THE SUN, EARTH, AND MOON

What causes day and night on Earth? Period of ROTATION – the amount of time it takes an object to make one complete circle on its axis (Earth rotates from West to East in 24 hours). The rotation of the Earth causes day and night. Period of REVOLUTION – the amount of time it takes an object to travel completely around the Sun (Earth travels counterclockwise around the Sun and its period of REVOLUTION is 365 days) How old are you? How many times have you revolved around the Sun!!

Seasons

Why is the Earth not the same temperature all over its surface? Because the surface of the Earth is curved, the poles receive less energy from the Sun as its beam of light is spread out over more surface area http://kentsimmons.uwinnipeg.ca/16cm05/1116/16biomes.htm

What causes the seasons on Earth? December Solstice (21st or 22nd) – Earth tilted away from the Sun; in the Northern Hemisphere, days are shortest and nights are longest June Solstice (20th or 21st) – Earth is tilted toward the Sun; in the Northern Hemisphere, days are longest and nights are shortest March (20th or 21st) and September (22nd or 23rd) Equinox – equal hours of day and night The Earth experiences seasons due to the 23.5˚ tilt of its axis and it’s motion around the sun. Earth’s elliptical orbit brings it closer to the Sun in the Winter than in the Summer!

Sun’s Path Across the Sky The apparent path of the Sun across the sky changes depending on the season

The Moon

Formation of the Moon The accepted hypothesis is that a large object collided with Earth sending large amounts of rock into Earth’s orbit The rocks clumped together to form the Moon

The Moon’s Surface Craters Rays formed by objects impacting the Moon’s surface millions of years ago Rays light-colored streaks extending out from craters

The Moon’s Surface Maria Highlands large, dark, flat areas formed from cooling lava flows Highlands the oldest parts of the Moon’s surface covered with craters

The Moon’s Motion The Moon revolves around the Earth every 27.3 days The Moon also rotates every 27.3 days Since the moon’s revolution and rotation are the same, the same side of the Moon always faces the Earth

Phases of the Moon more of the Moon’s near side is lit each night Waxing Phases Waning Phases more of the Moon’s near side is lit each night First Quarter – western side is lit Full Moon – entire near side is lit less of the Moon’s near side is lit each night Third Quarter – eastern side is lit New Moon – entire near side is dark

Phases of the Moon Diagram While the Sun always illuminates the Moon, we can only see a certain portion of the illuminated side depending upon where the Moon is in its orbit around the Earth

Eclipses and Tides

Solar Eclipse SOLAR ECLIPSES happen when the Moon is between the Earth and Sun and the Moon’s shadow falls on the Earth They only occur during NEW MOON phase Umbra area where the Moon completely covers the Sun Penumbra area where the Moon partially covers the Sun

Lunar Eclipse LUNAR ECLIPSES occur when the Earth comes between the Sun and the Moon and the Earth’s shadow falls on the Moon. Lunar eclipses happen only during a FULL MOON. Lunar eclipses DO NOT happen every month, because the Moon’s orbit is tilted 5˚ in relation to the Earth’s orbit has a reddish tint due to reflected light from Earth, called Earthshine

What causes tides on Earth? Tides are the daily rise and fall of sea level due to the gravitational force of the Moon tugging on the Earth. While the Sun’s gravitational force also pulls on the Earth, the Moon’s tug is more effective, because it is closer to Earth A tidal range is the difference between high tide and low tide at a certain location on Earth. http://homepages.spa.umn.edu/~llrw/a1001_f07/tides.jpg

Kinds of Tides Spring Tides Neap Tides The tidal range is the greatest as the Sun, Moon, and Earth are all aligned at 180o. occur during full and new Moon phases produce higher high tides and lower low tides Neap Tides The tidal range is the smallest as the Sun, Moon, and Earth are all aligned at 90o. occur during first and third quarter Moon phases produce lower high tides and higher low tides