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Hermann Ludwig Ferdinand von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz , 1821-94, German scientist. Although known especially as a physicist and biologist, he was also a physician, mathematician, philosopher, and lecturer on popular science. He extended the application of the law of conservation of energy and in 1847 formulated it...
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Christine Ladd-Franklin
Christine Ladd-Franklin 1847-1930, American scientist, b. Windsor, Conn., grad. Vassar 1869. She was the first woman student to enter Johns Hopkins (1878), her special studies being directed toward logic and the theory of color. She studied in Göttingen (1891-92) and worked in Helmholtz's labo...
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ophthalmoscope
ophthalmoscope , instrument used for examining the inner structure of the eye . The device was invented by the German physiologist H. L. F. von Helmholtz in 1851. His model consisted of three plates of glass pressed together and mounted on a handle at a 45° angle. A light was placed beside the ...
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Thomas Young
Thomas Young 1773-1829, English physicist, physician, and Egyptologist. He established (1799) a medical practice in London and was elected (1811) to the staff of St. George's Hospital there. His lectures while professor of natural philosophy (1801-3) at the Royal Institution, London, published as ...
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vision
vision physiological sense of sight by which the form, color, size, movements, and distance of objects are perceived.
Vision in Humans
The human eye functions somewhat like a camera; that is, it receives and focuses light upon a photosensitive receiver, the retina. The light rays are be...
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George Ellery Hale
George Ellery Hale 1868-1938, American astronomer, b. Chicago, grad. Massachusetts Institute of Technology, 1890. He founded and directed three great observatories (Yerkes, Mt. Wilson, and Palomar), each in its time the greatest in the world, and was active in organizing interdisciplinary scientifi...
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vortex
vortex , mass of fluid in whirling or rotary motion. To simplify the analysis, vortex motion usually describes motions in a frictionless fluid. In such cases the absence of friction would make it impossible to create or to destroy vortex motion. Motion in such a fluid would be a permanent flow patte...
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psychology
psychology science or study of the thought processes and behavior of humans and other animals in their interaction with the environment. Psychologists study processes of sense perception , thinking, learning , cognition, emotions and motivations , personality , abnormal behavior, interactions b...
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sun
sun intensely hot, self-luminous body of gases at the center of the solar system . Its gravitational attraction maintains the planets, comets, and other bodies of the solar system in their orbits.
General Characteristics of the Sun
The sun is actually a star of about medium size; it appe...
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physics
physics branch of science traditionally defined as the study of matter , energy , and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this name at a few universities. Physics is in some senses the oldest and most basic pure science; it...
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