Rare earth

Rare earth may refer to:

Rare earth element

A rare earth element (REE) or rare earth metal (REM), as defined by IUPAC, is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Scandium and yttrium are considered rare earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties.

Despite their name, rare earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, or as abundant as copper. They are not especially rare, but they tend to occur together in nature and are difficult to separate from one another. (The word "rare" is an archaic word for "difficult".) However, because of their geochemical properties, rare earth elements are typically dispersed and not often found concentrated as rare earth minerals in economically exploitable ore deposits. It was the very scarcity of these minerals (previously called "earths") that led to the term "rare earth". The first such mineral discovered was gadolinite, a mineral composed of cerium, yttrium, iron, silicon and other elements. This mineral was extracted from a mine in the village of Ytterby in Sweden; four of the rare earth elements bear names derived from this single location.

Rare Earth (book)

Rare Earth: Why Complex Life Is Uncommon in the Universe is a 2000 popular science book about xenobiology by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist, both faculty members at the University of Washington. The book is the origin of the term 'Rare Earth Hypothesis' which, like the book, asserts the concept that complex life is rare in the universe.

Synopsis

The book argues that the universe is fundamentally hostile to complex life and that while microbial life may be common in the universe, complex intelligent life (like the evolution of biological complexity from simple life on Earth) required an exceptionally unlikely set of circumstances, and therefore complex life is likely to be extremely rare. The book argues that among the essential criteria for life are a terrestrial planet with plate tectonics and oxygen, a large moon, magnetic field, a gas giant like Jupiter for protection and an orbit in the habitable zone of the right kind of star.

Baotou

Baotou (Mongolian: ᠪᠤᠭᠤᠲᠤ ᠬᠣᠲᠠ Buɣutu qota; Chinese: 包头市) also known as Bugthot is the largest industrial city in the Inner Mongolia Autonomous Region of northern China. Governed as a prefecture-level city, its built-up (or metro) area made up of 5 urban districts is home to 2,070,801 inhabitants with a total population of over 2.65 million accounting for counties under its jurisdiction. The city's Mongolian name means "place with deer", and an alternate name is "Lucheng" (鹿城; Lùchéng), meaning "Deer City". The 39,000 capacity Baotou Olympic Sports Centre Stadium is the main sports venue in the city, used mostly for association football games.

Administrative divisions

Baotou is divided into 10 county-level divisions, including 7 districts, 1 county and 2 banners.

History

The area now known as Baotou was inhabited since ancient times by nomads, most notably the Mongols. Near the end of the Han Dynasty, Lü Bu, a particularly noteworthy warrior, was born in today's Jiuyuan District of Baotou. Compared to the capital, Hohhot, Baotou's construction as a city came relatively late, being incorporated as a town in 1809. The city's site was chosen because it was in an arable region of the Yellow River's Great Bend.