The Earth has two constant motions: rotation and revolution. The Earth's rotation The Earth rotates on its own axis. It takes 24 hours (one day) to complete one rotation . The Earth is a sphere. This means the Sun's rays do not illuminate all of Earth at the same time. When one side of Earth is illuminated , the opposite side is in darkness. Ever y 24 hours there is a succession of day and night. The lengths of the days and nights var y throughout the year. (5) This succession regulates the temperature of the planet: during the day, the illuminated part of the Earth heats up; during the night, the part of the Earth that does not receive sunlight cools down . The Earth's revolution The Earth also moves around the Sun in an elliptical orbit. It takes 365 days and almost 6 hours to complete one orbit of the Sun (one year). (6) However, years usually have just 365 days. Therefore, every four years a day is added to compensate for the extra hours (6 hours every year 3 4 5 24 hours, or one day). This leads to years that have 366 days, which are called leap years. The Earth is tilted. As a result, the Sun's rays strike the two hemispheres differently throughout the year. This is what causes the seasons. 2. The Earth is constantly moving 5. The Earth's rotation COMMUNICATION Get creative. Use a torch and some spheres to explain the rotation and revolution of the Earth. DIBUJO 191 x 104 mm 6. The Earth's revolution summer solstice spring equinox elliptical orbit autumn equinox winter solstice summer summer winter winter spring spring autumn autumn SUN day North Pole night solar rays South Pole axis of rotation the Earth's tilt: 23º 27' to the Sun 12
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