Nicolas Copernicus' Revolutions of Celestial Orbs assigned three motions to the hitherto stationary Earth: daily spinning, annual circular revolution, and a gyrating axis. The book initiated a profound change in cosmology and physics, and radically altered the Christian-Aristotelian view of peoples' place in the center of the universe.

Ambroise Paré, an unschooled military surgeon, devised new, effective procedures and instruments for bone fractures, childbirth, and amputation. He became famous for removing darts and arrowheads effectively, and for treating gunshot wounds with dressings instead of burning them with hot oil.

Tycho Brahe's accurate astronomical observations enabled Johannes Kepler to validate Copernican astronomy. On the basis of mathematiccal and physical arguments, Kepler devised three new laws of the varying speed of planets in their orbits. In turn, mathematical laws greatly simplified and improved the Copernican descriptions of planetary motions measured by Brahe.

Measurements of body functions in quantitative, physical terms by Sanctorius Sanctorius made him a pioneer of modern physiology. He invented a pulse clock and an apparatus--which he used on himself for years--to measure body weight changes due to digestion, excretion, and respiration.

By careful and systematic experiments, William Gilbert established the basic modern facts of magnetism. However, a magical world still filled his thinking. Gilbert believed the immaterial powers of magnetism present in all matter were occult forces.

John Ray and Joseph Tournefort called attention to classification rather than collection. They helped to clarify the difficult definitions of "species" and "genus," and ordered flora and fauna by their physical features, such as leaf and flower, toe and tooth.

The century of the Great Plague saw outbreaks of malaria, scarlet fever, smallpox, and other epidemic diseases. Thomas Sydenham promoted new treatments for these illnesses. He observed his patients carefully, and prescribed simple, specific remedies. He helped turn other doctors' attention from theory and toward treatment and self-healing.

The invention of the microscope raised new questions about animal and plant life. Marcello Malpighi observed capillaries for the first time, and Leeuwenhoek discovered blood corpuscles. Robert Hooke and Nehemiah Grew examined the cellular structure of seeds and plants.

The discovery of ova by Nicolaus Steno and Regnier de Graaf supported the century-old belief that babies developed from the miniature human beings inside a human egg that was triggered to develop by male semen. Antony van Leeuwenhoek's discovery of microscopic sperm in semen led to the belief that it was the sperm that contained preformed humans, which the egg simply nourished.

Galileo Galilei's discovery of new celestial phenomena, such as Jupiter's moons and the phases of Venus, supported Copernicus' ideas about astronomy. Galileo's experimental and mathematical studies of falling bodies and projectiles led to new unified laws of terrestrial and celestial mechanics, but his ideas were strongly condemned by the Catholic Church.

William Harvey proposed that blood flowed continuously in one direction: away from the heart by arteries and back to the heart by veins. His quantitative experiments of blood flow and his mechanical explanations of the heart's one-way valves revolutionized the study of the human body.

René Descartes said "I think, therefore I am." He sought to explain the universe by the skeptical power of reason alone. Descartes' fantastic schemes of matter composed of colliding particles stimulated others to search for mechanical forces behind all physical events.

Experiments with a new mercury barometer led to demonstartions of the mechanical weight of air and the existence of a vacuum. Robert Boyle's experiments with the new vacuum pump of Otto von Guericke showed that air was an elastic fluid whose pressure varied inversely with its volume.

Nicolaus Steno challenged the century-old belief that the Earth had remained unchanged since its creation. Steno took the dynamic view, based on his observations of layers in the Earth's crust. These different strata, he believed, had been left by former seas, which were altered by erosion, earthquakes, and volcanic eruptions.

Isaac Newton's innovative experiments with lenses and prisms and his speculations on the particle nature of light led to an intense controversy with Christian Huygens. Huygens argued that light was a form of wave motion in an all-pervasive, mechanical "ether." Newton's particle theory of light became dominant for over a century.

Isaac Newton's interests in alchemy and biblical chronology were overshadowed by his three new mathematical laws of motion and his universal law of gravitation. Newton's Mathematical Principles of Natural Philosophy was the climax for the experimental, mechanical, and mathematical approaches of the 17th century scientific revolution.

The independent invention of calculus by Isaac Newton and Gottfried Leibniz led to intense debates over who should get the credit for its discovery. Newton's vague theory of "fluxions" led his followers to adopt Leibniz's version of differential and integral calculus.

