he renewal of learning in Europe, that began with 12th century 

Scholasticism, came to an end about the time of

the Black Death, and the initial period of the subsequent Italian Renaissance is sometimes seen as a lull in
scientific activity. The Northern Renaissance, on the other hand, showed a decisive shift in focus from
Aristoteleian natural philosophy to chemistry and the biological sciences (botany, anatomy, and medicine).
Thus modern science in Europe was resumed in a period of great upheaval: the Protestant Reformation
and Catholic Counter-Reformation; the discovery of the Americas by Christopher Columbus; the Fall of
Constantinople; but also the re-discovery of Aristotle during the Scholastic period presaged large social and
political changes. Thus, a suitable environment was created in which it became possible to question scientific
doctrine, in much the same way that Martin Luther and John Calvin questioned religious doctrine. The works
of Ptolemy (astronomy), Galen (medicine), and Aristotle (physics) were found not always to match everyday
observations. For example, an arrow flying through the air after leaving a bow contradicts Aristotle's laws of
motion, which say that a moving object must be constantly under influence of an external force, as the natural
state of earthly objects is to be at rest. Work by Vesalius on human cadavers also found problems with the
Galenic view of anatomy.

Vesalius' experiments inspired interest in human anatomy.

The willingness to question previously held truths and search for new answers resulted in a period of major
scientific advancements, now known as the Scientific Revolution. The Scientific Revolution is traditionally held
by most historians to have begun in 1543, when De Revolutionibus, by the astronomer Nicolaus Copernicus,
was first printed. The thesis of this book was that the Earth moved around the Sun. The period culminated with
the publication of the Philosophiae Naturalis Principia Mathematica in 1687 by Isaac Newton.

Other significant scientific advances were made during this time by Galileo Galilei, Edmond Halley, Robert
Hooke, Christiaan Huygens, Tycho Brahe, Johannes Kepler, Gottfried Leibniz, and Blaise Pascal. In
philosophy, major contributions were made by Francis Bacon, Sir Thomas Browne, René Descartes,
and Thomas Hobbes. The basics of scientific method were also developed: the new way of thinking
emphasized experimentation and reason over traditional considerations.

Modern science
Albert Einstein

The Scientific Revolution established science as the preeminent source for the growth of knowledge. During
the 19th century, the practice of science became professionalized and institutionalized in ways which would
continue through the 20th century, as the role of scientific knowledge grew and became incorporated with many
aspects of the functioning of nation-states.

Natural sciences
Physics

The Scientific Revolution is a convenient boundary between ancient thought and classical
physics. Nicolaus Copernicus revived the heliocentric model of the solar system first devised
by Aristarchus of Samos. This was followed by the first known model of planetary motion given
by Kepler in the early 17th century, which proposed that the planets follow elliptical orbits, with the Sun at
one focus of the ellipse. Also, Galileo pioneered the use of experiment to validate physical theories, a key
idea in scientific method.

James Clerk Maxwell

In 1687, Isaac Newton published the Principia Mathematica, detailing two comprehensive and successful

physical theories: Newton's laws of motion, which lead to classical mechanics; and Newton's Law of
Gravitation, which describes the fundamental force of gravity. The behaviour of electricity and magnetism
was studied by Faraday, Ohm, and others during the early 19th century. These studies led to the
unification of the two phenomena into a single theory of electromagnetism, by Maxwell (known
as Maxwell's equations).

Diagram of the expanding universe

The beginning of the 20th century brought the start of a revolution in physics. The long-held theories of
Newton were shown not to be correct in all circumstances. Beginning in 1900, Max Planck, Albert
Einstein, Niels Bohr and others developed quantum theories to explain various anomalous experimental
results, by introducing discrete energy levels. Not only did quantum mechanics show that the laws of
motion did not hold on small scales, but even more disturbingly, the theory of general relativity, proposed
by Einstein in 1915, showed that the fixed background of spacetime, on which both Newtonian mechanics
and special relativity depended, could not exist. In 1925, Werner Heisenberg and Erwin Schrödinger
formulated quantum mechanics, which explained the preceding quantum theories. The observation
by Edwin Hubble in 1929 that the speed at which galaxies recede positively correlates with their distance,
led to the understanding that the universe is expanding, and the formulation of the Big Bang theory
by George Gamow.

The development of the atomic bomb ushered in the era of " Big Science" in physics.

