Sunlight

Sunlight is a compilation of photons emitted by the sun. These photons are responsible for bringing light, warmth, and illumination to Earth and other astronomical bodies. It takes sunlight 8.33 minutes to reach Earth. Sunlight is necessary for life to exist, both in plants and humans. Sunlight is different than moonlight or starlight. Sunlight and starlight are similar in that both are created from the source. However, the impact that starlight has on Earth is negligible. Moonlight is merely the reflection of sunlight. The composition of sunlight, as well as its speed, has been the subject of experiments since the time of the ancient Greeks and Romans. The Greeks and Romans understood that sunlight travels at an extremely fast speed. It was also thought that light was an element, until it was discovered to be a collection of photons.

Background

The study of sunlight has historically centered on its composition and speed. Theories have been proposed that sunlight is composed of particles, waves, or packets of energy.

The ancient Greek scientists were the first to try to understand the composition and speed of sunlight. They taught that sunlight is composed of fire and that it travels instantaneously. Some ancient Roman scientists, such as Lucretius, were forward-thinking, with beliefs in line with modern science. He believed that sunlight was composed of particles and traveled at a fast, finite speed.

The next advancement to the science of sunlight came about in the 1600s. During this century, Rene Descartes, Robert Hooke, and Christiaan Huygens each independently demonstrated experimentally that sunlight was composed of waves. Also during this time period, Ole Rømer proved that sunlight travels at a finite speed. Through experiments conducted via observation of Jupiter’s moons, Rømer confirmed the beliefs of Roman scientists, such as Lucretius.

Neither the exact nature of sunlight nor its speed was discovered until the twentieth century. In 1923, Arthur Holly Compton determined that sunlight was composed of photons through the Compton scattering experiments. While the precise speed of light was not known until 1975, throughout the century scientists had been refining the speed through more complex and precise experiments.

Overview

Sunlight is important for many aspects of life, including photosynthesis in plants, health considerations in humans, and warmth for all life on the planet. Additionally, sunlight provides perceived cosmetic benefits. However, sunlight can also provoke illnesses from too much or not enough exposure.

The sun provides light for the planet and drives photosynthesis. Photosynthesis is the process by which sunlight is converted into chemical energy for plants to use. Without the sun, the majority of plants could not exist. Through photosynthesis, plants turn sunlight into usable chemical energy. Plants are then consumed by animals and humans, transferring their energy. If photosynthetic plants were removed from the food chain, there would be no recognizable life on Earth.

The sun’s rays benefit human health in several ways. Sunlight has been used throughout history for its curative properties, and sunlight supplies vitamin D, an essential ingredient to health. Also, sunlight is responsible for mitigating certain psychological disorders, such as seasonal affective disorder, sleep arrhythmia, and depression. Psoriasis is a skin condition in which the skin is covered by scaly patches, which are extremely itchy. The sun is not a cure but can be a comforting measure.

Despite the health benefits, too much exposure to the sun’s rays can cause harm. Sunburns are directly related to exposure to sunlight. As the amount of time an individual spends in the sun increases, so does the seriousness and likelihood of becoming sunburn. Other harm includes cancer, skin degradation, snow blindness, and cataracts.

The sun is responsible for providing warmth on the planet. Without sunlight, Earth would become a frozen planet, much like the outer planets of the solar system.

The rays of the sun provide what some believe to be cosmetic benefits, as tan skin is often considered desirable. In ancient Egypt, Rome, and Greece, light-skinned individuals were considered more beautiful than those with dark skin tones. This is because those who had dark skin were the people who worked outside under the sun, whereas the people with light skin had the wealth to stay indoors and hire people to do their work. This perception has changed in the Western world in modern times. Now, despite adverse health effects, it is considered a sign of wealth and beauty when a person can tan and bronze their skin.

Bibliography

Blankenship, Robert E. Molecular Mechanisms of Photosynthesis. 2nd ed. Hoboken: Wiley, 2014. Print.

Choi, Charles Q. "Earth's Sun: Facts About the Sun's Age, Size, and History." Space.com, 23 Mar. 2022, www.space.com/58-the-sun-formation-facts-and-characteristics.html. Accessed 24 Nov. 2024.

Green, Adèle, et al. “Skin Exposure, Skin Cancers and Related Skin Conditions.” Supp. to Journal of Epidemiology 9.6 (1999): S7–S13. Print.

Han, Moo-Young. From Photons to Higgs: A Story of Light. 2nd ed. Hackensack: World Scientific, 2014. Print.

Herbert, Nick. Faster Than Light: Superluminal Loopholes in Physics. New York: Plume, 1989. Print.

Magueijo, João. Faster Than the Speed of Light: The Story of a Scientific Speculation. Cambridge: Perseus, 2003. Print.

Shamos, Morris H., ed. Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein. 1959. Mineola: Dover, 1987. Print.

"The Power of the Sun." National Geographic, 19 Oct. 2023, education.nationalgeographic.org/resource/power-sun/. Accessed 24 Nov. 2024.