The average distance between the Earth and the Sun, which astronomers call an astronomical unit, is defined as 149,597,870.7 kilometers. So, this time we were slightly more than 1.5% farther from the sun than average. If you are curious, the last perigee occurred on January 4, 2023 (14 January 1401), and the center of the Earth was 147,098,924 km from the center of the Sun; That is, it was about 1.5 percent closer than the average.
The small effect of these orbital deviations explains why the Earth’s path around the Sun is so similar to a perfect circle. And these effects correspond to only about a 3% change in the apparent diameter of the Sun in the Earth’s sky; Far less than the human eye can detect, unless you’ve lost your vision by improperly staring at the sun without protection.
The most amazing thing about this cycle is when the effect of this interval is seen on the calendar. The perigee occurs every year in January or December, while the orbital apogee is in July or July. This means that in the Northern Hemisphere, we are closer to the Sun in winter and much further away in summer. Exactly the opposite of what is expected.
The point here is that the change of season does not depend on the distance of the earth from the sun. The real reason for the change of seasons is that the Earth’s axis of rotation is tilted about 23 degrees with respect to the plane of the Earth’s orbit; In this way, during a year, the Earth’s North Pole moves towards the Sun or away from it.
The North Pole is most tilted away from the Sun during the summer solstice in late June, or the day of the year when the Sun is at its highest point and spends the most time above the horizon in the Northern Hemisphere. Summer heat in the Northern Hemisphere comes from the season’s longer, brighter days, which allow the sun more exposure and more time to warm the Earth.
During the winter solstice in December, the northern axis of the earth is at the greatest deviation from the sun, the sun is lower in the northern sky and the day is shorter in the northern hemisphere; As a result, that part of the earth is covered by winter cold. Also, the Earth’s axial tilt explains why seasonal temperature rarely changes around the equator; This is because the position of the sun’s movement from above the earth is mild in the middle latitudes.