Tyndall John 182093

john tyndall was born in Leighlinbridge, County Carlow, in Ireland on August 2, 1820. After working as a surveyor and a mathematics teacher, he attended the University of Marburg in Germany, where he received his Ph.D. In 1854, he became a professor of natural philosophy at the Royal Institution in London (a scientific research center founded in 1799). In 1867, he was made superintendent of the institution, taking over from Michael Faraday.

Tyndall's most well-known scientific studies included the nature of sound, light, and radiant heat and observations on the structure and movement of glaciers. Glaciers had become a scientific area of interest during that time because in the 1830s, Louis Agassiz (considered the father of glaciology) had discovered that a large portion of Europe and North America had once been covered with ice.

Tyndall developed an interest in meteorology as a result of his love for mountain climbing. He studied alpine glaciers and took meteorological

John Tyndall was a 19th-century physicist. He is renowned for his studies in the absorption of heat by atmospheric gases.

Maria Borovnik Massey University

John Tyndall was a 19th-century physicist. He is renowned for his studies in the absorption of heat by atmospheric gases.

measurements on Mont Blanc in the Alps. Using a spectrophotometer he designed, Tyndall studied the absorption of infrared light (at the time called radiant heat) by atmospheric gases. Infrared light is felt as heat and has wavelengths of approximately 0.7 to 1.0 pm. Visible light for comparison has wavelengths of approximately 0.4 to 0.7 pm.

Some of the invisible gases (oxygen, nitrogen, and hydrogen) were transparent to radiant heat, whereas water vapor and carbonic acid (now known as carbon dioxide) absorbed and reemitted infrared light, thereby warming the atmosphere close to the earth. From these experiments, Tyndall realized that water vapor, carbon dioxide, and ozone—even in small quantities—were the best absorbers of heat radiation, and he later speculated on how changes in these gases could correlate to climate change.

GREENHOUSE GASES

Among the various atmospheric gases in the troposphere, Tyndall discovered the importance of water vapor and carbon dioxide as greenhouse gases that trap heat on the surface of the earth. Without these atmospheric gases to trap heat, the heat would rapidly radiate back into space, and the Earth would be much colder. During cold nights, there is an enhanced chance of fog or dew in the mornings because the moisture in the air (water vapor) condenses into droplet as the air cools. In deserts—hot and dry climates—there is a lack of water vapor in the air, and the sand radiates heat easily into space. Changes in the atmospheric levels of gases produce changes in the climate as well.

In the 1860s, Tyndall began to suggest that slight changes in the atmospheric composition could bring about climatic variations. Tyndall was the first scientist to explain the Ice Ages as being caused by greenhouse effect. In particular, he noted that variations in water vapor resulted in a change in the climate and realized the importance of the greenhouse effect in maintaining ecosystems necessary for life. He thought changes in the composition of the atmosphere may have produced all changes in the climate.

Using the laws of thermodynamics, Tyndall proposed that changes in carbon dioxide cause an initial change in temperature, and when the humidity changes accordingly, the change in humidity leads to a second change in the temperature.

During the Victorian era, he was the contemporary and friend of other important scientists. In addition to his scientific research, he promoted scientific education of the public with scientific demonstrations and advocated using hands-on laboratory experimentation to teach science. In 1874, Tyndall used his address before the British Association for the Advancement of Science to proclaim rational thought and skepticism as the aim and superiority of science.

In the 1870s, he made a lecture tour of the United States and included his lab demonstrations. Over the course of his professional life, he was the recipient of numerous scientific awards and recognition. In addition to his dynamic public speeches using laboratory experimentation, he published a wide range of papers, treatises, and books. Digital versions of John Tyndall's books can be found at http://books.google.com and include Lectures on Light Delivered in the United States in 1872-1873, first published in 1873; Hours of Exercise in the Alps, first published in 1871; and The Glaciers of the Alps, first published in 1861.

John Tyndall died on December 4, 1893, from an overdose of chloral hydrate. At the inquest, his wife testified she mistakenly gave him chloral hydrate instead of his normal medication, leading to his death.

TYNDALL EFFECT

The Tyndall effect, a scientific principle on the dispersion of light beams through colloidal suspensions or emulsions, was named for him. The importance of his research continues, as his work continues to shape scientific research on climate change.

The Tyndall Centre, with headquarters at the School of Environmental Sciences at the University of East Anglia, founded in 2000, is named after John Tyndall, in honor of his being one of the first scientists to recognize the Earth's natural greenhouse effect and observing, identifying, and proposing the climate effects of the radiative properties of atmospheric gases. The mission of the Tyndall Centre is to research and educate policymakers on climate change, to develop and apply research methods for climate change, and to promote international dialogue on managing future climate change.

In support of this goal, research at the Tyn-dall Centre includes action to provide information through data collection and interpretation and modeling to assess possible scenarios of the effect of human and natural causes on climate change and to disseminate this information by encouraging international discussion and policymaking. By using empirical research, the Tyndall Centre proposes protection of coastline ecosystems, city-scale emissions testing, and accountability for contributions to climate change. The Tyndall Centre focuses on this objective, with a strategy to investigate and identify behavior modification and education opportunities to promote sustainable approaches to limiting human-induced climate change.

SEE ALSO: Carbon Dioxide; Greenhouse Effect; Greenhouse Gases.

BIBLIOGRAPHY. Mark Bowen, Thin Ice: Unlocking the Secrets of Climate in the World's Highest Mountains (Henry Holt, 2005); Earth Observatory, "John Tyndall," www.eobglos-sary.gsfc.nasa.gov; Tyndall Centre, "Research at the Tyndall Centre," www.tyndall.ac.uk (cited July 2007).

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