We are entering more and more into the summer season. After the summer solstice, last June 20, we are now at the dawn of July, and summer is in full swing. However, in this year 2024, the weather is rather uncertain in France, with thunderstorms and cool temperatures again forecast for the next few days.
Yet, just like in the northern hemisphere we are in summer, with long days and warmer temperatures, Earth is about to reach its furthest point from the Sun, known as aphelion, touching a maximum distance of approximately 152,000,000 kilometers from the central star of our solar system.
In 2024, Aphelion will be reached on July 5, at 5:07 UTC. This phenomenon, which occurs every year, fascinates and raises many questions. Indeed, one may wonder how it is possible that at the very beginning of summer, the Earth is furthest from the Sun. In this article, we will discover a little history.
The Earth’s orbit is elliptical
The Earth revolves around the Sun in a revolutionary motion that lasts approximately 365 days and 6 hours. (this is why there are leap years every four years), traveling in an elliptical orbit. The hypothesis that the orbits of the planets are elliptical was formulated by the German astronomer Kepler, a contemporary of Galileo.
It was the astronomer Kepler who hypothesized that the orbits of the planets around the Sun had an elliptical shape, with the Sun occupying one of the foci of the ellipse.
The fact that the Earth’s orbit around the Sun is elliptical and not circular has obvious consequences: there is a time of year when the Earth is furthest from the Sun, and another when it is closest.
Aphelion and perihelion
The point of maximum proximity between the Earth and the Sun is called perihelion. and is reached at the beginning of January, when our planet reaches the minimum distance of 147,000,000 kilometers from the Sun.
The point of maximum distance is rather called aphelion, a term introduced by the astronomer Kepler, who used the Greek “apo” meaning “far from”, and “helios” meaning “sun”. This point is reached at the beginning of July, and the distance between the Earth and the Sun at this precise moment is 152 million kilometers.
Further from the sun in the middle of summer? Distance has no influence on the change of seasons.
This may seem strange, but in reality the succession of seasons is not linked to the distance of the Earth from the Sun. The difference between 147 and 152 million kilometers is too small to have an influence on the temperature of the planet and the succession of seasons, and it is imperceptible to us humans.
The difference between 147 and 152 million kilometers is too small to have an influence on the planet’s temperature and the succession of seasons, and it is imperceptible to us humans.
Indeed, at the beginning of July, when aphelion is reached, we are in the middle of summer in the northern hemisphere but in the southern hemisphere, remember, it is winter. The succession of seasons is not linked to the distance between the Earth and the Sun, but to the particular inclination of our planet in relation to the sun’s rays.
Our planet’s elliptical orbit around the Sun is inclined about 23° from the perpendicular to the plane of the orbit. During the year, the Earth’s particular tilt causes the sun’s rays to reach different regions of the planet differently.
When it is summer in the Northern Hemisphere, the sun’s rays reach the Northern Hemisphere at a lower angle and for a longer time, while the opposite occurs in the Southern Hemisphere. This determines the alternation of the seasons and the occurrence of important astronomical moments such as the equinoxes and solstices.
It is therefore not the Earth-Sun distance which determines the hot or cold periods, and in general the seasons, but the difference in the inclination of the Earth’s axis in its movement of revolution.