In René Descartes' famous book on human phisiology, he separatede the body's mechanical actions from the mind's thoughts. He pictured a nervous system of valves and tubes which caused muscles to contract by reflex. The mind also could command the nerves to make the muscles move.

People either explained the functions of life in terms of physical-chemical principles or by nonmechanical "vital" forces. Stephen Hales conducted experiments on plant sap and explained his findings in terms of the mechanical pressure of fluids.

One of the most important disputes in the history of science raged over the question in mechanics: What was the correct measure of the force of a moving body---momentum or "vis viva" (kinetic energy)? Many measuring machines later, with no winners or losers, both were regarded as equally valid concepts.

The two greatgest naturalists of the century, Carolus Linnaeus and the Comte de Buffon, both believed that there are distinct forms of life called species, but disagreed over how to define them. Buffon rejected Linnaeus' artificial system of plant classification by their sexual parts.

When James Cooke sailed around the world, the botanist Joseph Banks was on board. Banks collected many samples of plants, mammals, and fish. Expeditions like this one were the source of new knowledge and new questions about different species and their geographical distributions.

The demonstration that covered meat did not produce maggots failed to shake some peoples' belief that life could arise spontaneously---without a physical source. Lazzaro Spallanzani showed that prolonged boiling of tightly sealed liquids eliminated the probable, pre-existing life sources.

The widespread belief in preformism---growth from a microscopic replica of the adult form---was challenged by Kaspar Wolff and others. Their observations of the step-by-step development of embryos from uniform tissues to complex organs led to the acceptance of the epigenesis---gradual development---theory.

Hermann Boerhaave was the most renowned medical teacher, lecturer and clinician of the early 1700s. He supplemented his formal lectures with bedside teaching and remedies based on practical experience. To Boerhaave, the patient, rather than the theory or experiment, came first.

Experiments with the generation, conduction, induction, and storage of electricity led to differing theories. Charles Du Fay hypothesized that there were two kinds of electricity which were self-repulsive but also attractive to each others. Benjamin Franklin's "one fluid" electricity that could not be created or destroyed, only transferred, became widely accepted.

Using Newton's law of gravitation to compute the parabolic orbits of known comets, Edmund Halley discovered that three known comets had the same orbit. Figuring that it might be just one comet seen three times, he predicted that the comet would reappear in 1758. The comet's arrival on schedule was hailed as a triumph of Newtonian science.

The most respected and productive mathematical scientist of the 18th century was Leonhard Euler. Euler made significant contributions to nearly every field of pure and applied math: calculus, algebra, number theory, analytic geometry, mechanics, and the three-body motion of the sun, Earth, and moon that had baffled even Newton.

Comte de Buffon challenged the long prevailing static view of geology. Physical evidence led him to conclude that the Earth had changed successively since creation. His estimate of the Earth's age of 70,000 years far exceeded an estimate of 6,000 years based upon the Bible.

At the age of 79, Geovanni Morgagni published his monumental book on the sites, causes, and appearances of diseases, based on several hundred human dissections. Morgagni's success in relating symptoms with autopsy findings opened up a new medical discipline called pathological anatomy.

Most geologists favored Abraham Werner's "Neptunist" explanation of the Earth's geological strata: Successive layers of rocks with fossils are the sediments from a single, primeval ocean. Less popular was James Hutton's theory of slow-acting, constant forces of erosion and uplift throughout time.

With an electrically charged pith ball suspended from a delicate torsion balance. Charles Coulomb showed that electric forces of both attraction and repulsion varied inversely with the square of the distance, just like gravitation. This precise quantitative experiment significantly broadened Newton's theory of physical forms.

Benjamin Thompson (Count Rumford) raised doubts in the prevailing theory of heat by showing that unlimited heat could be produced by friction. He had no alternative explanation, however, and failed to alter others' acceptance of the caloric substance theory.

Henry Cavendish provided the first direct experimental evidence of Newton's law of gravitation. He measured the minute force of attraction between two balls with a delicate torsion balance. Knowing that force enabled him to measure the mass and density of the earth.

Marie Bichat's experiments focused doctors' attention on tissues (bone, muscle, nerve, etc.) as the primary site of disease. He also pioneered a "vitalistic hierarchy" of human biology: tissues from organs, organs make up systems (digestion, respiration, etc.) which perform the two main functions of growth and movement.

