Module 7

• Speed of the Earth's orbit around the sun

  110,000 km/h
• Time it takes for the Earth to complete one orbit around the sun

  365.242199 solar days
• Average distance of the Earth from the sun

  149.6 million km
• Shape of the Earth's orbit around the sun


  Elliptical orbit
• The earth orbits the sun in an elliptical manner
• The Earth's orbit around the Sun is 108,000 km/h
• The earth completes 365.242199 solar days in one orbit
• The Earth's distance from the Sun varies as it orbits
• When the Earth is closest to the Sun, it is at perihelion
• When the Earth is at its farthest distance from the Sun, it is at aphelion
• Aphelion happens around July 4th
• The Philippines is in the Northern Hemisphere, which is tilted toward the Sun during summer
• In June, the Northern Hemisphere receives direct rays from the Sun
• In December, the Southern Hemisphere receives direct rays from the Sun
• Rotation


  The earth spins around an imaginary line that runs through its center, called the axis. Every twenty-four hours, the earth makes one complete spin or rotation.
• Equator


  An imaginary line that divides the earth around the middle into two halves - the Northern hemisphere and the Southern hemisphere.
• Revolution


  The movement of the earth around the sun in a path called an orbit.
• The earth revolves around the sun at a speed of 108,000 kilometers per hour.
• The earth completes one orbit around the sun every 365 days, 6 hours and 8 minutes (approximately 365 1/4 days or one year).
• The remaining one-fourth day is added to the calendar after every four years, creating a leap year with 366 days.
• Earth's axis


  The imaginary line that the earth rotates around, tilted at 23.5 degrees from the vertical.
• The orientation of the Earth's axis remains fixed throughout the seasons, pointing directly toward Polaris, the North Star.
• The Earth's axis tilt

  Causes the Northern Hemisphere to be tilted away from the Sun in December and towards the Sun in June.
• During the spring and fall equinoxes, the subsolar point is over the equator with a sun angle of 90 degrees at solar noon, and all latitudes (except the extreme poles) receive roughly the same length of daylight and darkness.
• The Sun's altitude


  Declines with latitude as one travels away from the Equator, decreasing by the same amount for each degree of latitude.
• During the summer solstice, the subsolar point moves to the Tropic of Cancer (23.5° N) as the Northern half of the Earth is angled towards the Sun.
• During the winter solstice, the subsolar point is located at the Tropic of Capricorn (23.5° S) when the South Pole is tilted 23.5° towards the Sun.
• Perihelion


  When the Earth is closest to the Sun, around January 3rd each year, at a distance of about 147,098,074 km.
• Aphelion


  When the Earth is farthest from the Sun, around July 4th, at a distance of about 152,097,701 km.
• The average distance of the Earth from the Sun is about 149.6 million km, referred to as one astronomical unit (AU).
• The small difference between the aphelion and perihelion (less than 5 million km) is not enough to affect the seasons on Earth.
• When the earth is tilted away from the sun we have night
• The tilting of the earth changes the angle that the sun strikes the earth in different land areas
• When it is summer in the southern hemisphere, the northern hemisphere is tilted away from the sun
• The sun's height is at the maximum when it is directly overhead at solar noon
• Solstices


  The point in the orbit of maximum axial tilt toward or away from the sun
• In June, the direct rays from the sun hit mostly in the Northern Hemisphere
• In December, the direct rays from the sun hit mostly in the Southern Hemisphere
• Earth's orbit


  The path of the Earth around the Sun
• It takes the Earth 365 days to complete one revolution around the sun