The Moon & Tides Chapters 22.2 & 16.2

Motions of the Earth-Moon System Orbital period = about one month The moon’s orbit is elliptical It is tilted 5 degrees off of Earth’s orbital plane

Perigee: Moon is closest to Earth Apogee: Moon is farthest from Earth Average distance from Earth to the moon = 384,000 km = 238,607 miles!

Phases of the Moon phases: various shapes of the moon lighted by reflected sunlight Brain Pop: Moon Phases

waxing: when the size of the visible portion of the moon is increasing waning: when the size of the visible portion of the moon is decreasing

new moon: no lighted area of the moon is visible from the Earth full moon: entire half of the side of the moon facing Earth is lit

crescent: less than half of the side facing the Earth is lit gibbous: more than half of the side facing the Earth is lit

New moon Waxing crescent 1st quarter Waxing gibbous

Full moon Waning gibbous Waning crescent 3rd quarter

Lunar Motions Synodic Month: The cycling of the moon through its phases (Apparent Motion) 29 1/2 days Basis for the first Roman calendar Siderial Month: The moon revolutionary period around the earth (Actual Motion) 27 1/3 days Occurs because Earth is revolving around the sun at the same time as the moon is revolving around The Earth!

27 1/3 days! Why does the same side of the moon always face us? Because the moon rotates and revolves at the same speed: 27 1/3 days!

Eclipses when one planetary body passes through the shadow of another Brain Pop: Eclipse

solar eclipse: when the moon is directly between the Earth and the sun

lunar eclipse: when the Earth is directly between the moon and the sun

Eclipses don’t occur every month because the moons orbit is tilted with respect to the Earth’s orbit

Tides Daily changes in the elevation of the ocean surface Brain Pop: Tides Result from gravitational attraction between… Earth, Moon, & Sun

               The earth has a uniform level of water all around it. 2 forces act on the water to produce tides…                                            The moon’s GRAVITY pulls on the earth, and the water bulges toward the moon.                                            Because the earth is spinning, there is a force pulling water in the opposite direction  INERTIA

The Result… As the earth turns upon its own axis in about 24 hours, a point on the earth moves through areas with these different forces acting on it.

Spring Tide – tides have greatest tidal range because the gravity of the sun & moon are combined

Neap Tide – daily tidal range is lower than average because the gravity of the sun & moon counteract each other

Tidal Patterns Diurnal - One high tide & one low tide each day                                       Semidiurnal - Two high tides & Two low tides each day

Tidal Graphing  One Day Multiple Days 