Winter solstice - First day of winter
Dec 21, 2019
Winter solstice! First day of winter in the United States. The sun's arc is at its fartherest point south, overhead at the Tropic of Capricorn, which runs through Australia.
The sun's arc never gets overhead in the U.S. because we are too far north. It is overhead twice a year at the equator.
Earth orbits the sun 67,000 mile per hour, and its orbit is 585 million miles long. As Earth orbits the sun, its axis always points in the same direction.
Earth's orbit is an ellipse. The Northern Hemisphere has winter when Earth is closest to the sun. The Southern Hemisphere has winter when Earth is fartherest from the sun, which explains the ice cap at the South Pole.
The sun's arc does not drift north and south. The earth's tilt makes the sun appear to drift north and south during the course of a year. On one side of the orbit, the Northern Hemisphere tilts away from the sun. On the other side, it tilts toward the sun. Midway between the extremes, the sun's rays hit the earth broadside, causing spring and fall. The earth's tilt makes the sun appear to move north and south. Everything on Earth comes from the sun. The earth itself formed from stuff left over when the sun formed.
The 5 major latitude circles are the Arctic Circle. Tropic of Cancer. Equator. Tropic of Capricorn & Antarctic Circle.