Science (from the Latin word scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
The earliest roots of science can be traced to Ancient Egypt and Mesopotamia in around 3500 to 3000 BCE. Their contributions to mathematics, astronomy, and medicine entered and shaped Greek natural philosophy of classical antiquity, whereby formal attempts were made to explain events of the physical world based on natural causes. After the fall of the Western Roman Empire, knowledge of Greek conceptions of the world deteriorated in Western Europe during the early centuries (400 to 1000 CE) of the Middle Ages but was preserved in the Muslim world during the Islamic Golden Age. The recovery and assimilation of Greek works and Islamic inquiries into Western Europe from the 10th to 13th century revived natural philosophy, which was later transformed by the Scientific Revolution that began in the 16th century as new ideas and discoveries departed from previous Greek conceptions and traditions. The scientific method soon played a greater role in knowledge creation and it was not until the 19th century that many of the institutional and professional features of science began to take shape.
Modern science is typically divided into three major branches that consist of the natural sciences (e.g., biology, chemistry, and physics), which study nature in the broadest sense; the social sciences (e.g., economics, psychology, and sociology), which study individuals and societies; and the formal sciences (e.g., logic, mathematics, and theoretical computer science), which study abstract concepts. There is disagreement, however, on whether the formal sciences actually constitute a science as they do not rely on empirical evidence. Disciplines that use existing scientific knowledge for practical purposes, such as engineering and medicine, are described as applied sciences.
Science is based on research, which is commonly conducted in academic and research institutions as well as in government agencies and companies. The practical impact of scientific research has led to the emergence of science policies that seek to influence the scientific enterprise by prioritizing the development of commercial products, armaments, health care, and environmental protection.
is a change in the genetic
makeup of a population within a species
. Since the emergence of modern genetics
in the 1940s
, evolution has been defined more specifically as a change in the frequency of alleles
from one generation to the next. The word "evolution" is often used as a shorthand for the modern theory
of evolution of species
based upon Charles Darwin
's theory of natural selection
, which states that all modern species are the products of an extensive process that began over three billion years ago with simple single-celled organisms
, and Gregor Mendel
's theory of genetics
. As the theory of evolution by natural selection and genetics has become universally accepted in the scientific community, it has replaced other explanations including creationism
. Skeptics, often creationists, sometimes deride evolution as "just a theory" in an attempt to characterize it as an arbitrary choice and degrade its claims to truth. Such criticism overlooks the scientifically
-accepted use of the word "theory" to mean a falsifiable
and well-supported hypothesis
The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble for his discovery of galaxies outside the Milky Way and his creation of Hubble's Law, which calculates the rate at which the universe is expanding. Its position outside the Earth's atmosphere allows it to take sharp optical images of very faint objects, and since its launch in 1990, it has become one of the most important instruments in the history of astronomy. It has been responsible for many ground-breaking observations and has helped astronomers achieve a better understanding of many fundamental problems in astrophysics. Hubble's Ultra Deep Field is the deepest (most sensitive) astronomical optical image ever taken.
Isaac Newton, English physicist
. A man of profound genius
, he is widely regarded as the most influential scientist in history. He is associated with the scientific revolution
and the advancement of heliocentrism
. Among his scientific accomplishments, Newton wrote the Philosophiae Naturalis Principia Mathematica
, wherein he described universal gravitation
and, via his laws of motion
, laid the groundwork for classical mechanics
. With Gottfried Wilhelm Leibniz
he is credited for the development of differential calculus
. Newton was the first to promulgate a set of natural laws that could govern both terrestrial
motion and celestial motion
, and is credited with providing mathematical substantiation for Kepler's laws of planetary motion
, which he expanded by arguing that orbits
(such as those of comets
) could include all conic sections (such as the ellipse
, and parabola
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