Monday, June 21, 2021

Mechanism of a journey of photons from Sun to earth

A photon of light takes only eight minutes to get to the Earth from the surface of the Sun. But it can take 100,000 years from the core of the Sun to get to the surface, where it bursts out and flies at the speed of light. The energy produced by nuclear fusion is conveyed from the heart of the Sun by light particles and heat, called photons. When merging two protons in a nucleus of deuterium to create a helium nucleus, photons are released. This particle, created in the solar core, transmits the light beam to Earth.

The outer layers are the Photosphere, the Chromosphere, the Transition Region, and the Corona. The temperature in the photosphere varies between about 6500 K at the bottom and 4000 K at the top (11,000 and 6700 degrees F, 6200, and 3700 degrees C). Since the Sun has no solid surface, any radiation that hits the Sun is scattered and absorbed until it is completely lost. Wien's displacement law states that the black-body radiation curve for different temperatures will peak at different wavelengths that are inversely proportional to the temperature. So, photons ranging from different layers of the sun has a different wavelength. The powerful processes happening inside the Sun are so robust that it emits every color of light imaginable. Together, these colors form a pure white light, which is precisely what you'd see from space.

The photons approach the Earth's atmosphere at the speed of light, but once they come in contact with the Earth's atmosphere they begin to interact with gas molecules. Gas molecules absorb the photons and then instantly re-emit them. Rayleigh scattering,( named after the nineteenth-century British physicist Lord Rayleigh,) is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. Rayleigh scattering of sunlight in Earth's atmosphere causes diffuse sky radiation, which is the reason for the blue color of the daytime and twilight sky, as well as the yellowish to the reddish hue of the low Sun. 

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