The distance between the Earth and the Sun changes due to the elliptical shape of the Earth's orbit. The Earth's orbit is not a perfect circle, but rather an ellipse with the Sun at one of the two foci. This means that the distance between the Earth and the Sun varies throughout the year, with the closest point being perihelion and the farthest point being aphelion.
The date of perihelion is not fixed forever. Due to a slow, gradual process called the precession of the equinoxes (a 26,000-year wobble of Earth’s axis), the timing of perihelion shifts over millennia. Approximately 10,000 years from now, perihelion will occur during the Northern Hemisphere’s summer, making summers even hotter and winters even colder than they are today. when is the sun closest to the earth