The earth is about to reach the maximum distance point from the sun in its orbit: in technical terms, theaphelionfrom the Greek apo- (“Far”) e Helios (“Sun”). In particular, the 3 July 2025 precisely at hours 21:54 Italian our planet will find itself a 152.087.738 km From the sun, that is 4.94 million km more than perijiums, that is, the point of the terrestrial orbit closest to the sun, which this year fell on January 4th.
But a second: but How is it possible that we are more far from the sun in the middle of the summerwhen is it so hot? First of all, there is a consideration: it is hot in the northern hemisphere, while in the southern one it is now winter. In addition, given in hand the effect of the greatest distance is in fact negligible compared to that ofinclination with which the sun’s rays affect our hemisphere.
When the earth reaches the aphelium and what it means
As we said above, the earth reaches the aphelium in a precise moment, which generally falls in the first days of July. This year the earth will be in Ahilio at 21:54 Italian of July 3. The exact distance from the sun varies slightly from year to year depending on the arrangement of the other planets of the Solar System: their gravitational attraction, albeit small, can in fact slightly deform the terrestrial orbit. However, it is a very small effect (a few thousand km of difference between one year and the other).
One question at this point could be: but why is the earth always at the same distance from the sun? Often we imagine the orbits of the planets as perfectly circular, and in many cases (including that of the earth) the circular form is a very good approximation, but technically The orbits are ellipticalas established by Kepler’s second law. The same law also states that the sun is not located in the exact center of the Ellisse, but slightly split in one of the two points that are called in technical jargon fires of the ellipse. The fact that the orbit of the Earth is slightly “crushed” and that the sun is not exactly in the center explain the difference in distance that it is recorded between Perdie and Afelio.
Because in the north hemisphere it is summer when the sun is further away
At this point we have to face the question of the title: why is it hottest (in the northern hemisphere) just when we are more distant from the sun? If I’m further away from a fire I feel less hot, no longer hot. How do we reconcile the two?
The reason is the same for which we have the seasons, that is The inclination of the earth’s axis. But let’s start from the distance from the sun. As we have seen, between the Afelry and Perielio “dances” a difference of about 5 million km, which are certainly many compared to our stairs, but in convenient at the average land-sail distance, which is of 149,600,000 kmis just a 3.5%. The amount of energy coming from the sun certainly depends on the distance, but calculating a difference of 3.5% in the distance it produces one difference in energy received by approximately 6.5%. Which would not be negligible in an absolute sense, but vanishes compared to the difference due to the fact that during the summer the sun’s rays reach the ground much more inclined than the ground, bringing us much more energy per square meter.
This is in turn due to the fact that the terrestrial axis is inclined to 23 ° 27 ‘ compared to the orbital plane. Between the day of the summer solstice and the winter, therefore, the difference in inclination of the sun’s rays is approximately 47thcausing enormous variation in terms of irradiation. In our latitudes we are talking about a difference in 250% approx: in other words, in summer the solar energy per square meter is up to 2 and a half times greater compared to the one we receive in winter. An effect, this, decidedly above the much more modest -6.5% due to the different distance from the sun.
