Earth’s Moon 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 What do we know already? * When have you seen the moon? * What does it look like? * Have you ever seen its craters? * Do the patterns of the craters ever change? The moon revolves around the earth with a period of about 29 2

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 Waning Moon – decreasing from full to new moon Waxing Moon – increasing from new to full moon

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 Midnight Midnight 6 pm 9

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 13

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.