Earth and Moon Mrs. Blackmer

Earth Earth is the third planet from the Sun and the only known planet to have life. From space the Earth is seen as a sphere that is mostly blue because three-fourths of its surface is covered with water. Brown and green continents and white ice-capped poles are also seen from space. It has a diameter of 12,800 kilometers (or 7,900 miles). It has one natural satellite which is the Moon.

Earth (Continued) The entire planet is surrounded by a thin blanket of life-sustaining air called the atmosphere. The atmosphere is made up of about 78% nitrogen, 21% oxygen, and 1% of other gases such as argon, carbon dioxide, water vapor, and other gases. At any given time about half of the Earth is covered with clouds, which are part of the atmosphere, that protect the surface from extreme heat. The clouds also retain, or hold, the heat that is absorbed so that the planet does not become too cold as it rotates (on its axis) away from the sun and begins to experience night. The atmosphere also acts like a shield by preventing the Sun’s deadly ultraviolet rays from getting through.

Earth (Continued) The Earth spins around a tilted axis (it is tilted 23.5 degrees) that passes through the center of the Earth. One complete rotation marks the passing of an entire day and night (23 hours and 56 minutes or 24 hours). The Sun’s rays reach only half of the Earth at any one time (this side in daylight) because light travels in a straight line. The side that the Sun’s rays does not reach experiences night.

Earth (Continued) At the same time that the Earth rotates (or spins) on its axis, it also revolves (or goes around) the Sun. It takes the Earth days and nights (or rotations) to revolve around the sun one complete time. The Earth orbits the sun at a speed of 24 kilometers per second (or 15 miles per second). The orbital path of Earth is the shape of an ellipse.

Earth (Continued) The tilted axis of the Earth and the yearly orbit of the Earth around the Sun cause variations in the amount of heat at different locations on Earth at different times of the year- which causes seasonal changes (or the seasons).

Moon The only natural satellite of the planet Earth is the Moon. It is about one fourth the size of Earth and has no known life, air, food, or liquid water. It does however have frozen water. The moon is 385,000 kilometers (239,000 miles) from Earth. Its diameter is 3,476 kilometers (2,160 miles). It takes a jet about 4 months to travel from Earth to moon and a rocket 3 days. About three fourths of the Moon is covered with mountains and craters formed by crashing meteors. The craters are as large as 1,000 km. (620 mi.) across and as small as dots. The rest of the Moon is smooth and dark (these area are commonly called seas).

Moon The gravity on the Moon is 1/6 of that on Earth. Therefore, the Moon’s gravity is too weak to hold an atmosphere. However, it is close enough to cause ocean tides on Earth. Since there is no atmosphere, water, or air on the Moon, there is also no wind or weather like there is on Earth, which causes everything to remain the same on the surface of the Moon. In fact the original footprints of the astronauts that first explored the Moon’s surface in 1969 are still there today and will remain there for millions of years unless something crashes into them.

Moon It takes the Moon 27.3 days to rotate on its slightly tilted axis (only 1.5 degrees- so small that there are no seasons). One half of the Moon always has the sun’s rays shining on it just like Earth, but its day and night are much longer than Earth’s (about 13.5 Earth days of day and 13.5 Earth days of night). Although the Moon has a day, it does not give off any light. The light that we see at night is the Sun’s light that is reflected off of the moon’s surface. The average temperatures on the Moon are 1,300 °C (2,660 °F) during the day and -1,730 °C (- 2,800 °F) at night.

Moon At the same time that the Moon revolves around that Sun with Earth, it is also revolving around Earth. The orbital speed of the Moon around Earth is 1 kilometer per second (6 miles per second). The Moon revolves at the same rate it rotates, so the same side always faces Earth. Humans did not know what was on the far side of the Moon until 1959 when a Russian spacecraft brought back pictures.

Moon As the moon orbits Earth, an observer on Earth can see that the Moon seems to change shape. It seems to change from a crescent to a circle and back again. The shape looks different from one day to the next because different amounts of the moon's lighted side become visible to the observer. As the moon changes from new moon to full moon, and more and more of it becomes visible, it is said to be waxing. As it changes from full moon to new moon, and less and less of it can be seen, it is waning. When the moon appears smaller than a quarter moon, it is called crescent. When it looks larger than a quarter moon, but is not yet a full moon, it is called gibbous.

Moon The Moon revolving around Earth also causes eclipses. Eclipses occur when Earth, the sun, and the moon are in a straight line, or nearly so. A lunar eclipse occurs when Earth gets directly -- or almost directly -- between the sun and the moon, and Earth's shadow falls on the moon. A lunar eclipse can occur only during a full moon. A solar eclipse occurs when the moon gets directly -- or almost directly -- between the sun and Earth, and the moon's shadow falls on Earth. A solar eclipse can occur only during a new moon. A lunar eclipse below:A solar eclipse below: