Charles T. R. Wilson (1869-1959), Scottish physicist and Nobel laureate. Wilson invented the cloud chamber (see Particle Detectors), which gave the first pictures of the paths of subatomic particles (see Elementary Particles) and became an essential tool in the fields of atomic and meteorological physics (see Atom; Meteorology). For his discovery of the method of making the paths of electrically charged particles visible by the condensation of water vapor, Wilson shared the 1927 Nobel Prize in physics with American physicist Arthur Holly Compton.
Wilson was born in Glencorse in the former county of Midlothian, Scotland. He received a B.S. degree from Owens College (now the Victoria Institute of Manchester) in England in 1887 and a B.A. degree from the University of Cambridge in 1892. After teaching at Bradford Grammar School in Bradford, England, for four years Wilson returned to Cambridge in 1896 as a researcher and remained there, eventually as a professor, until he retired in 1936. He remained active in research, publishing his last paper at the age of 87.
Wilson first developed the cloud chamber in the late 1890s to study how water vapor and light interact. Physicists at that time thought that water droplets formed only around dust particles. Wilson established that water droplets can form around charged particles, or ions, in the absence of dust. He found that if he exposed the air in a chamber to X rays, many more droplets formed. He concluded the X rays give the air molecules an electrical charge, or ionize them.
As an ion moves through the cloud chamber, drops of water form around it. Because the ion moves very quickly, the string of drops of water in the air looks like a continuous path marking the movement of the ion. The path is especially apparent when a strong light is directed at the cloud chamber. If a magnetic field (see Magnetism) is applied to the cloud chamber, the ions will follow curved paths depending on the strength and nature of the charge, the mass of the ion, and the strength and direction of the magnetic field. The paths can be photographed for later analysis.
Wilson also intensely studied electrical conduction in air and applied his findings to devising ways to protect British airships from lightning and other discharges of electricity during World War I (1914-1918).
David Brewster (1781-1868), Scottish physicist, who discovered that light is polarized by reflection. He also invented the kaleidoscope.
Born in Jedburgh, Roxburghshire, Brewster studied for the ministry and served as a Presbyterian minister into his early 20s. He then left the clergy to pursue the study of science. While editor of the Edinburgh Encyclopedia, Brewster studied the properties of reflected, absorbed, and polarized light.
In 1815 Brewster observed that when a nonmetallic surface reflects light, partial polarization occurs, meaning that some of the light waves orient themselves in the same plane (see Optics: Polarization of Light). He also found that polarization increases as the angle of light rays becomes more of a glancing angle. Polarization eventually reaches the maximum point, known as the Brewster angle, and then decreases.
In addition to making microscopes and other optical devices, Brewster invented the kaleidoscope—a scientific toy that continues to entertain both children and adults. He devised the kaleidoscope in 1816 and then patented it, but even though thousands were sold in a short time, he ultimately earned nothing from it since it was an easy invention to copy. Brewster also invented the stereoscope, through which a viewer sees two slightly different pictures, one with each eye. The effect creates a three-dimensional illusion.
In 1819 Brewster was awarded the Rumford Medal by the Royal Society of London for his work with polarized light. He helped found the British Association for the Advancement of Science in 1831, and he was knighted in 1832. His books include Treatise on Optics (1831) and Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton (1855).
