Top 10 Thall's Scientist List
Johannes Kepler (1571-1630)
Modern astronomy begins with Copernicus (1473-1543) declaring (1530) the Earth rotates on its axis once daily and travels around the Sun once yearly. Next Tycho Brahe (1546-1601) made important contributions by devising instruments to observe motion of planets. In particular, Brahe compiled extensive data on the planet Mars. However, Johannes Kepler made the monumental discovery of the time. Brahe, fearing his bright assistant might eclipse him as the premiere astronomer of the day, assigned Kepler the perplexing orbit of the planet Mars (Mars has the most elliptical orbit of all the planets). Ironically it was precisely the Mars data that allowed Kepler to develop his three laws describing the orbit of planets around the Sun.
Kepler's Three Laws of Planetary Motion:
1. Planets revolve around the Sun in an elliptical path, with the Sun occupying one of the foci of the ellipse.
2. Straight line joining sun and planet sweeps out equal areas in equal intervals of time.
3. Squares of planets' orbital periods are proportional to the cubes of the semimajor axes of their orbits.
Galileo Galilei (1564-1642 
Mathematician/astronomer/physicist who made numerous contributions to modern science. Galileo was first to use telescope to gather evidence proving the earth revolves around the sun. His position represented such a radical departure from accepted thought that he was tried by the Inquisition in Rome, ordered to recant, and forced to spend the last eight years of his life under house arrest. But most of Galileo's projects didn't conflict with the church's interests?falling bodies, magnets, floating objects, the tides, compasses, arc of a cannonball, and rolling objects. He informally stated the principles later embodied in Newton's first two laws of motion. He also invented the mechanical pendulum clock, improved the telescope, and developed the first thermometer. Because of his pioneering work in gravitation/motion and in combining mathematical analysis with experimentation, Galileo is credited with ushering in the new age of science.
Sir Isaac Newton (1643-1727)
There can be no outstanding scientist list without Sir Isaac Newton; he made revolutionary advances in mathematics, optics, physics, and astronomy. In 1687 Newton published the Philosophiae naturalis principia mathematica. Principia, as it has become known, is recognized as the greatest scientific book ever written! Newton analyzed motion of bodies under the action of centripetal forces. The results were applied to orbiting bodies, projectiles, pendulums, and free-fall near the Earth. He further demonstrated planets were attracted toward the Sun by a force varying as the inverse square of the distance and generalized that all heavenly bodies mutually attract one another. In order to perform his calculations, Newton invented calculus.
Newton also explained a wide range of previously unrelated phenomena such as eccentric orbits of comets, tides and their variation, precession of the Earth's axis, and motion of Moon as perturbed by gravity of Sun. Newton was deeply interested in light and published optics in 1704. Although he believed a wave theory more probable, he relied on a corpuscular theory to account for phenomena such as reflexion, refraction, colors, and diffraction.
Newton's Three Laws of Motion:
1. A body continues in a state of rest, or motion with a constant velocity, unless compelled to change by an unbalanced force.
2. The acceleration of an object is directly proportional to the net force acting upon it and inversely proportional to its mass.
3. For every action force, there is an equal and opposite reaction force.
Charles Darwin (1809-1882)
Darwin studied medicine at Edinburgh University but was repelled by the sight of surgery performed without anesthesia and entered Cambridge University to become a clergyman. In 1831 after receiving his degree, Darwin served as an unpaid naturalist on the H.M.S. Beagle for a five-year scientific expedition to the Pacific coast of South America. The research resulting from this voyage formed the basis of Darwin's famous book, On the Origin of Species by Means of Natural Selection. Published in 1859, Darwin concluded:
1. Evolutionary change was gradual and required thousands to millions of years.
2. Primary mechanism for evolution was process called natural selection.
3. Millions of species alive today arose from single original life form through branching process called "specialization."
Variation within species occurs randomly and survival/extinction determined by organism's ability to adapt to its environment. Darwin's work had a tremendous impact on society since the theory challenged beliefs about the creation of life on earth. After publication of Origin of Species, Darwin continued to write on botany, geology, and zoology until his death in 1882. He is buried in Westminster Abbey.
