Solar radiation is more than the light and heat that we perceive from the sun. The sun is a star, after all, and it produces energy in many forms, from perceptible heat, visible and invisible spectrums of light, radiation, and more. Life on earth would be impossible without the sun, but our atmosphere also protects us from the more dangerous aspects of solar radiation.
What is Solar Radiation?
Loosely defined, solar radiation is the total frequency spectrum of electromagnetic radiation produced by the sun. This spectrum covers visible light and near-visible radiation, such as x-rays, ultraviolet radiation, infrared radiation, and radio waves. The visible light and heat of the sun makes life possible, and is called daylight or sunshine. The earths atmosphere deflects or filters the majority of the suns harmful radiation, and our near-perfect positioning in the solar system allows us to receive the benefits proximity to the Sun without being baked or broiled like Venus or Mercury.
Life On Earth
Solar radiation is the basis for all life on earth. Autotrophs, organisms that produce their own food from the sun (mainly plants), use solar energy along with carbon dioxide and water to produce simple sugars in a process called photosynthesis. Heterotrophs, organisms that eat other organisms (like animals and fungi), depend on autotrophs to form the bottom level of the food chain. Heterotrophs couldnt exist without autotrophs, and autotrophs couldnt exist without the sun, so life as we know it depends on electromagnetic radiation.
Seasons and Climate
The Earths seasonal climate variation occurs as a result of minute changes in our planets distance from the sun during orbit. Solar radiation is also a contributing factor to the process of global warming. Even before modern human activity and fossil fuels began heating up the atmosphere, the elliptical path of the Earths orbit was creating 100,000-year cycles of warming and cooling that led to the ice ages and tropical periods of the distant past. Sunlight affects different parts of the Earth in different ways, with extremes manifesting in equatorial regions and the poles.
Our Relationship with the Sun
As human beings, we tend to have a love-hate relationship with the sun on one hand, sunlight keeps us warm, creates food and shelter for us via plant life, and gives us light. On the other hand, as greenhouse gases trap more heat and the ozone layer allows more dangerous UV radiation in, the suns rays can be distinctly dangerous. UV rays cause skin cancer in humans and animals, but can contrastingly improve other skin conditions like psoriasis. We need the sun biologically, as well, as it causes our bodies to produce vital vitamin D.
Solar radiation and sunlight make it possible for the Earth to house life. The negative aspects of our relationship with the sun are primarily the result of human irresponsibility: we develop skin cancer when we ignore our bodies signals to avoid sunlight, and we struggle with global warming because weve ignored the environmental concerns of our actions. When we dont give solar radiation the respect it deserves, we are literally playing with fire.