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.
A mirror neuron
is a neuron
both when an animal performs an action and when the animal observes the same action performed by another (especially conspecific
) animal. Thus, the neuron "mirrors" the behavior of another animal, as though the observer were himself performing the action. These neurons have been observed in primates
and in some birds
. In humans, they have been found in Broca's area
and the inferior parietal cortex
of the brain. Some scientists consider mirror neurons one of the most important findings of neuroscience
in the last decade. See for example, an essay by Ramachandran
on their potential importance in imitation and language.
In humans, mirror neurons are found in the inferior frontal cortex, close to Broca's area, a language region. This has led to suggestions that human language evolved from a gesture performance/understanding system implemented in mirror neurons. However, like many theories of language evolution, there is little direct evidence either way.
Wake turbulence, also known as "jetwash", is turbulence that forms behind an aircraft as it passes through the air. This turbulence can be especially hazardous during the landing and take off phases of flight, where an aircraft's proximity to the ground makes a timely recovery from turbulence-induced problems unlikely. Wingtip vortices make up the primary and most dangerous component of wake turbulence, but normal wake effects are also an important part. A method of reducing wingtip vortices employs the use of winglets.