Louis Pasteur (1822-1895)
French chemist/biologist who made numerous contributions to science including:
1. Separated mirror image molecules and studied effect of polarized light.
2. Demonstrated handedness of molecules from plant mold using one isomer of racemic acid.
3. Yeast is an organism and does not require oxygen for fermentation.
4. Pasteurization (mild heating) after fermentation kills microorganisms and prevents souring.
5. Identified parasite responsible for killing silkworms and saved French silk industry.
6. Proposed germ theory of disease urging doctors to use clean instruments, wash hands, and
disinfect bandages in The Germ Theory and its Application to Medicine and Surgery.
7. Developed treatment to prevent anthrax. Named technique "vaccination"' and applied it to
chicken cholera and rabies.
James Clerk Maxwell (1831-1879)
Maxwell is considered the scientist of the 19th century who had the greatest influence on 20th century physics. In 1931 Einstein described Maxwell's work as "the most profound and the most fruitful that physics has experienced since the time of Newton." Maxwell calculated the speed of propagation of an electromagnetic field as approximately that of the speed of light. He proposed the phenomenon of light is an electromagnetic phenomenon. In 1873 Maxwell published his Treatise on Electricity and Magnetism which contains his famous Maxwell equations; the four partial differential equations are one of the great achievements of 19th-century mathematics.
Maxwell also formulated, independently of Ludwig Boltzmann, the Maxwell-Boltzmann kinetic theory of gases. This theory showed that molecules at high temperature have only a high probability of moving toward those at low temperature. Maxwell's approach did not reject the earlier studies of thermodynamics but used a better theory of the basis to explain the observations and experiments.
Emil Fisher (1852-1919)
No one made greater contributions to chemistry than Fisher. In his early years developed new dyes and identified the active ingredients in tea/coffee/cocoa. Between 1882-1906 Fisher performed perhaps the most outstanding work in the history of chemistry. He established structures for the 16 stereoisomers of the aldohexoses (C6H12O6)?glucose being the most prominent member. In the process he synthesized glucose, fructose and mannose starting with glycerol. In other work he showed substances such as adenine, xanthine, caffeine, uric acid, and guanine all belonged to the family he called purines. Fisher advanced our knowledge of protein by developing methods to separate/identify individual amino acids. He also synthesized proteins and identified the peptide bond holding them together in chains. Fisher devised cross representations (today called Fisher projections) and proposed the often used lock & key model to explain the fit of a drug onto a receptor site.
Albert Einstein (1879-1955)
Einstein is probably the most famous scientist of all time. He burst on the scene in 1905 when he managed to solve three of the outstanding problems of physics: photoelectric effect, Brownian motion, and special theory of relativity. These three publications have become known as the "Einstein trilogy."
Einstein's greatest work occurred in 1915 when at the "advanced age" of 36, he published the general theory of relativity showing that gravity and acceleration are the same.
Edwin Hubble (1889-1953)
In 1924 Hubble measured the distance to the Andromeda nebula and showed it was about a hundred thousand times as far away as the nearest stars. It had to be a separate galaxy, comparable in size to our own Milky Way but much further away. Hubble began to classify galaxies according to their content, distance, shape, and brightness patterns. By observing redshifts in the light wavelengths emitted, Hubble concluded that galaxies move away from each other at a rate dependent to the distance between them (Hubble's Law). The further away they were the faster they receded. Hubble calculated the point where the expansion began and estimated the age of the universe at about 2 billion years (more recent estimates put it at 20 billion years). No person had a greater impact in determining the extent of our universe than Edwin Hubble. From proving that other galaxies existed to proving that galaxies move apart from one another, Hubble's work defined our place in the cosmos. In honor of Hubble's achievements, the Orbiting Space Telescope was named after him.
Paul Dirac (1902-1984)
Considered the second outstanding scientist of the 20th century, Dirac was one of the pioneers of quantum mechanics and developed the first theory of the electron that took into account special relativity. The theory described many observed attributes of the electron that previous theories had been unable to anticipate. But the most remarkable prediction of the theory was that the electron should have an anti-particle associated with it, having the same mass, but with a positive instead of negative charge. In 1932 this particle?later called the positron?was discovered, and since then many other anti-particles have been predicted and observed. Dirac developed a version of the Schrödinger Equation, known as the Dirac Equation, which is relativistically correct. For his work on anti-particles and wave mechanics, he received the Nobel Prize in physics in 1933. Dirac was Lucasian Professor of Mathematics at Cambridge from 1932 to 1969 and professor of physics at Florida State University from 1971 until his death.
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