Over 10s to 100s of thousands of years, these small changes in the position of the Earth in relationship to the Sun can change the amount of solar radiation, also known as insolation, received by different parts of the Earth. Small changes in Earth’s spin, tilt, and orbit over these long periods of time can change the amount of sunlight received (and therefore absorbed and re-radiated) by different parts of the Earth. Additionally, how much Earth’s axis is tilted towards or away from the Sun changes through time, over approximately 41,000 year cycles. Over 19,000 – 24,000 years, the direction of Earth’s tilt shifts (spins). Over approximately 100,000 – 400,000 years, gravitational forces slowly change Earth’s orbit between more circular and elliptical shapes, as indicated by the blue and yellow dashed ovals in the figure to the right. Over long periods of time, the gravitational pull of other members of our solar system slowly change Earth’s spin, tilt, and orbit. As the Earth orbits the Sun, the Earth is pulled by the gravitational forces of the Sun, Moon, and large planets in the solar system, primarily Jupiter and Saturn. Daily changes in light and temperature are caused by the rotation of the Earth, and seasonal changes are caused by the tilt of the Earth.

Animation of earth spinning and seasons