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.
The geology of the Grand Canyon area
exposes one of the most complete sequences of rock
anywhere, representing a period of nearly 2 billion years of the Earth
's history in that part of North America
. The major sedimentary rock
layers exposed in the Grand Canyon
and in the Grand Canyon National Park
area range in age from 200 million to nearly 2 billion years old. Most were deposited in warm, shallow seas
and near ancient, long-gone sea shores. Both marine and terrestrial sediments are represented, including fossilized sand dunes
from an extinct desert
Uplift of the region started about 75 million years ago in the Laramide orogeny, a mountain-building event that is largely responsible for creating the Rocky Mountains to the east. Accelerated uplift started 17 million years ago when the Colorado Plateaus (on which the area is located) were being formed. In total these layers were uplifted an estimated 10,000 feet (3000 m) which enabled the ancestral Colorado River to cut its channel into the four plateaus that constitute this area. But the canyon did not start to form until 5.3 million years ago when the Gulf of California opened up and thus lowered the river's base level (its lowest point) from that of large inland lakes to sea level.
Lightning is a powerful natural electrostatic discharge of lighted streaks produced during a thunderstorm. This abrupt electric discharge is accompanied by the emission of visible light and other forms of electromagnetic radiation. The electric current passing through the discharge channels rapidly heats and expands the air into plasma, producing acoustic shock waves (thunder) in the atmosphere.