Ch. 1Earth, Moon, and Sun This amazing Earthrise above the moons horizon was seen by astronaut Michael Collins in the Apollo 11 moon orbiter Columbia.
ObjectivesIdentify the effects of Earth’srotation and revolution.Explain the causes of theseasons on Earth.
Section 1, Earth in Space Why Does Earth Have Day and Night?
Introduction Egyptian farmers planted their crops after the floods every year. They noticed that the star Sirius became visible before the floods. That’s when they could start predicting the floods. The Egyptians were the first people to study the stars.
Days and Years Astronomy is the study of the moon, stars, and other objects in space.
Rotation Axis - the imaginary line that passes through Earth’s center and the North and South poles. Rotation - the spinning of Earth on its axis. A point on the equator rotates at about 1,600 km per hour.
RotationEarth’s rotation on its axiscauses day and night.Earth rotates eastward.It takes 24 hours to rotateonce on its axis. This is calleda day.
RevolutionEarth also travels around thesun.Revolution - the movement ofone object around anotherobject.Earth’s orbit is an oval shape.
CalendarsThe Egyptians counted the number ofdays between Sirius stars which wasabout 365.Earth’s orbit around the sun is about365 1/4 days.Four years of 365 1/4 days each canbe approx. by taking 3 years of 365days and a fourth year of 366 days.This is known as leap year.On a leap year, one extra day inFebruary is added for 29 days.
CalendarsDividing the year into smaller parts(months) was difficult.Early people used the moon cyclewhich is 29 1/2 days but this onlyadded up to 354.The Egyptians had a plan to have 12months of 30 days and 5 extra days.The Romans borrowed the calendarand devised the one that we havetoday with 11 months of 30 to 31days and February with 28 or 29days.
Seasons on Earth Most places have four seasons: winter, spring, summer, and autumn.
Earth’s Tilted Axis Earth has seasons because its axis is tilted as it moves around the sun.
Earth in June The north end of Earth’s axis is tilted toward the sun. It is summer in the Northern Hemisphere and winter in the Southern Hemisphere.
Earth in December The south end of Earth’s axis is tilted toward the sun. It is summer in the Southern Hemisphere and winter in the Northern Hemisphere.
Both in June and December Summer solstice - longest day of the year (June 21). Winter solstice - shortest day of the year (December 21). Both of these are in the Northern Hemisphere and the opposite in the Southern Hemisphere.
Earth in March & September Neither hemisphere is tilted toward or away from the sun. So the days and nights are in an equinox which is equal.
Earth in March and September Vernal equinox, or spring equinox occurs around March 21 and is the first day of spring. Autumnal equinox, or fall equinox occurs around September 23 and is the first day of fall.
Solstices andEquinoxes Solstices occur when the sun reaches its greatest distance north or south of the equator twice each year, each of these days, when the sun is the farthest north or south of the equator. Equinoxes occur twice a year, when the noon sun is directly overhead at the equator.
Plants and Animals Plants and animals are effected by the amount of day light hours. In the spring and summer, plants grow, and animals feed on the plants. Insects and animals get more food. In the winter, animals go dormant and birds travel to warmer climates to find food.
Reasons for the Seasons Lab Books, Styrofoam balls and flashlights.
Gravity and Motion Gravity gives the Universe its structure It is a universal force that causes all objects to pull on all other objects everywhere It holds objects together It is responsible for holding the Earth in its orbit around the Sun.
Inertia Galileo established the idea of inertia A body at rest tends to remain at rest A body in motion tends to remain in motion Through experiments with inclined planes, Galileo demonstrated the idea of inertia and the importance forces (friction) This concept was incorporated in Newton’s First Law of Motion :An object at rest will remain at rest, an object in motionwill remain in motion in a straight line, unless acted on
Phases of the Moon Phases of the moon are seen by the reflection of the sun on the moon’s surface. The different shapes of the moon you see from Earth are called phases. The moon goes through its whole set of phases each time it revolves around the Earth, about once a month.
