The Earth primarily derives its energy from the Sun in the form of short-wavelength radiation, commonly known as insolation, which stands for “incoming solar radiation”. This insolation is crucial for the Earth’s climate, weather patterns, and essentially all forms of life.

Geoid Shape And Solar Energy Reception

The Earth’s shape is often described as a geoid, which closely resembles a sphere. Due to this shape, the Sun’s rays hit the Earth at varying angles, being most direct at the equator and increasingly oblique towards the poles. Because of these varying angles and the spherical shape, only a minuscule fraction of the Sun’s total energy is intercepted by the Earth. On average, the Earth receives approximately 1.94 calories per square centimetre per minute at the top of its atmosphere.

Aphelion And Perihelion: Earth-Sun Distance

The Earth’s distance from the Sun is not constant throughout the year due to its elliptical orbit. When the Earth is farthest from the Sun, at about 152 million kilometres, the position is called ‘aphelion’, which occurs around July 4th. Conversely, when Earth is closest to the Sun, at approximately 147 million kilometres, this position is known as ‘perihelion’, happening around January 3rd.

Interestingly, the Earth receives slightly more insolation during perihelion than during aphelion. However, this difference in solar energy is relatively minor and is largely overshadowed by other climatic factors.

Why The Variation Is Negligible

While one might think that this variation in distance would create a noticeable change in climate or weather, it generally does not. The effect of this small variation in solar output is largely neutralised by other factors, including: