Notes – the Moon

1. Notes – the Moon The Moon’s Motion • Revolves counterclockwise in an elliptical orbit, rising in the east and setting in the west • Revolution rate around Earth 27.3 days • Rotates on axis once every 27.3 days • So… the same side of Moon always faces Earth because rotation rate = revolution rate

2. The Moon’s Orbit • The Moon moves 130 along its orbit each day so after 24 hrs the Moon has not returned to the same spot in our sky because the Earth has been moving in its revolution around the Sun. • Causes the moon to rise and set 50 minutes later each day.

3. The Moon’s Orbit • Perigee - point in the Moon's orbit when it is closest to Earth • Apogee - point in the Moon's orbit when it is furthestfrom Earth

4. Moon Phases Daily changes in the Moon's appearance • Occur for 2 reasons:     1. Moon is seen due to reflected sunlight     2. Moon is in orbit around Earth • Waxing- Moon changes from New Moon to Full Moon, increasing in the amount of reflected light seen night after night • Waning - Moon changes from Full Moon to New Moon, decreasing in the amount of reflected light seen night after night

5. Lunar Month • Complete cycle of phases • Ex. Full moon to next full moon • Takes 29.5 days • Moon takes 2 days to catch up with Earth’s advance around the sun http://cygnus.colorado.edu/Animations/lunar2.mov

7. Newton’s Law of Gravitation • Between every two objects there is a force of attraction he called gravity. • Force of gravity between any 2 objects is related to the distance between the objects & the masses of the two objects Sir Isaac Newton England, 1642-1727

8. Newton’s 1st Law of Motion 1st Law (inertia) – an object in motion will remain in motion at the same speed and in the same direction unless acted upon by an outside force. • Inertia explain why planets don’t crash into the object they orbit • Gravity explains why planets don’t keep moving in a straight line forever; why they have an elliptical orbit

9. Earth & Moon Formation • Formed about 4.6 billion years ago • Earth/Moon forms almost a double planet for no other planet has a satellite as large in comparison to the size of the planet. • Earth formed by accretion from a nebula. • Differentiation of materials, allowed earth’s interior layers to form

10. Theories on the Origin of the Moon • The Earth and Moon formed at the same time. • The Earth was spinning so fast that a chunk of it spun off into orbit. • The Moon formed somewhere else in space and was later captured by Earth’s gravitational field. • The Moon formed as a result of a collision between the Earth and another planet sized object that released a huge amount of debris and rock that later condensed to form the Moon.

11. Scientists estimate that the Moon is 4.6 billion years old.

12. Properties of the Moon • The Moon has layers like the earth – core, mantle, and crust.

13. More Properties • The Moon’s diameter is ¼ that of the Earth’s • The Moon’s mass is 1/8 of Earth’s • The Moon’s density is 3.3 g/cm3 compared to Earth’s 5.5 g/cm3 • The force of gravity on the Moon is 1/6 of that on Earth.

15. Lunar Features: Maria • The darker colored basins and level plains, which formed when lava spewed to the surface through fractures made by large meteor impacts. Highlands • Appear brighter than maria because they are made lighter colored rocks that reflect more sunlight. Within the highlands are mountain ranges and many craters. Most of the mountain ranges lie at the edges of maria.

16. Tides • A tide is a major movement of the oceans that result from the gravitational attraction of the Moon.

17. Tides • Gravitational pull of the Moon stretches the water of the oceans, creating 2-bulges of water. One bulge is on the side of earth facing the Moon, the 2nd is on the other side. The bulge of water represents high tide.

18. There are 2-high and 2-low tides over a 24-hour period. Shorelines will experience 1-high tide when the tidal bulge that points toward the moon passes by; and a 2nd when the tidal bulge that points away from the moon passes by. Low tides occurs twice, 6 hours after each high tide in areas perpendicular to the tidal bulge.

19. A tidal cycle takes longer than 24 hours because the Moon traveled 1/30 (or 12 degrees) of the way in it’s orbit around Earth, so it takes an addition 50-minutes per day for the Moon to get back to over the same spot of Earth.

20. The Sun does have a gradational influence on Earth’s oceans but it is less than that of the Moon’s. This is because the Moon is much closer to Earth, it’s force is 2.4 times greater than the Sun’s.

21. Spring tides occur 2 times per month during a new and full moon. During these 2 phases the Sun, Moon, and Earth form a straight line, so the tidal pull of the Sun and the Moon are together, making high tides higher than usual and low tides even lower.

22. Neap tides occur 2 times per month during the 1st and 3rd quarters moon. During these 2 phases the Sun, Earth, and Moon form a right angle, so the tidal pull of the Sun and the Moon are pulling in opposite directions, making high tides lower than usual and low tides higher than usual.

23. High tides does not occur when the moon is directly overhead because the wave (tidal bulge) lag behind earth’s rotation. • Tidal bulges are always located on the sides of earth that point towards and away from the moon. The bulge moves slowly with the Moon. Tides occur because earth is rotating through or beneath the bulges. • When the tidal bulge hits a landmass, energy is lost by friction; which will release heat.

24. The tidal bulge affects Earth’s rotation by slowing Earth’s rotation down. • Additional factors that can affect tides are the size and shape of the continents shorelines and the shape of the ocean basins.

25. Tidal Range - the difference in level between high tide and low tide Ex. Bay of Fundy, Nova Scotia has a large range of 15m and the gulf of Mexico a small tidal range

26. Notes – Eclipses Eclipse - An astronomical event that occurs when one celestial object moves into the shadow of another. • Occurs when the moon is in direct alignment with the Sun and Earth – forming a perfect line. • Does not occur every month because the moon does not orbit the Earth in the same plane that the earth orbits the Sun

28. Lunar Eclipse • Earth’s shadow falls on the moon; Moon becomes darker and may appear red in color because the light from the sun is refracted around the Earth • Only the longest wavelengths (red & orange) make it.  • April 15, 2014         

29. Lunar Eclipse Cont’ • Anyone on the nighttime side of Earth can see a Lunar Eclipse. • Occurs only at Full Moon • Full Moon is usually above or below the Earth's umbra so no eclipse occurs

30. Solar Eclipse • When the moon moves directly between the Sun and Earth • Moon casts a shadow on part of the Earth. • Only people within the narrow band of the umbra see a full Solar Eclipse  

31. Solar Eclipse Cont’ • Occurs only at New Moon • Umbra – area of total shadow; person within it sees a total eclipse • Penumbra – area of partial shadow; person within it sees a partial eclipse • 3 Types of Solar Eclipses • Total • Partial • Annular