Using mathematics, Pierre Simon de Laplace showed that the motions of the moon and planets could be predicted completely by Newton's universal law of gravitation. All apparent variations were simply periodic over long time spans. The solar system was finally seen as an immense, self-regulating mechanism, driven by natural forces of gravity between massive bodies.

Georges Cuvier viewed each life form as a unified system of related parts and set new standards for comparative anatomy. He thought that the function of every animal was determined by the shape of its limbs or organs.

Thomas Young's new principle of wave interference enabled Augustin Jean Fresnel to account for his experiments on diffraction and polarization of light, as well as all the other known optical effects. The Young-Fresnel theory rapidly replaced Newton's long-standing particle theory.

Fossil studies led Georges Cuvier and Jean Baptiste de Lamarck to the same conclusion: simple organic forms were in the oldest rocks and complex forms were in the recent layers. They disagreed strongly on how to interpret this observation. Cuvier believed that catastrophes happened. Lamarck believed in a gradual transformation of life.

The presence of dark lines in solar spectra and in light that had passed through gases remained a puzzle for a long time. Georg Kirchhoff established that all chemical elements had their own characteristic pattern of the spectra, like chemical "fingerprints." This work raised new questions about the structure of chemicals on the Earth and in the stars.

The accidental discovery by Hans Oersted that an electric current could move a nearby magnetic needle led André Ampère to derive mathematically and verify by experiment the magnetic force between twso current-carrying wires. Michael Faraday soon discovered another new but different interaction between electricity and magnetism called induction.

Several novel forms of non-Euclidean geometry were invented in the 19th century by Nikolai Lobachevsky, János Bolyai, Karl Gauss and Georg Reimann. Their work on curved surfaces shattered the old belief that there could be only one geometry and that geometry must correspond to real physical space.

On the basis of magnetic and electrochemical experiments, Michael Faraday proposed that magnetic and electrified bodies set up internal and external fields of forces. James Clerk Maxwell's prediction that light was a special form of wave in an electromagnetic field was verified experimentally by Heinrich Hertz.

A young French engineer, Sadi Carnot, wrote a book on how to produce work in a steam engine merely by heat transfer. Although it was not widely read, it did become the basis of Rudolf Clausius' inspiration for the Second Law of Thermodynamics, which involves the natural tendency for temperature differences to equalize.

Ingenious experiments with a torsion balance and thermoelectric currents led George Ohm to formulate a basic theoretical relationship between electric currents, voltage, and resistance in a circuit. Disappointment from the lack of recognition later caused Ohm to abandon his electrical research.

Publication of Charles Lyell's Principles of Geology brought together 30 years of geological findings and started the downfall of the catastrophe account of the Earth's history. Lyell demonstrated that all past geological and biological changes were continually produced by the same physical forces still existing today.

Matthias Schleiden and Theodor Schwann proposed that all plants and animals were constructed of cells---tiny walled structures containing a nucleus and protoplasm. Newly optically improved microscopes confirmed the cell hypothesis.

In the mid-19th century, three radically new types of algebra were created in England. Abandoning the commutative rule of multiplication, William Hamilton invented quaternionic algebra, and Arthur Cayley invented matrix algebra. George Boole devised a new algebra of "sets," which don't conform to some ordinary algebra rules.

The greatest spokesman and practicioner of experimental biology was Claude Bernard. He said that the only way to understand life's phenomena and relationships was by controlled scientific experiments. The ultimate causes for life, however, were considered to be beyond the realm of science.

Independent experiments by James Joule, Julius Mayer, and Ludwig Colding, and theoretical analysis by Hermann von Helmholtz, led to the principle that the total amount of energy remained constant, or "conserved" during conversions of one form of energy into another.

Differences between the observed and predicted motion of Uranus led Urbain Leverrier and John Adamsto account for the deviations by the gravitational pull of a new, unknown planet. Their predictions were confirmed by the discovery of Neptune.

Research and arguments by a medical microscopist, Rudolf Virchow, established the cell as the fundamental site of the disease. Virchow defined the similarities between diseased cells and normal cells. This relation changed the objectives and methods of pathology and helped create the new science of cytology--- the study of cells.

