The summer temperatures in the Northern Hemisphere are hitting record highs, with heatwaves sweeping across countries in the region, subjecting residents to one of the hottest summers in history.
.jpg)
Interestingly, around this time, Earth is gearing up to reach its farthest point on its orbit around the Sun for the year. This annual event is called aphelion, derived from the Greek words “apo” (away) and “helios” (Sun), according to the Almanac. This occurrence has prompted many to question: If Earth is at its farthest from the Sun, why is the summer still so unbearably hot?
To address this question, let’s first consider how Earth revolves around the Sun and how our planet’s axial rotation works.
Astronomers consider the average distance between Earth and the Sun to be one astronomical unit (AU), roughly about 93 million miles (150 million km), as defined by the International Astronomical Union (IAU).
However, Earth’s slightly elliptical orbit around the Sun also means that each year, there will be a day when Earth is closest to the Sun (perihelion) and a day when our Blue Planet is farthest from its stellar host (aphelion). In 2023, the perihelion will occur on January 4th, when Earth is 0.98 AU away from the Sun. According to astronomer Fred Espenak, on July 6th this year, during aphelion, Earth will be 1.01 AU away from the Sun.
Looking back in history, the perihelion and aphelion points were first noted by astronomer Johannes Kepler in the 17th century. He also calculated that planets have elliptical orbits around the Sun. He observed that a planet moves fastest when it’s at perihelion and slowest at aphelion. This accounts for the longer duration of summer in the Northern Hemisphere compared to the Southern Hemisphere.
Although the difference between perihelion and aphelion distances might span millions of miles, it has minimal impact on Earth’s temperature. The reason behind Earth’s distinct seasons is its axial tilt of 23.5 degrees. This means that the Sun’s illumination hits different latitudes at varying angles throughout the year.
In July, the Northern Hemisphere tilts toward the Sun, receiving the full radiant light of our star during summer. Meanwhile, the Southern Hemisphere tilts away from the Sun, resulting in shorter days and cooler temperatures there.
Despite aphelion occurring just a few weeks after the June solstice and perihelion near the December solstice, these events are unrelated. The precise timings are caused by the changing eccentricity of Earth’s orbit, according to timeanddate.com, with perihelion and aphelion days shifting by a day every 58 years from the 13th century. Reference: Live Science