Explanation:

Perihelion is the point in the Earth's orbit where it is closest to the sun. It is the opposite of aphelion, which is the point in the Earth's orbit where it is farthest from the sun. The Earth's orbit is not a perfect circle but rather an ellipse, with the sun at one of the foci of the ellipse. This means that the distance between the Earth and the sun varies throughout the year.

The Earth reaches its perihelion in January. This means that the Earth is closest to the sun in January and farthest from the sun in July. The exact date of perihelion varies from year to year, but it is usually around January 3rd or 4th.

There are a few reasons why the Earth's perihelion occurs in January. One reason is that the Earth's orbit is slightly tilted with respect to the plane of the solar system. This tilt, known as the obliquity of the ecliptic, causes the seasons on Earth. When the Earth is closest to the sun, it is winter in the Northern Hemisphere and summer in the Southern Hemisphere. This is because the tilt of the Earth's axis causes the sun's rays to hit the Earth at a more oblique angle in the winter, which results in less direct sunlight and cooler temperatures.

Another reason why the Earth's perihelion occurs in January has to do with the gravitational pull of other planets in the solar system. The positions of the other planets can influence the shape and orientation of the Earth's orbit, causing it to shift slightly from year to year. This can affect the timing of perihelion.

In summary, the Earth reaches its perihelion in January because of the tilt of its axis and the gravitational influence of other planets in the solar system.