James Clerk Maxwell proposed his "demon paradox" to prove that a mechanical account of the Second Law of Thermodynamics had to be statistical. Prominent physicists questioned his mechanical interpretation of heat.

Discovery of fossil human bones in prehistoric limestone in the Neander Valley in Germany, of Cro-Magnon man in France, and Pithecanthropus in Java established our ancient past. The relationship of these prehistoric humans to modern humans is still debated today.

Charles Darwin and Alfred Wallace proposed a radical new theory of evolution based on the "natural selection" of all life forms. A storm of controversy erupted over the place of humans in evolution. The theory upset people's idea of their unique biological and moral place on Earth by associating them with other animals and the natural laws that govern them.

Earnst Haeckel combined two theories--Baer's theory of embryo development and Darwin's new theory of organic evolution---and proposed that the development of an individual embryo repeated the same evolutionary stages of its ancestors. Haeckel's "recapitulation" theory quickly gained wide acceptance, despite counterevidence.

Studies of microscopic organisms demonstrated what had long been suspected. Specific bacteria or germs were the causes of specific diseases. Louis Pasteur extended this idea medically by showing that inoculations of mild forms of diseases, such as rabies, could prevent severe illness.

To explain his observations from cross-breeding pea plants, Gregor Mendel assumed that every plant contained two "factors"---one dominant, the other recessive---for each inherited feature. His scheme was rediscovered and accepted several decades later as the basic law of heredity in all plants and animals.

From his cross-breeding of primroses, Hugo de Vries proposed that new species arose from "mutations," spontaneous changes in genetic material inherited by offspring. De Vries received widespread acclaim, but praise soon died when it was found that the primrose was the only plant that produced such large variations in a single generation.

Wilhelm His rejected the idea of parallels between embryology and evolution and sought to discover the physical and chemical causes for embryonic development. His new experimental approach gained many followers, including Wilhelm Roux who studied the internal responses of an egg to an altered physical environment.

There were striking parallels between the designs of Elisha Gray and Alexander Graham Bell, who competed to make the first telephone. Bell filed a patent application earlier on the same day as Gray and was awarded the patent. Gray didn't contest the decision, believing that the telephone would have little commercial value.

There was a growing concern among mathematicians that the foundations of analysis---the study of series and their limits---were not well understood. Karl Weiershass and Georg Cantor labored to base analysis solely on number theory. Their work had profound effects on 20th century mathematics.

Gottlieb Daimler patented a small, high-speed, four-cylinder internal combustion engine with a single verticle cylinder. He first mounted this engine on a wooden bicycle and then on a four-wheel horse carriage. These motor vehicles were the direct forerunners of our modern automobiles.

Was the medium producing light waves stationary or moving relative to the motion of the Earth? This question perplexed no one more than Albert Michelson and Edward Morley. Their precie measurements of light failed to detect the expected "ether wind." The result perplexed many scientists.

Joseph John Thomson's novel experiments on the properties of "cathode rays" passing through gases led him to conclude the there were minute particles carrying negative charges. He suggested that they were the basic building blocks of the atoms of all the chemical elements.

Seeking to explain the energy distribution of electromagnetic radiation inside a black box. Max Planck suggested that the exchange of energy had to take placed in discrete, quantized units. This radical idea contained the seed of an entirely new direction in physics for the 20th century.

From studying the Indiana dunes, Henry Cowles established several basic principles of ecology. He observed that as plants grow they alter the environment , which can make other plants more competitive. Whole plant communities can succeed one another in predictable stages, transforming barren environments into complex eco-systems.

Guglielmo Marconi's invention of sending wireless messages in Morse code by electromagnetic waves across the Atlantic astonished the world. It also inspired Lee de Forest to invent the triode vacuum tube, which amplified received or transmitted signals. This device made possible radio and television transmission.

Albert Einstein made the revolutionary proposal that when light was emitted or absorbed it behaved like a particle, called a "light quantum." The idea seemed to explain the scattering of x-rays off electrons, but when x-rays passed through crystals, fhey were diffracted as waves. This uzzling wave-particle duality of light was resolved by the new quantum theory.

Based on his observations of mutations in fruit flies, Thomas Hunt Morgan discovered that certain features of heredity were linked to genes on sex chromosomes. This realization paved the way for locating different discrete genes on other chromosomes. Morgan's experiments also indicated the source of variation in Darwin's theory.

