Venus shines brightly in the distance in this picture taken on the International Space Station. (NASA/JAXA)

Earth’s orbit around the sun cycles between nearly circular to slightly elliptical.  This occurs on 405,000 year cycles and is due to the complex interplay of the gravitational pull of bodies in the Solar System on earth, but mainly due to Jupiter and Venus. Jupiter affects our orbit because it is so large and Venus because it is so close (162 million miles away).

This 405,000 year orbital cycle has long been theorized but evidence of the cycle was recently published in the Proceedings of the National Academy of Sciences. In the study the scientists examined 1,500 feet of a rock core sample in Arizona and confirmed ancient lakes drying up and refilling over 405,000 year periods. The lakes dried up and refilled because the shape of Earth’s orbit affects climate because a more elliptical orbit causes larger extremes of temperature over the course of seasons. The rock core sample allowed the scientists to study 215 million years.

A lead author of the study explained the significance of the study: “Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way . . . climate cycles are directly related to how the Earth orbits the sun and slight variations in sunlight reaching Earth lead to climate and ecological changes.”

So, where are we in the cycle now? The study authors think we are near the most circular part of the orbit and changes in orbit are not perceptible in terms of affecting climate over the course of our lifetimes. “It’s pretty far down on the list of so many other things that can affect climate on times scales that matter to us.”