon The Moon s Motions

3 Facts about the Moon We see the moon changes its appearances and position in the sky with approximately 30- day cycle. Unlike the stars, Moon can also be seen during the day. We also see that the Moon is always involved in eclipses, and Its position seems to be well correlated with the tide of the ocean. Understanding the motion of the Moon with respect to the Sun and the Earth will explain these phenomena. The Moon The moon revolves around the earth with a period of about 29 ½ days ~ one month!

4 Earth s Moon Origin and Properties of the Moon Scientists think the moon formed after a large object, about the size of a planet, hit Earth. 1. Earth is hit offcenter by a planetsized object. 2. The impact heats and deforms both bodies. Some rocky debris remains in orbit around Earth. 3. The debris ring, made of rock from the outer layer of both objects, gradually coalesces, forming the moon.

5 Impact theory Much of the material broken away from the earth goes into orbit. The moon reassembles in this orbit - it takes about a month of violent collisions. Earth is speeded up in rotation as a result of the collision. This theory is consistent with: 1.) composition of lunar rocks, which is similar to the composition of the crust of the earth; 2.) evidence that the moon had a molten surface for 200 million years; and 3.) the lack of magnetic field for the moon, which together with its low density implies it has very little iron in its core.

6 Earth s Moon The same side of the moon always faces Earth. Dark areas called maria are great basins and level plains on the moon. They are younger than the lighter lunar highlands. Lunar highland rocks are older than mare rocks. Maria: Extensive dark areas on the moon that represent great basins and level plains. Mare Highland

7 Earth s Moon Crater: A bowlshaped depression on the surface of a moon or a planet, usually caused by the impact of a meteorite. Most lunar craters were caused by the impact of meteoroids; rays of shattered rock and dust were splashed out by the impacts. Regolith is the loose rock material covering the moon s surface. It is formed as micrometeoroids smash into and erode the moon s surface. Micrometeoroid: Tiny rock fragment no larger than sand grains that travels through space. Lunar rocks have textures similar to Earth rocks but differ in composition.

8

9

10

11 The linked image cannot be displayed. The file may have been moved, renamed, or deleted. Verify that the link points to the correct file and location. Earth s Moon Rille: A trenchlike valley running through the bedrock of lunar maria, believed to have formed after the cave-in of the roof of a tunnel that had transported lava. Ray: A bright streak of shattered rock and dust that radiates from a lunar crater.

12 Why do we Always See the Same Side of the Moon? The rotation period of the Moon with respect to the universe is exactly the same as the rotation period of the Moon around the Earth. No! It s due to Tidal Locking Is this a coincidence?

13 Dark Side of the Moon The Moon doesn t have a dark side Everywhere on the Moon, the Sun rises and sets once per month It has a side which faces away from us During a New Moon, the far side is completely illuminated

14 The Moon s Motions A lunar eclipse occurs when Earth passes between the sun and the moon, and the moon is within Earth s shadow. Moon lunar eclipse Penumbra Sun Earth Umbra A solar eclipse occurs when the moon passes between the sun and Earth, and the moon s shadow falls on Earth. solar eclipse Sun Moon Earth Total Solar Eclipse

15 Eclipses Eclipses occur when the Sun, the Earth and the Moon all lie along a straight line They must line up in all 3 dimensions + time the Moon s orbit is tilted 5 o with respect to the ecliptic, so there are only two times a year when the paths overlap

16 Solar and Lunar Eclipses Eclipse: The total or partial obscuring of one celestial body by another The obscuration can be either One celestial body blocking the view to the other: Solar eclipse---moon blocking Earth s view to the Sun One celestial body is in the shadow of another: Lunar eclipse---moon is in the shadow of the Earth Lunar eclipse image from

17 Lunar Eclipse Umbra: The darkest part of the shadow cast by the moon or by Earth. Penumbra: The area of partial shadow surrounding the darkest part of the shadow of the Earth or moon. Lunar eclipses can only occur during a full moon. The maximum time a lunar eclipse can last is 3 hours and 40 minutes.

18 Solar eclipses can only occur during a new moon. The maximum time for a total solar eclipse is 7 minutes and 40 seconds. Solar Eclipse Solar eclipses are visible in a narrow path a maximum of 167 miles wide (269km.)

19 THE NEXT SOLAR ECLIPSE is a AUGUST 21, 2017 Bailey s Beads See Richard Monk s webpage on eclipses: astronomy/iau_eclipses/ Solar Corona Diamond Ring

20 Eclipses: Summary The parties involved: Sun, Moon, and Earth Motion of the Moon around Earth: ½ day revolution of the Moon around the Sun 2. Tilt (~5º) of the lunar orbit (around the Earth) w.r.t. the Ecliptic plane (Earth s orbital plane around the Sun) 3. The precession of the lunar orbit w.r.t. Earth-Sun direction Solar eclipse happens when the Moon is between the Earth and the Sun. The size and distance of the Moon need to be just right for us to see total eclipse. The changing distance between the Earth and the Moon explains the occurrences of the total and ring solar eclipses. The changing distance between the Earth and the Sun, and the Earth and the Moon explains the difference in the duration of the solar eclipses. Lunar eclipse happens when Earth is between the Moon and the Sun.

21 Eclipse facts The maximum time a lunar eclipse can last is 3 hours and 40 minutes. The maximum time for a total solar eclipse is 7 minutes and 40 seconds. Lunar eclipses can occur up to 3 times a year.

22 The Moving Ocean Tides The twice-daily rise and fall of Earth s oceans known as the tide is a result of gravitational pulls from the moon and the sun. Low tide Indirect high tide Direct high tide Moon s orbit Moon Uniform water level Low tide

23 The Moving Ocean Tides VOCABULARY tides perigee apogee The twice-daily rise and fall of Earth s oceans known as the tide is a result of gravitational pulls from the moon and the sun. Tides reach different levels depending on Earth s location in relation to the moon and sun. High tides are higher and low tides are lower when the moon, sun, and Earth are aligned. High tides are not as high and low tides are not as low as usual when the moon and sun are not in line with Earth.

24 Spring Tides The gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth. Moon Moon Earth Phase of of the moon? New Moon Phase of the moon? Full Moon Higher high tides and lower low tides

25 Neap Tides The gravitational affects of the moon and sun fight each other with their influence on the flow of the oceans on Earth. Moon Moon Phase of the moon? Phase of the moon? Third Quarter Third Quarter Earth Phase of the moon? First Quarter Moon Lowest high tides and highest low tides

26

27

28 The Lunar Program and Flagstaff

29

30

31

32

33

34

35

36

37

38 Two members of the prime crew of the Apollo 17 lunar landing mission participate in lunar surface extravehicular activity simulation training at the Kennedy Space Center, Florida.

39 Genesis Rock" returned by the Apollo 15 lunar mission

40 During the Apollo 12 mission in 1969, commander Pete Conrad retrieves equipment from the Surveyor 3 probe, which landed on the moon three years earlier. This picture, taken by astronaut Alan Bean, shows Apollo 12's lunar module in the far distance.

41

42

43

44 Apollo 17 astronaut Harrison Schmitt standing next to boulder at Taurus-Littrow during third extravehicular activity (EVA-3).

45 This photo was taken by Apollo 17 commander Eugene Cernan. It is of lunar module pilot Harrison Schmitt standing in front of a large split boulder on the Moon. Apollo 17 was the last of the Apollo Moon landing missions.

46