How Does Sunlight Affect the Earth?

Sunlight, which comes from the sun, is a powerful energy source. Traveling through space at nearly three hundred and sixty thousand kilometers per second, sunlight travels to the Earth and strikes it mainly reflected, although some of the light bounces back into space. The rest is absorbed and serves as a source of energy for processes within the atmosphere and hydrosphere. The composition of Earth’s surface determines how much solar radiation reaches the planet, and its variation can have a dramatic effect on global climate, ecosystems, and other factors.

Solar radiation

The Sun’s radiation and light energy are the primary components of the sun’s climate. Earth receives roughly one-fifth of this energy, but the amount varies throughout the day based on various atmospheric and astronomical factors. The total solar energy reaching Earth is approximately the same as its radius. The maximum intensity of sunlight is received by the Earth’s surface where the sun is directly overhead, known as its zenith. The intensity of sunlight on horizontal surfaces decreases as the sun’s position is lower. Because of Earth’s rotation, the amount of sunlight reaching Earth changes daily.

A quantification metric is a way to measure the amount of solar radiation reaching a given surface area. Quantifying the solar radiation received by a building’s surface area can provide a visual representation of the radiation levels, but it’s still an abstract metric. A solar access metric is a useful tool, but it doesn’t communicate the quality of a design. It’s important to know when to use a quantification metric and the time constraint you choose.

UV radiation

While UV levels are present all year round, their intensity varies with location. UVA rays stay relatively constant throughout the day, while UVB rays fluctuate in intensity depending on the position of the sun. Higher the sun’s position, the higher the UVB intensity. UV levels also vary with time of day and latitude. In general, UV levels are higher near the Equator and lower at lower latitudes.

Overexposure to UV rays can have serious health consequences, ranging from skin cancer to premature aging of the skin. It can also affect the eye and suppress the immune system. It is important to educate children about the dangers of UV radiation, as too much exposure to sunlight can increase their lifetime risk for developing melanoma. Exposure to sunlight without protection increases the risk of developing skin cancer. Even people who do not burn themselves are exposed to high levels of UV radiation, which can lead to skin cancer.

X-rays

The sun’s X-rays are made of soft X-rays, which carry information about the solar process. The data is different from previous studies, but the researchers say they have discovered that the corona contains many atoms that are much more abundant than on the solar surface. Nonetheless, this new discovery is still controversial. Scientists still don’t fully understand the solar process, but soft X-rays offer a new way to investigate the sun’s activity cycle.

Massive stars produce large fluxes of radiation, and the matter at the surface of these stars is blown outward by stellar wind. Despite being so massive, the radiative driving mechanism is unstable and subject to velocity perturbations. Such perturbations steepen into strong shocks and convert wind kinetic energy into thermal gas energy. The relative velocities and temperatures should reach millions of degrees, producing observable X-rays. In addition, the X-ray emission is proportional to the total power radiated through all wavelengths.

Radiative heat

The process by which radiant heat is transferred without physical contact is called radiative transfer. The sun is the largest source of radiative heat on earth, and it travels through space in electromagnetic waves. This energy warms the earth during daylight hours. While you may not feel the warmth of the sun, you will feel the heat of the fire when you stand near it. Because these waves travel in straight lines, it can be deflected by a reflective surface.

The amount of radiation varies with temperature, and it is directly proportional to the fourth power of the absolute temperature of the object. The greater the surface area, the higher the amount of radiation. In order to understand the effect of radiation, it is helpful to first understand the science behind the temperature dependence of heat transfer. The heat transfer rate increases linearly with surface area, and a larger area will produce more radiation than a smaller area.

Photoprotection

Most of the UV radiation reaching the surface of the earth is ultraviolet A (UVA) (320-400 nm). UVA2 is 25 percent of this band and has similar effects on the skin to UVB. UVA1 is much less powerful and has decreased erythema generating potential. Both UVA and UVB are known to cause skin aging and may even contribute to skin carcinogenesis. Several approaches to photoprotection are now available. These include UV-filters, skin-protective clothing, and nutritional supplements.

One study found that sequential topical applications of DHA and naphthoquinone at bedtime improved UVR protection in 30 UVA/B/Soret band-photosensitive patients. This treatment was associated with no therapeutic failures or patient loss to follow-up. Two additional studies extended the limits of photoprotection in 18 patients over seven months. Using a questionnaire-based study design, the authors reported a sun protection factor of 3.

Climate change

There is a big question mark over the relationship between climate change and the Sun. While human-induced increases in CO2 concentrations have been the dominant cause of the long-term rise in global surface temperature, other influences, such as changes in solar activity, are likely to be responsible for these changes. Further, the changes in the CO2 content of the atmosphere could be responsible for the drop in sea-surface temperatures. So, does the Sun really play an important role in climate change?

A recent study in Nature published in Science Advances showed that increased solar energy would cause global warming, since it would heat the entire atmosphere. The increase in greenhouse gases has already accelerated the melting of major ice sheets in Antarctica, causing several feet of sea level rise. Heat waves are becoming longer and more frequent, which indicates climate change is human-induced. It will take years before the change becomes significant enough to affect the oceans and human life.