Milankovitch cycles

• Milutin Milankovitch proposed three additional motions (now called as Milankovitch cycles)
• • Precession - the Earth's axis is tilted by 23.5 degrees and it spins on another axis. It takes 25,700 years to complete a cycle. In 3000 BC, the axis is pointed towards Thuban in Draco. In 1400 a. d. ,Vega in Lyra will be the new North Star.
• • Variation in axial obliquity - the axis constantly changes it's tilt. Now, the axis is tilted at 23.5 degrees. It will come to a more upright angle at 22.1 degrees and will tip to 24.5 this cycle will take 41,000 years to complete.
• Variation of the orbital Eccentricity - The orbit of the earth around the sun varies between circular and elliptical. Currently, the earth's orbit is almost circular, its perihelion is equal to its aphelion. This takes approximately 100,000 years to complete.