Further developments took place during World War II, which led to the practical application of radar and
the development and use of the atomic bomb. Though the process had begun with the invention of
the cyclotron by Ernest O. Lawrence in the 1930s, physics in the postwar period entered into a phase of
what historians have called " Big Science", requiring massive machines, budgets, and laboratories in
order to test their theories and move into new frontiers. The primary patron of physics became state
governments, who recognized that the support of "basic" research could often lead to technologies useful
to both military and industrial applications. Currently, general relativity and quantum mechanics are
inconsistent with each other, and efforts are underway to unify the two.
Chemistry

Linus Pauling

The history of modern chemistry can be taken to begin with the distinction of chemistry
from alchemy by Robert Boyle in his work The Sceptical Chymist, in 1661 (although the alchemical
tradition continued for some time after this) and the gravimetric experimental practices of medical
chemists like William Cullen, Joseph Black, Torbern Bergman and Pierre Macquer. It can also be
dated Antoine Lavoisier's naming of oxygen and the law of conservation of mass, which
refuted phlogiston theory. Proof that all matter is made of atoms, which are the smallest
constituents of matter that cannot be broken down without losing the basic chemical and physical
properties of that matter, was provided by John Dalton in 1803. He also formulated the law of mass
relationships. In 1869, Dmitri Mendeleev composed his periodic table of elements on the basis of
Dalton's discoveries.

The synthesis of urea by Friedrich Wöhler opened a new research field, organic chemistry, and by
the end of the 19th century, scientists were able to synthesize hundreds of organic compounds. The
later part of the nineteenth century saw the exploitation of the Earth's petrochemicals, after the
exhaustion of the oil supply from whaling. By the twentieth century, systematic production of refined
materials provided a ready supply of products which provided not only energy, but also synthetic
materials for clothing, medicine, and everyday disposable resources. Application of the techniques
of organic chemistry to living organisms resulted in physiological chemistry, the precursor
to biochemistry. The twentieth century also saw the integration of physics and chemistry, with
chemical properties explained as the result of the electronic structure of the atom. Linus Pauling's
book on The Nature of the Chemical Bond used the principles of quantum mechanics to
deduce bond angles in ever-more complicated molecules. Pauling's work culminated in the physical
modelling of DNA, the secret of life (in the words of Francis Crick, 1953). In the same year,
the Miller-Urey experiment demonstrated in a simulation of primordial processes, that basic
constituents of proteins, simple amino acids, could themselves be built up from simpler molecules.
Geology

Geology existed a cloud of isolated, disconnected ideas about rocks, minerals, and landforms
long before it became a coherent science. Theophrastus' work on rocks Peri lithōn remained
authoritative for millennia: its interpretation of fossils was not overturned until after the
Scientific Revolution. Chinese polymath Shen Kua (1031 - 1095) was the first to formulate
hypotheses for the process of land formation. Based on his observation of fossils in a
geological stratum in a mountain hundreds of miles from the ocean, he deduced that the land
was formed by erosion of the mountains and by deposition of silt.

Plate tectonics - seafloor spreading and continental drift illustrated on relief globe

Geology was not systematically restructured during the Scientific Revolution, but individual
theorists made important contributions. Robert Hooke, for example, formulated theory of
earthquakes, and Nicholas Steno developed the theory of superposition and argued
that fossils were the remains of once-living creatures. Beginning with Thomas Burnet's Sacred
Theory of the Earth in 1685, natural philosophers began to explore the idea that the Earth had
changed over time. Burnet and his contemporaries interpreted Earth's past in terms of events
described in the Bible, but their work laid the intellectual foundations for lsecular
interpretations of Earth history.

Modern geology, like modern chemistry, gradually evolved during the 1700s and early
1800s. Benoit de Maillet and the Comte de Buffon argued that Earth was much older than the
6,000 years envisioned by biblical scholars. Jean-Etienne Guettard and Nicolas Desmarest
hiked central France and recorded their observations on some of the first geological
maps. Abraham Werner created a systemtic classifaction scheme for rocks and minerals--an
achievement as significant for geology as that of Linnaeus was for biology. Werner also
proposed a generalized interpretation of Earth history, as did contemporary Scottish
polymath James Hutton. Georges Cuvier and Alexandre Brongniart, expanding on the work
of Steno, argued that layers of rock could be dated by the fossils they contained: a principle
first applied to the geology of the Paris Basin. The use of index fossils became a powerful tool
for making geological maps, because it allowed geologists to correlate the rocks in one
locality with those of similar age in other, distant localities. Over the first half of the nineteenth
century, geologists such as Charles Lyell, Adam Sedgwick, and Roderick Murchison applied
the new technique to rocks throughout Europe and eastern North America, setting the stage
for more detailed, government-funded mapping projects in later decades.