Joining the ideas of evolution and heredity required the work of many biologists. By studying experimentally the genetics of whole populations (rather than single individuals), biologists were able to show a relationship between particular chromosomes and particular types of environments. They then could relate genetic distribution of populations to Darwin's idea of natural selection.

To know the exact molecular structure of proteins required the development of three new techniques: the crystallization of a pure substance, the ability to combine large numbers of amino acids, and a method for isolating and identifying different amino acids. Frederick Sanger used all of these to reveal the complete amino acid structure of an insulin protein.

James Chadwick's experimental discovery of the neutron led to a novel model of the atom's nucleus. Wolfgang Pauli and Enrico Fermi proposed that when a neutron (n) changed into a proton (p), the emission of an electron (e^-) was accompanied by another new particle, the neutrino. These understandings confirmed a new notion of "weak" nuclear forces.

Lew Landau suggested that a massive star collapsing could trap all matter and light within it, creating an invisible "black hole." Using Einstein's general theory of relativity, J. Robert Oppenheimer and Hartland Snyder showed how this collapse could occur. Some astronomers believe that one candidate for a black hole, Cygnus X-1, has been found.

Japanese physicist Hideki Yukawa suggested that the cohesive forces in an atom's nucleus were due to "meson" particles that were continuously exchanged between protons and neutrons. After such a particle was detected in cosmic radiation, Yukawa became the first Japanese to be awarded the Nobel Prize.

Deflections of x-rays off crystals revealed the regular three-dimensional spacing and orientation of molecules. This technique enabled John Kendrew and Max Perutz to disclose the complex molecular structure of proteins, and to show how protein form determines function.

Continuing differences between observed and predicted positions of Uranus and Neptune prompted the search for an unknown planet whose gravity was affecting those planets' motion. Clyde Tombaugh's detailed photographic analysis of its most probable location finally revealed Pluto, the farthest planet from the sun.

From their intricate experiments involving inheritable changes that occurred when different forms of pneumonia bacteria were mixed together, Oswald Avery, Colin MacLeod, and Maclyn McCarty proposed that DNA (deoxyribonucleic acid), not protein, was the hereditary material responsible for those transformations. This view was received with skepticism until experimental evidence for it was presented by Alfred Hershey and Martha Chase.

George Gamow proposed that the present universe had come from a primeval explosion of a hot, dense state of space, matter, and radiation some 15 billion years ago. Accidental detection of the radiation left over from that "big bang" by Arno Penzias and Robert Wilson provided strong evidence for Gamow's theory, and against the steady state theory of Fred Hoyle.

Studies of the electrical properties of semiconductors led to the discovery of the solid state transistor by John Bardeen, Walter Brattain, and William Shockley. Later advancements of this remarkable device revolutionized electronics for the home, industry, and space exploration.

John Mauchly and J. Presper Eckert built the first fully electronic computer, ENIAC. A new mathematical theory of cybernetics---the control and communication of information in machines and animals---involving feedback and other basic concepts was first unified and developed by Norbert Wiener. Society as a whole is still feeling the impact of these inventions.

A website entitled "A History of Computational Chemistry"

A biochemist, James Watson, and a physicist, Francis Crick, combined their knowledge and won the race with other scientists to build the first accurate molecular model of DNA (deoxyribonucleic acid). In their model, four molecular building blocks were arranged in two spiraling chains. Complementary paired units explained how the chains were linked and how DNA copied itself.

Francis Crick speculated that each strand of DNA formed an intermediary genetic code carrier, RNA (ribonucleic acid), which controlled the manufacture of proteins. This idea of a DNA master "blueprint" explained why characteristics acquired during an organism's life cannot be inherited, and gave a molecular mechanism for mutations which fuel evolutionary change.

The symmetry with which we are familiar, like reflections in a mirror, does not necessarily hold for subatomic particles. Instead of the "conservation of parity," an assumed mirror symmetry, Chen Yang and Tsung Lee hypothesized correctly that more electrons are emitted in one direction than another in neutron decay.

Marshall Nirenberg and J. Heinrich Matthaei were the first to demonstrate in a novel cell-free system that particular sequences of three "bases" of RNA were the code for making particular amino acids. The sequence of amino acids, in turn, determines the structure and function of any protein.