• What is sunlight?
• Origin of sunlight
• Composition of sunlight
• Importance of sunlight
• Sunlight on plants
• Benefits of sunlight
• Risks of sunlight

We explain what sunlight is, what is its origin and composition. Also, why it is so important, its risks and benefits.

Earth receives about 4,000 hours of sunlight annually in its equatorial regions.

What is sunlight?

We call sunlight the full spectrum of electromagnetic radiation coming from the central star of our planet. Solar system, the Sun. Its presence in the sky determines the difference between day and night, and constitutes a vital part of our conception of the world at every level.

The sun is the source of light Y heat most important and constant that we know, thanks to which the planet Earth has the ideal conditions for life. The electromagnetic radiation that this star emits penetrates the atmosphere and they reach an intensity of 93 lumens of illumination per watt of electromagnetic power, along its three light spectra: infrared, visible and ultraviolet.

The way sunlight reaches the land surface depends largely on the orbital position of the planet, its inclination and rotatory motion, as well as the percentage of Energy which is dissipated by the atmosphere, especially by the ozone layer.

Our planet receives around 4,000 hours of sunlight per year in its equatorial regions, and it is estimated that without these natural filters, its intensity would be such that our planet would be much hotter and much more desert, similar to our neighbor, Mars.

Origin of sunlight

The sun produces different levels of heat and electromagnetic radiation.

Sunlight is the product of nuclear fusion reactions that occur in the heart of the Sun, in which its abundant hydrogen is transformed into helium and other heavier elements, by the action of the immense gravity of the star (owning more than 99% of the mass Of the solar system).

This eternal atomic bomb in space produces different levels of heat and electromagnetic radiation, which in its outermost layer, the photosphere, reaches a thermal equilibrium and the highest temperatures, as well as multiple electromagnetic waves, whose visible spectrum is what we call sunlight or natural light.

Composition of sunlight

If sunlight enters a prism it will break down into its various wavelengths.

Sunlight consists of the propagation of Energy And not from matter through space, that is, in a form of radiation that travels through five different regions of length from wave, What are they:

• Ultraviolet C (UVC) light. Light at its highest frequency, in a range between 100 and 280 nm. Most of it is absorbed by the atmosphere, fortunately, as it has an intense impact on life and the DNA. Its name comes from the fact that it is in a range much higher than that of violet light, the highest that the human eye can capture, that is, it is an invisible type of light.
• Ultraviolet B (UVB) light. Ranging between 280 and 315 nm, it has a strong impact on the atmosphere, where it triggers most of its photochemical reactions, such as the production of the ozone layer. In this way, it also reaches the earth's surface in very low quantities.
• Ultraviolet Light A (UVA). With a range between 315 and 400 nm, it is the form of high-frequency radiation that most strikes the earth's surface, without being visible to the human eye. To her we owe the tanning of our skins, but also the possibility of skin cancers.
• Visible range light. Spread over a range between 400 and 700 nm, it is about the various forms of light that make up the visible spectrum. If sunlight penetrates a prism, like raindrops in the atmosphere, we can see how it breaks down into its various wavelengths, which in our eyes constitute the different colors: violet (around 400 nm), blue (around 450 nm), green (around 520 nm), yellow (around 600 nm), orange (around 650 nm) and red (around 700 nm).
• Infrared range light. With a range between 700 nm and 1000 μm, it is the radiation that contributes the most amount of heat from the Sun. It is undetectable by the human eye and can in turn be divided into three types: near infrared (from 800 nm to 2500 nm), mid infrared (2500 nm to 50 μm) and far infrared (50 to 1000 μm).

Importance of sunlight

Sunlight is essential for our planet to be what it is, in a number of ways. On the one hand, its radiation provides the energy necessary to start various chemical reactions in the atmosphere and in the lithosphere primitive, whose immediate consequence was the formation of the ozone layer and the modification of the weather earth, which eventually led to the conditions conducive to the emergence of life.

Without sunlight, the photosynthesis it would not be possible and life would have had to turn to others methods to be produced, spread and evolve. Sunlight provides heat to the atmosphere, allowing the climatic seasons that form the cycle of the nature. Without sunlight, our world was likely to be a cold and dead one, as are the outer planets of the Solar System.

Sunlight on plants

Photosynthesis consists of a series of chemical reactions powered by solar energy.

Plants survive thanks to the use of inorganic elements such as Water, the carbon dioxide (CO2) and sunlight, thanks to a process of synthesis of biochemically usable sugars, known as photosynthesis. That is the reason why plants need to be exposed to the sun (in degrees according to the species, of course).

Photosynthesis is carried out by algae, cyanobacteria and all forms of vegetation, and consists of a series of chemical reactions driven by the energy of the Sun, which allows the formation of glucose according to the following formula:

6CO2 + 6H2O + E = C6H12O6 + O2

This process, as will be seen, by-produces oxygen that is released into the atmosphere, making it breathable for humans. animals. Once glucose is obtained through photosynthesis, plants can proceed to oxidize it regularly (cellular respiration), obtaining the ATP necessary to maintain your metabolism walking, growing, reproducing, etc.

Benefits of sunlight

Sunlight produces cholecalciferol, a natural antidepressant.

Exposure to sunlight has a number of positive effects on the human body, which go beyond providing us with perceptible heat and light to perceive the world around us. Among its benefits are:

• The metabolization of vitamin D. Indispensable for the fixation of calcium.
• The release of nitric oxide. Whose effect on the body includes the regulation of blood pressure.
• The production of cholecalciferol. A natural antidepressant whose levels fall in the populations exposed to dark winters and linked to summer depression.

Risks of sunlight

There is much debate as to whether sunlight is entirely beneficial or is also a risk factor for certain types of melanoma or skin cancer. Higher frequency forms of ultraviolet radiation are known to have a dramatic impact on DNA, so much so that they can be exploited as a germicide in laboratories. However, the levels of this light that normally fall on the earth's surface are not high; a situation that could have changed during the years when the ozone layer was weakened by air pollution, at the end of the 20th century.