Midway through the 19th century, the focus of geology shifted from description and
classification to attempts to understand how the surface of the Earth changed. The first
comprehensive theories of mountain building were proposed during this period, as were the
first modern theories of earthquakes and volcanoes. Louis Agassiz and others established the
reality of continent-covering ice ages, and "fluvialists" like Andrew Crombie Ramsay argued
that river valleys were formed, over millions of years by the rivers that flow through
them. Abraham Wegener's theory of "continental drift" was widely dismissed when it was
proposed in the 1910s, but new data gathered in the 1950s and 1960s led to the theory
of plate tectonics, which provided a plausible mechanism for it. Plate tectonics also provided a
unified explanation for a wide range of seemingly unrelated geological phenomena. Since
1970 it has been the unifying principle in geology.

Geologists' embrace of plate tectonics was part of a broadening of the field from a study of
rocks into a study of the Earth as a planet. Other elements of this transformation include:
geophysical studies of the interior of the Earth, the grouping of geology
with meteorology and oceanography as one of the "earth sciences," and comparisons of Earth
and the solar system's other rocky planets.
Astronomy

Advances in astronomy and in optical systems in the 19th century resulted in the first
observation of an asteroid (1 Ceres) in 1801, and the discovery of Neptune in 1846.

George Gamow, Ralph Alpher, and Robert Hermann had calculated that there should be
evidence for a Big Bang in the background temperature of the universe. In 1964, Arno
Penzias and Robert Wilson discovered a 3 kelvin background hiss in their Bell
Labs radiotelescope, which was evidence for this hypothesis, and formed the basis for a
number of results that helped determine the age of the universe.

Supernova SN1987A was observed by astronomers on Earth both visually, and in a

triumph for neutrino astronomy, by the solar neutrino detectors at Kamiokande. But the
solar neutrino flux was a fraction of its theoretically-expected value. This discrepancy
forced a change in some values in the standard model for particle physics.
Biology, medicine, and genetics

Semi-conservative DNA replication

In 1847, Hungarian physician Ignác Fülöp Semmelweis dramatically reduced the

occurrency of puerperal fever by the simple experiment of requiring physicians to
wash their hands before attending to women in childbirth. This discovery predated
the germ theory of disease. However, Semmelweis' findings were not appreciated
by his contemporaries and came into use only with discoveries by British
surgeon Joseph Lister, who in 1865 proved the principles of antisepsis. Lister's
work was based on the important findings by French biologist Louis Pasteur.
Pasteur was able to link microorganisms with disease, revolutionizing medicine.
He also devised one of the most important methods in preventive medicine, when
in 1880 he produced a vaccine against rabies. Pasteur invented the process
of pasteurization, to help prevent the spread of disease through milk and other
foods.
Perhaps the most prominent and far-reaching theory in all of science has been the
theory of evolution by natural selection put forward by the British naturalist Charles
Darwin in his On the Origin of Species in 1859. Darwin's theory proposed that all
differences in animals were formed by natural processes over long periods of time,
and that even humans were simply evolved organisms. Implications of evolution
on fields outside of pure science have led to both opposition and support from
different parts of society, and profoundly influenced the popular understanding of
"man's place in the universe". In the early 20th century, the study of heredity
became a major investigation after the rediscovery in 1900 of the laws of
inheritance developed by the Austrian monk Gregor Mendel in 1866. Mendel's
laws provided the beginnings of the study of genetics, which became a major field
of research for both scientific and industrial research. By 1953, James Watson
and Francis Crick clarified the basic structure of DNA, the genetic material for
expressing life in all its forms. In the late 20th century, the possibilities of genetic
engineering became practical for the first time, and a massive international effort
began in 1990 to map out an entire human genome (the Human Genome Project)
has been touted as potentially having large medical benefits.
Ecology

Earthrise over the Moon, Apollo 8, NASA. This image helped create awareness of the
finiteness of Earth, and the limits of its natural resources.

The discipline of ecology typically traces its origin to the synthesis

of Darwinian evolution and Humboldtian biogeography, in the late 19th and
early 20th centuries. Equally important in the rise of ecology, however,
were microbiology and soil science—particularly the cycle of life concept,
prominent in the work Louis Pasteur and Ferdinand Cohn. The
word ecology was coined by Ernst Haeckel, whose particularly holistic view
of nature in general (and Darwin's theory in particular) was important in the
spread of ecological thinking. In the 1930's, Arthur Tansley and others began
developing the field of ecosystem ecology, which combined experimental soil
science with physiological concepts of energy and the techniques of field
biology. The history of ecology in the 20th century is closely tied to that
of environmentalism; the Gaia hypothesis in the 1960s and more recently the
scientific-religious movement of Deep Ecology have brought the two closer
together.

Social sciences