This weekend we get a close up view of a full moon, called a Super moon. It happens because the Earth and Moon are as close together as they will be for a while.
The moon and the planets have elliptical orbits. We all know it, but we still think of them as being circular. The notion that the moon will appear brighter and bigger, because it is closer to us seems odd. We all get the benefit of it this weekend with a really cool full moon.
Ever think about why February only has 28 days? Earth’s elliptical orbit. Winter and summer are different lengths. Summer is 3 days longer than Winter in the Northern Hemisphere. The Earth is closest to the sun in January and furthest away in July. It takes longer to go around the big part of the ellipse.
In about 11,000 years the opposite will be true. The seasons will shift, summer and winter will change places as the earth wobbles as it orbits. There will also be more variation between winter and summer than today as the elliptical orbit gets bigger. And the sun will be a bit lower in the sky in summer and a bit higher in winter as the amount of axial tilt is reduced.
The Earth’s orbit changes because of all the other orbiting bodies in our Solar System. It’s gravity doing its job. The Earth changes in three ways, the size of the ellipse, the amount of the axial tilt, and the wobble of the planet.
These orbital cycles are believed to change climate as they change. Some scientists think they are a dominant factor in our ice age world. As the orbit changes shape, it changes the amount of solar energy that reaches the Earth.
I could try to explain how it works, but others do it better. If you are interested, the National Academy of Sciences has a great group of diagrams that explain the cycles. In the mean time enjoy the full moon in the warmth of a peak period in our ice age cycle.