The earth will be on the point furthest from its orbit on Thursday July 3 at 9:54 p.m. How to explain when it is so hot?
While France and more generally Western Europe are going through a strong heat wave period, with temperatures sometimes exceeding 40 ° C, the earth paradoxically reaches its point furthest from the sun. This Thursday, July 3, at 9:54 p.m. and 43 seconds, Paris time (7:54 p.m. UTC), our planet will be at 152,087,738 kilometers from our star, according to the time-space laboratory of the Paris Observatory, a record distance for the year.
This astronomical phenomenon, called Aphélie, returns every year. The term comes from Greek «apo» (far) and «helios» (Sun), and designates the moment when the earth is at the end of its orbit, the most distant from the sun. This orbit is not perfectly circular, but slightly elliptical, which causes a variation in the distance between the earth and the sun during the year.
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No link with the seasons
Unlike the aphelia, perihelion generally occurs at the start of the year. Indeed, on January 4, the earth was only 147,103,686 kilometers of the sun. The difference between these two positions reaches almost 5 million kilometers, or around 3 % of the average distance. The difference in flow between perihelion and aphelia is therefore approximately 9%.
It may seem a lot, but it is actually very little and has no direct link with the temperatures we know. The seasons are determined by the inclination of the earth’s axis, about 23 ° C compared to the ecliptic, and not by proximity to the sun. When the northern hemisphere is tilted towards the sun, the rays are more vertical (the sun is higher in the sky) and the solar flow more concentrated. The day is also longer, the hemisphere stores more energy, almost twice and a half more than the other (about 133% in addition): it is summer. At the same time, the southern hemisphere is in winter. In six months, the roles will be reversed and the earth will be closest to the sun. Which shows that it is not the distance from the sun that counts.
Thus, despite the heat wave which currently strikes a part of the globe, the earth quietly continues its race around the sun, according to the immutable laws of celestial mechanics.
