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The Moon's Orbit and Rotation

MOON PHASES: Tonight's Moon phase (Image courtesy of U.S. Naval Observatory ). (Click on the link to get the Moon phase for any day). . The Moon's Orbit and Rotation .

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The Moon's Orbit and Rotation

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  1. MOON PHASES: Tonight's Moon phase (Image courtesy of U.S. Naval Observatory). (Click on the link to get the Moon phase for any day).

  2. The Moon's Orbit and Rotation The Earth's Moon is the fifth largest in the whole solar system, and is bigger than the planet Pluto. The Moon has a nearly circular orbit (e=0.05) which is tilted about 5° to the plane of the Earth's orbit. Its average distance from the Earth is 384,400 km. The combination of the Moon's size and its distance from the Earth causes the Moon to appear the same size in the sky as the Sun, which is one reason we can have total solar eclipses. It takes the Moon 27.322 days to go around the Earth once. Because of this motion, the Moon appears to move about 13° against the stars each day, or about one-half degree per hour. If you watch the Moon over the course of several hours one night, you will notice that its position among the stars will change by a few degrees. The changing position of the Moon with respect to the Sun leads to lunar phases. Have you ever heard the term the 'far-side' of the Moon? Because of the effect on the Moon of tidal forces due to the Earth, the same side of the moon always faces the Earth. In other words, it takes the Moon the same amount of time to rotate around once as it does for the Moon to go around the Earth once. Therefore, Earth-bound observers can never see the 'far-side' of the Moon. Tidal forces cause many of the moons of our solar system to have this

  3. Why Don't we have a Lunar Eclipse Every Month? • Lunar eclipses can only happen when the Moon is full and it passes behind the Earth and into its' shadow. But that brings to mind a question. It would make sense to think that because we have a full moon every month that we should also therefore have a lunar eclipse every month. • If the Moon's orbit around the Earth were in the same plane as the Earth's around the Sun (the ecliptic,) we would indeed have a monthly eclipse. However, the Moon's orbit is inclined about 5 degrees to the Earth's orbit. The Moon passes through the ecliptic only twice a month at a pair of points called the nodes. The rest of the time the Moon is either above or below the plane of the Earth's orbit and does not pass directly through the Earth's shadow.

  4. The Moon is not only acted on by its' gravitational bond with the Earth, the Sun also plays a part by trying to flatten out the Moon's orbit so that it is on the ecliptic. This makes the Moon "wobble" on its' axis just like the Earth does. The effect is like that of a spinning top. Because of gravitational interaction with the Sun, the line of nodes of the Moon's orbit moves over time, taking 18.6 years to make a complete cycle. This 18.6 year sequence of eclipses is called the saros cycle and during this cycle solar and lunar eclipses occur about every six months. The exact dates of the eclipses change and do not repeat for that 18.6 year cycle. • The change in the line of lunar nodes does more than just affect when eclipses occur. It also affects changes in the northern and southern extremes of the Moon as we view it by plus or minus five degrees. The farthest north of the celestial equator that the moon can be is 23 1/2 degrees plus the 5 degree inclination of the lunar orbit or 28 1/2 degrees. The farthest south, similarly, is -28 1/2 degrees. As an example, If your celestial equator is about 50 degrees up from the southern horizon, that means the Moon's height can change from as high as 78.5 degrees from the horizon to 21.5 degrees. That produces changes in the length of a moonlit night, making them longer or shorter depending on whether the Moon is at a northern or southern extreme. • It is interesting to note that the saros cycle was noticed by ancient cultures. The ancient Egyptians recorded the saros, but they didn't understand what caused it. They did realize that this wobbling was directly linked to eclipses. It was they who gave the saros its' name, and correctly observed its' period of 18.6 years.

  5. Introductionhttp://tycho.usno.navy.mil/vphase.html • Let's start with some basics. The Earth orbits the Sun while the Moon orbits the Earth. • The Earth also rotates about its axis once every 24 hours making an Earth day 24 hours long. • The Moon also rotates about its axis. • However, due to gravity, the Moon's rotation is such that the same side of the Moon always points towards Earth. • Since the Moon orbits the Earth approximately once every 28 days and since the same side of the Moon always points towards Earth, the Moon only rotates once every 28 days. • Meaning a Moon day is actually 28 Earth days long!

