What has the earths axis got to do with night and day?

Answer 1

First, envision the plane formed by the earth's orbit, with the sun at it's centre. If the axis of the earth were perpendicular to that plane (that is, at a 90 degree or right angle), then the length of day in places like New York (in the Northern Hemisphere) or Sao Paolo (in the Southern Hemisphere) would be constant year round. And, the equator would lie in the same plane as the earth's orbit. But, in reality, the axis of the earth is not at a 90 degree angle and the plane in which the equator lies is not the same as the earth's orbit. This has the effect that, as the earth orbits the sun, the length of day changes dramatically throughout the year in places like New York and Sao Paolo. While it is winter and days are short in New York, it is summer and days are longer in Sao Paolo. So, the fact that the earth's axis is not perpendicular to the earth's orbital plane is related to changes in day length and the presence of different seasons of weather.