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 utilize 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 the brand name of the polymer polytetrafluoroethylene
) discovered by Roy J. Plunkett
(1910–1994) of DuPont
in 1938 and introduced as a commercial product in 1946. It is a fluoropolymer
but not a thermoplastic
in the true sense.
PTFE has the lowest coefficient of friction of any known solid material. It is used as a non-stick coating for pans and other cookware. PTFE is very non-reactive and is often used in containers and pipework for reactive chemicals. Its melting point is 327°C, but its properties degrade above 260°C. At this point gaseous fluorine compounds are released that are dangerous to humans.
Other polymers with similar composition are known by the Teflon name: fluorinated ethylene-propylene (FEP) and perfluoroalkoxy polymer resin (PFA). They retain the useful properties of PTFE of low friction and non-reactivity, but are more easily formable. FEP is softer than PTFE and melts at 260°C; it is highly transparent and resistant to sunlight.
A plasma globe is usually a clear glass orb, filled with a mixture of various inert gases at low pressure, and driven by high frequency alternating current at high voltage (approx. 35 kHz, 2–5 kV,15.7 Krem), generated by a high voltage transformer. A much smaller orb in its centre serves as an electrode. Beams or snakes of "light" (actually emergent patterns in ionized gas) extend from the inner electrode to the outer glass container, giving an appearance similar to multiple constant beams of coloured lightning. The beams first follow the electric field lines of the dipole, but move up due to convection.
(February 15, 1564 – January 8, 1642) was an Italian physicist
, and philosopher
who is closely associated with the scientific revolution
. His achievements include improvements to the telescope
, a variety of astronomical observations, the first
laws of motion, and effective support for Copernicanism
. According to Stephen Hawking
, Galileo has contributed more to the creation of the modern natural sciences than anybody else. He is the "father of modern astronomy
," the "father of modern physics
," and the "father of science
." The work of Galilei is considered to be a significant break from that of Aristotle
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