Warmup 1/7/12 Put the following in the correct order: Air expands due to lower pressure Warm air rises Condensation occurs and a cloud forms Air cools until it reaches the dewpoint Imagine you have decided to build a house on the Outerbanks of NC. Considering that your house is likely to experience a hurricane, what could you do to prevent damage from storm surge?

Earth’s Moon http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=6&cad=rja&ved=0CFwQFjAF&url=http%3A%2F%2Fsprott.physics.wisc.edu%2Flectures%2Fseasons.ppt&ei=bcrqUJSqM8rU0gGU0ICAAQ&usg=AFQjCNF_65WObx5mU5uNHps5-xurQOc0aA&bvm=bv.1355534169,d.dmQ 1.1.2 a Describe daily changes due to rotation, seasonal changes due to the tilt and revolution of the Earth, and tidal impact due to the gravitational interaction between the Earth and moon. 1.1.2b Develop a cause and effect model for the shape of the Earth explaining why the circumference around the equator is larger than that around the poles.

The Moon 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 revolves around the earth with a period of about 29 ½ days ~ one month!

Origin and Properties of the Moon 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 off-center by a planet-sized 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.

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. Impact theory

The Moon’s Motions Earth’s Moon The moon’s orbit is tilted 5 degrees relative to the plane of Earth’s orbit. The moon’s movement around Earth causes it to rise later each day and to go through phases. Light from the Sun Waning Crescent Waxing Crescent New Moon Full Moon Waning Gibbous Waxing Gibbous Last Quarter First Quarter Phases of the Moon

Lunar Phases Sunlight illuminates half of the Moon it’s a ball and the Sun is shining on it from one direction This causes the “phases” of the Moon Waxing Moon – increasing from day to day Waning Moon – decreasing from day to day

Lunar Phases (cont) New Moon Full Moon Waxing Crescent Moon Waxing Half Moon Waxing Gibbous Moon Full Moon Waning Gibbous Moon Waning Half Moon Waning Crescent Moon … New Moon The Moon is on the same part of the sky as the Sun and rises and sets with the Sun Full Moon The Moon is in the opposite side of the sky as the Sun and rises when the Sun sets and sets when the Sun rises

The Phase of the Moon The phase of the Moon depends on the relative position between the Sun, the Earth, and the Moon…

The time the Moon rises and sets is correlated to its phase Moonrise/Moonset The time the Moon rises and sets is correlated to its phase Phase of the Moon Rise Zenith Set New Moon 6 am 6 pm Waxing Half Moon Full Moon Waning Half Moon Noon Noon Noon Midnight Skip for today Midnight Midnight 6 pm

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. Is this a coincidence? No!  It’s due to Tidal Locking

Tidal Locking A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner. This synchronous rotation causes one hemisphere constantly to face the partner body. The Moons orbital period is 27.3 days. It also rotates once on its axis in 27.3 days (synchronous rotation) resulting in Tidal Locking.

“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

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

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 5o with respect to the ecliptic, so there are only two times a year when the paths overlap

Solar Eclipse Forecast Solar eclipses from 2004 to 2030 Knowing the orbit of the Earth and the Moon, we can now calculate the time and path of solar eclipses with great accuracy.

Eclipses: Summary The parties involved: Sun, Moon, and Earth Motion of the Moon around Earth: 29 ½ day revolution of the Moon around the Sun Tilt (~5º) of the lunar orbit (around the Earth) w.r.t. the Ecliptic plane (Earth’s orbital plane around the Sun) 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.

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. Uniform water level Moon Moon’s orbit Low tide Direct high tide Indirect high tide

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. 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.

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

Lowest high tides and highest low tides 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 Phase of the moon? Moon Phase of the moon? Third Quarter Third Quarter Earth Phase of the moon? Moon First Quarter Lowest high tides and highest low tides

Tides Perigee: The point closest to Earth in the moon’s orbit. Apogee: The point farthest to Earth in the moon’s orbit. Same gravitational force makes the Earth wider in the middle than at it’s poles (aka sphere)

We see a permanent "near" and "far side" of the Moon. Tides & Consequences This little tidal behavior goes both ways! The Earth rises tides on the Moon. The Earth "brakes" the Moon's rotation AND the braking is complete! Synchronous Rotation of the Moon and its orbital period! (27.3 days!) We see a permanent "near" and "far side" of the Moon. Moon also brakes the Earth's Rotation The length of the "day" is increasing! From fossil reef corals of about 4´108 years old - daily growth/annual growth  400 days/year ~ 22 hours a day! Day is increasing about 0.001 seconds/century. Moon's orbit is growing because of all of this interaction. Therefore, the day is getting longer, Moon looks smaller, and tides are weakening.