  6. Remember that the Moon orbits the Earth once every 28 days. So, every night the moon is in a slightly different place from where it was the night before. Since the Sun does not change its position (it is at the center of the solar system after all). The part of the Moon facing the Sun (where it is daytime on the Moon) slowly changes from night to night. • Since the Sun will only light up the sides of the Earth and Moon that are facing the Sun, the sides that are not facing the Sun will be very dark. So, From a spaceship flying above the solar system, it would look something like this: Space view looking down on the north pole. Earth rotates CCW, Moon orbits CCW. Space view with sick figure.

  7. NEW MOON • Let's look at 4 of the phases of the Moon starting with a New Moon. During a New Moon the Moon is on the same side that the Sun is. So, we can only see the dark side of the Moon. However, since the dark side is very dark it looks like there is no Moon at all. So remember "New Moon means dark Moon." Space view of New Moon. New Moon as seen from Earth.

  8. FIRST QUARTER • During a First Quarter phase the Moon has moved along side the Earth and we can now see the lighted side of the Moon that is facing the Earth (remember the dark side of the Moon is too dark to see). Since the lighted side is always only half of the Moon and since we can only see half of the lighted side, this is called the First Quarter (First Quarter the New Moon). • Space view of First Quarter • First Quarter as seen from Earth.

  9. Full Moon Space view of Full Moon Full Moon as seen from Earth. • During a Full Moon the Moon is on the same side of the Earth as we are. So, we can now see the entire lighted side of the Moon.

  10. Third or Last Quarter • During a Last Quarter phase the Moon has moved along side Earth's other side and we can once again only see half of the lighted side of the Moon. Therefore, this phase is called the Last Quarter (Last Quarter the New Moon). Space view of Last Quarter Last Quarter as seen from Earth.

  11. Phases of the Moon Movie • In actuality there are 8 phases and night by night the Moon slowly moves from 1 phase to another phase over the 28 day cycles. Thus, it takes about 4 days for the Moon to change from 1 phase to another. The moon wobbles and changes size. This is because the Moon's orbit around the Earth is not a circle and at times the Moon is close to the Earth and at other times farther away from the Earth. http://aa.usno.navy.mil/graphics/Moon_movie.gif

  12. Earth can be seen at a distance of around 114 million miles in an image taken by Nasa's Messenger spacecraftRead more: http://www.dailymail.co.uk/sciencetech/article-1305422/Incredible-image-Moon-orbiting-Earth-taken-Nasa-probe-114-million-miles-away.html#ixzz2MWmw2cAw

  13. The moon challenge game • http://sciencenetlinks.com/interactives/moon/moon_challenge/moon_challenge.html

  14. http://www.backyard-astro.com/blog/index.php/weblog/comments/2006_02_201/http://www.backyard-astro.com/blog/index.php/weblog/comments/2006_02_201/

  15. Great Links! • FRAME OF REFERENCE • http://www.physics-chemistry-interactive-flash-animation.com/mechanics_forces_gravitation_energy_interactive/frame_of_reference_motion_child_ball_train.htm • Mercantile Projection • http://www.nationalatlas.gov/articles/mapping/a_projections.html#one • THE Earth. Revolve, Rotate, Seasons • http://www.engineeringinteract.org/resources/astroadventure/flash/concepts/earth.htm • Earth and Space • http://resources.woodlands-junior.kent.sch.uk/revision/science/space.htm • The Earth and Beyond • http://www.childrensuniversity.manchester.ac.uk/interactives/science/earthandbeyond/matchingpairs/ • http://www.universetoday.com/75848/why-can-we-see-the-moon-during-the-day/ • (why can we see the moon during the day)

  16. Great Links! • http://www.das.uchile.cl/~mhamuy/moon.html • (go to part 2 lunar phases) • http://www.huffingtonpost.com/2012/10/30/ocean-of-storms-moon_n_2044627.html#slide=more207489 • (ocean of storms far side) • http://cosmiclog.nbcnews.com/_news/2013/03/02/17160360-meteor-lurked-for-thousands-of-years-before-blasting-russia-experts-say?lite • http://www.lpi.usra.edu/education/explore/marvelMoon/resources/videos.shtml • Find the moon phase on your birthday! • http://www.naturalist.net/Moon_Phases_through_time.htm • http://www.amnh.org/explore/ology/astronomy • (our place in space)

  17. Latitude and Longitude Practice Game • http://www.kidsgeo.com/geography-games/latitude-longitude-map-game.php Coordinate Pair Graphing Game http://www.mathplayground.com/locate_aliens.html

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