The Sun continually produces 380 billion billion megawatts (3.826 × 1026 W) and it for billions of years. For that it consumes 4 million tons of hydrogen per second. This loss of mass is converted into energy, 564 million tons of hydrogen are converted into 560 million tons of helium. The Sun produces its energy through nuclear fusion, due to the pressure and temperature prevailing in his big heart. This pressure and this temperature forcing electrons to break away and travel atoms released from atomic nuclei. Therefore the material no longer behaves like a gas but as a plasma. The nuclei of hydrogen powered against each other by the enormous pressure, will be transformed into helium nuclei. This fusion process generates a core mass slightly smaller and this difference is released as energy.

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. To send us this photon must traverse the various layers of the Sun. The transit time of a photon of the heart at the surface is between 10 000 and 170 000 years based on collisions.

At first the photon begins to penetrate the radiative zone of 300 000 km thick, the density is so high that the photon has trouble moving it from ever colliding with other particles such as atoms and ionized hydrogen helium.

The increase of the photon is chaotic, it is called by scientists, the photon random walk. The photon is absorbed by atoms and reissued immediately, back and forth is repeated millions of times.

As in so far as it goes up to the Sun's surface, the density of matter decreases, there are fewer collisions and interactions, its advance is much less complicated.

When there is more than 200 000 km from the surface, the photon enters the convective zone and the pace is accelerating, the photon is pushed outward, aided by the bubbling of the material. Captivated by huge columns of gas, then it must not only ten days to reach the Sun's surface.

The photon is finally emerging from gas of the solar atmosphere. Then it takes only 8 minutes to cross the 150 million km that separates our planet yet.