Why is the Earth so hot even though it is farthest from the Sun?

Tomorrow the Earth will be at its farthest from the Sun, but the distance will not affect the hot temperatures in the Northern Hemisphere.

Earth will be at its farthest point from the Sun tomorrow. Photo: NASA

Temperatures may be high in the Northern Hemisphere, but on July 6, Earth will be at its farthest point from the sun this year. That's called the apogee, a term that comes from the Greek words "apo" (far) and "helios" (sun). The way Earth spins as it orbits the sun may explain why the planet experiences scorching heat when it's furthest from the sun, according to Live Science .

Astronomers call the average distance between Earth and the Sun an astronomical unit (AU), which is approximately 150 million kilometers, as defined by the International Astronomical Union (IAU). However, Earth's elliptical orbit around the Sun means that each year, there is one day when Earth is closest to the Sun (perihelion) and one day when it is farthest from the Sun (apohelion). In 2023, perihelion falls on January 4, when Earth is 0.98 AU (146,605,913 km) from the Sun. On July 6, at perihelion, Earth will be 1.01 AU (151,093,849 km) from the Sun.

Perihelion and apogee were first noticed in the 17th century by astronomer Johannes Kepler, who calculated that planets move in elliptical orbits around the Sun. He found that a planet moves fastest at perihelion and slowest at apogee, according to NASA. That makes summer in the Northern Hemisphere a few days longer than summer in the Southern Hemisphere.

Although the difference between perihelion and aphelion can be several million kilometers, this difference has little effect on Earth's temperature. In July, the Northern Hemisphere is tilted toward the Sun, so it receives full sunlight in the summer, making the days longer and hotter. Meanwhile, the Southern Hemisphere is tilted away from the Sun, so the days are shorter and cooler.

Although Earth reaches perihelion just a few weeks after the June solstice and perihelion close to the December solstice, the two events are unrelated. The exact timing depends on fluctuations in Earth’s orbit. Since the 13th century, the timing of perihelion and perihelion has shifted by a day every 58 years.

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