phases tides Solar eclipses Lunar eclipses The Moon gives us…

The moon’s surface The moon has 2 main surface features long recognized from Earth maria highlands

The lunar highlands represent the moons battered original crust

The maria are younger and represent lava filled basins formed from impact shortly after the moon formed Mare is the singular form for maria

Here is a very large impact crater on the maria over 3 billion years old Why do lunar surface features like craters last so long on the moon?

Phases

Waxing crescent 1 st quarter Waxing gibbous

Full moonWaning gibbous Last quarterLast crescent And the rest of the phases

What causes these phases? The moons orbit around earth 3 A.M. 9 P.M.3 P.M. 9 A.M.

Because the moon rotates in exactly the same period as It revolves, the same side of the moon always faces earth The moon therefore has a hidden side which is not the same as the dark side This hidden side was never seen by man until the late 1960’s when Apollo spacecraft first orbited the moon

So a phase is simply the portion of the lit half of the moon that faces The earth at any point during the moons orbit. If the earth did not rotate, an observer could watch the moon slowly move eastward through the stars (0.55 degrees every hour) east west east

A consequence of this is the moon rises 50 minutes later each night and there is a 50 minute delay each day in high tide East horizon Current moon position Moon’s position 24 hours ago 13 degrees apart Each day the moon is 13 degrees east of where It was

Because the earth also orbits the sun there is a small difference between the time for a true orbit of the moon once around the earth and the time to complete the phases (360 deg. Orbit) 27.3 days 29.5 days True orbit period = 27.3 days Month of phases = 29.5 days

Lunar Eclipses

A lunar eclipse occurs when the earth’s shadow falls on the moon. If the moon is completely within the earth’s shadow it is called A lunar eclipse. The 2 conditions needed for a lunar eclipse are: 1.Full moon 2.Moon crossing ecliptic (earth’s orbit plane)

Moon almost totally eclipsed The red color is from light bent onto the moon by earth’s atmosphere. Red light waves bend more than the others

Solar Eclipses

A solar eclipse occurs when the moons shadow falls on the earth Sometimes the moon’s shadow does not reach the earth and a different kind of solar eclipse occurs called an annular eclipse What could cause the moons shadow to sometimes not reach the earth? Yes, if the moon’s distance from the earth is too great, the shadow will not reach the surface. Remember the moon orbits the earth In an ellipse.

The dark inner part of the moon’s shadow is called the umbra Conditions needed for a total solar eclipse are: 1.Moon in new phase 2.Moon crossing ecliptic (earth’s orbit plane) 3.Moon at near point in it’s orbit (perigee)

Diamond ring effect just Before totality Totally eclipsed Moon with corona showing

Annular eclipse in upstate NY in 1994

Tides : Ebb and Flow

Actually the moon pulls more on more massive objects, as a result The Empire State Building is pulled 26 cm. closer To the moon at high tide Tides

A high tide occurs on the side facing the moon and on the opposite side High tide High tide North pole Low tide (direct) (indirect)

Because the moon moves 6.5 degrees in about 12 hours The indirect high tide will be 12 hours and 25 minutes after the direct high tide High tide High tide North pole Low tide (direct) (indirect) Moon 12 hrs. later Likewise the next direct high tide will be another 12 hours and 25 minutes after the indirect high tide, or 50 minutes later than the day before.

As with the moon rise, high tide is delayed 50 minutes each day due to the moons orbit of 13 degrees to the east during 24 hours Actually the time between high tides is 12 hours and 25 minutes And the time between a high and a low tide about 6 hours and 12.5 minutes

Spring tides Neap tides Higher high Tides and Lower low tides Minimum Range Between High and Low tide

Conditions that effect tide height Phase of the moon (spring or neap) Distance moon is from earth (perigee or apogee Local atmospheric pressure Local topography of sea floor (of course this is fixed)