Colorado River

The Colorado River is the principal river of the Southwestern United
States and northwest Mexico. Rising in the western Rocky Mountains, the
1,450-mile (2,330 km) river drains a vast arid region of the Colorado
Plateau and the Mojave and Sonoran Deserts as it heads towards the Gulf
of California. Known for its dramatic scenery (Horseshoe Bend pictured)
and its whitewater, the Colorado carves numerous gorges, including the
Grand Canyon in northern Arizona. For 8,000 years, the Colorado Basin
was only sparsely populated by Native Americans, though some of their
ancient civilizations employed advanced irrigation techniques. Even
after becoming part of the U.S. in the 1800s, the Colorado River country
remained extremely remote until John Wesley Powell's 1869 river-running
expedition, which began to open up the river for future development.
Since the completion of Hoover Dam in 1935, the Colorado has been tamed
by an extensive system of dams and canals, providing for irrigation,
cities, and hydropower. Today the Colorado supports 40 million people in
seven U.S. and two Mexican states; with every drop of its water
allocated, it no longer reaches the sea except in years of heavy runoff.

Web search engine

A web search engine is a software system that is desined to search for information on the World Wide Web.The search results are generally presented in 
a line of results often referred to as search engine reults pages (SERPs).The
information may be a mix of web pages,images,and other types of files.Some 
search engines also mine data available in databases or open directories. Unlike 
web directories,which are maintained only by human editors, search engines also
maintain real-time information by running an algorithm on a web crawler.

nebular hypothesis

The nebular hypothesis is the most widely accepted model in cosmogony
explaining the formation and evolution of the Solar System, which
suggests that it formed from nebulous material in space. The hypothesis
offers explanations for some of the Solar System's properties, including
the nearly circular and coplanar orbits of the planets, and their motion
in the same direction as the Sun's rotation. According to the
hypothesis, Sun-like stars form over about 100 million years, in
massive, gravitationally unstable clouds of molecular hydrogen (giant
molecular clouds). Matter coalesces to smaller, denser clumps within,
which then proceed to both rotate and collapse, forming stars. Star
formation produces a gaseous protoplanetary disk around the young star,
which may give birth to planets (protoplanetary disk pictured in the
Orion Nebula). The formation of planetary systems is thought to be a
natural result of star formation, with dense terrestrial planets forming
closer to the star and colder giant planets forming further away, beyond
the so-called frost line. Originally applied only to our own Solar
System, the nebular hypothesis is now thought to be at work throughout
the universe.

Read more: <https://en.wikipedia.org/wiki/Nebular_hypothesis>