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 provide explanations of events in 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; along with the changing of "natural philosophy" to "natural science."
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 system that uses radio
waves to determine and map the location, direction, and/or speed of both moving and fixed objects such as aircraft
, motor vehicles, weather formations and terrain. A transmitter
emits radio waves, which are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very weak, radio signals can easily be amplified, so radar can detect objects at ranges where other emissions, such as sound
or visible light
, would be too weak to detect. Radar is used in many contexts, including meteorological
detection of precipitation
, air traffic control
detection of speeding traffic
, and by the military.
The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. This acronym of American origin replaced the previously used British abbreviation RDF (Radio Direction Finding). The term has since entered the English language as a standard word, radar, losing the capitalization in the process.
An 18th Century Persian astrolabe used for determining the time at both day and night. The points of the curved spikes on the front rete plate mark the positions of the brightest stars, the name of each star being labeled at the base of each spike. The back plate, or mater, is engraved with projected coordinate lines. From the Whipple Museum of the History of Science collection.
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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