Celebrations and Orbits
Our planet orbits the Sun as it has for the past several billion years. The Earth's axis of revolution is currently tilted from its orbital plane by about 24 degrees from perpendicular. This causes the seasons, and also the drift throughout the year in the height above the horizon of the Sun's arc across the sky as it appears to move from sunrise to sunset. The winter solstice occurs in the northern hemisphere when this arc is at its lowest, resulting in the shortest day and longest night of the year, and usually occurs on December 21st or 22nd. For the next 6 months, this arc will rise. Earth’s orbit is an ellipse with the closest point to the Sun, perihelion, occurring sometime between January 2nd to the 5th. It is winter because the axial tilt of the northern hemisphere away from the Sun more than compensates for the approximately 6% more solar influx than at aphelion, the farthest point. Note, though, that it is summer in the southern hemisphere at perihelion. Life on Ear