What Causes Phases? Phases are caused by changes in the relative positions of the moon, Earth, and the sun. The phase of the moon you see depends on how much of the side of the moon faces Earth.
EclipsesWhen the moon’s shadow hitsEarth or Earth’s shadow hitsthe moon, an eclipse occurs.Two types of eclipses:solar and lunar
Solar EclipsesDuring a new moon, most of thetime the moon is a little above orbelow the sun in the sky.A solar eclipse occurs when themoon passes between Earth andthe sun, blocking the sunlight fromreaching Earth.It is really a new moon that blocksyour view of the sun.
Total Lunar Eclipses A lunar eclipse occurs at a full moon when Earth is between the moon and the sun. Earth blocks sunlight from reaching the moon.
Total Lunar Eclipse When the moon is in Earth’s umbra, you see a total lunar eclipse. You are more likely to see a total lunar eclipse than a total solar eclipse.
Partial Lunar Eclipses Occurs when the moon passes partly into the umbra of Earth’s shadow. The edge of the shadow appears blurry and you can watch it pass across the moon for up to two or three hours.
TidesTwo high tides and two low tides occurdaily, over 24 hours.The water rises for about six hours,then falls for about six hours, in aregular cycles.Tides are caused mainly by differencesin how much the moon ‘s gravity pullson different parts of earth.The Tide cycle is representing the twopoints of high tides due to the strengthand weakness of the moon’s gravity onthe earth as a whole at those pointscausing the tides keeping betweenthem the other two low tides.
Gravity and Tides Low tides occur The moon’s gravity between the two causes high tide on high tides. the side closest to the moon.The force of themoon’s gravity pullsEarth toward themoon, leaving thewater behind
Spring Tides and Neap Tides: Spring Tides: the combined gravity forces of the sun and moon produce a tide of the greatest difference between consecutive low and high tides, called spring tide. It happens twice a month, at new moon and at full moon.
Neap Tides During the moon’s first quarter and third quarters, the line between earth and sun is perpendicular on the line between earth and moon, so the sun’s pull at right angles to the moon’s pull produces the Neap Tides. It occurs twice a month.
Section 4, Earth’s Moon Maria In 1609, The Italian Scientist Galileo Galileo succeeded to see that the moon has an irregular surface with a variety of remarkable features that are called craters (pits), by the help of a telescope that built to Highlands observe distant objects.
The Moon’s SurfaceFeatures on the moon’s surface include Maria, craters, and highlands. Maria; they are dark, flat areas actually hundred rock formed from lava flows from 3 or 4 billion years ago. Craters; they were caused by the impacts of meteoroids, chunks of rock or dust from space, also on Earth, some craters were disappeared due to water, wind and other forces for billions of year. Highlands; They looked as light-coloured features as the peaks of the lunar highlands and the rims of craters cast shadows, which Galileo could see by his Telescope.
Characteristics of the Moon The moon is dry and airless, compared to Earth, the moon is small and has large variations in its surface temperature.
Size and Density of themoon Diameter; is 3, 476 km. = ¼ Earth’s diameter. 1/8 as much as mass as Earth. Its average density = density of Earth’s outer layers. Its core is less denser than Earth’s core.
Temperature and Atmosphere Temperature on the moon vary so much because it has no atmosphere. It ranges from torrid 130 °C in direct sunlight to a frigid -180 °C at night. The moon surface gravity is so weak that gases can easily escape into space.
WaterThere is evidence that theremay be large patches of icenear the moon’s poles.The moon has no liquid water.Some areas are shielded fromsunlight by crater walls.
The Origin of the Moon The moon is formed by “ Collision- ring theory” that says planet-sized objects collided with Earth to form the moon. i.e. materials from the object and Earth’s outer layers was ejected into orbit around Earth, where it is formed a ring. Gravity caused these materials to combine to form the moon.