User:NatureA16/3 (2007)
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May to June 2007
The featured things
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[edit] Global Warming
April 30 - May 6
Global warming is the increase in the average temperature of the Earth's atmosphere and oceans that has been observed in recent decades. The scientific opinion on climate change is that much of the recent change may be attributed to human activities. Carbon dioxide and other greenhouse gases released by the burning of fossil fuels, land clearing, agriculture, among other human activities, are the primary sources of the human-induced component of warming. Observational sensitivity studies and climate models referenced by the IPCC predict that global temperatures may increase by between 1.4 and 5.8 °C between 1990 and 2100. An increase in global temperatures can in turn cause other changes, including rises in sea level and changes in the amount and pattern of precipitation. These changes may increase the frequency and intensity of extreme weather events, such as tropical cyclones or floods. There are a few scientists who contest the view about attribution of recent warming to human activity. Uncertainties exist regarding how much climate change should be expected in the future, and there is a hotly contested political and public debate over attempts to reduce or reverse future warming, and how to cope with possible consequences.
Recently featured: Buddhism: Sense of Reason - Orca - Velociraptor
[edit] Galaxy
May 7 - May 13
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A galaxy is a massive, gravitationally bound system that consists of stars, an interstellar medium of gas and dust, and dark matter. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (1012) stars, all orbiting a common center of gravity. Galaxies can also contain a large number of multiple star systems and star clusters as well as various types of interstellar clouds. Historically, galaxies have been categorized according to their apparent shape. Interactions between nearby galaxies, which may ultimately result in a galaxy merger, may induce episodes of significantly increased star formation, producing what is called a starburst galaxy. There are probably more than a hundred billion (1011) galaxies in the observable universe. Most galaxies are a thousand to a hundred thousand parsecs in diameter and are usually separated from one another by distances on the order of millions of parsecs. Intergalactic space, the space between galaxies, is filled with a tenuous gas with an average density less than one atom per cubic metre. There is some evidence that supermassive black holes may exist at the center of many, if not all, galaxies. These massive objects are believed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least one such object within its nucleus.
Recently featured: Global warming - Buddhism: Sense of Reason - Orca
[edit] Uranium
May 14 - May 20
Uranium is a silvery metallic chemical element that has atomic number 92 in the actinide series of the periodic table. The heaviest naturally occurring element, uranium is nearly twice as dense as lead and weakly radioactive. It occurs naturally in low concentrations in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite. In nature, uranium atoms exist as uranium-238 (99.275%), uranium-235 (0.72%), and a very small amount of uranium-234 (0.0058%). Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.5 billion years and that of uranium-235 is 700 million years, making them useful in dating the age of the earth. Along with thorium and plutonium, it is one of the three fissile elements, meaning it can easily break apart to become lighter elements. This property of uranium-235 and to a lesser degree uranium-233 generates the heat needed to run nuclear reactors and provides the explosive material for nuclear weapons. Both uses rely on the ability of uranium to produce a sustained nuclear chain reaction. Depleted uranium (uranium-238) is used in kinetic energy penetrators and armor plating.
Recently featured: Galaxy - Global warming - Buddhism: Sense of Reason
[edit] Cane Toad
May 21 - May 27
The Cane Toad is a large, terrestrial true toad native to Central and South America. It is a member of the genus Bufo, which includes hundreds of different true toad species in different habitats throughout the world. The Cane Toad is a prolific breeder; females lay single-clump spawns with large numbers of eggs. Its reproductive success is partly due to opportunistic feeding: it has a diet, unusual among frogs, of both dead and living matter. Adults average 10 to 15 centimetres (4–6 in) in length, the largest recorded specimen weighed 2.65 kilograms (5.84 lb) and measured 38 centimetres (15 in) from snout to vent. The Cane Toad has large poison glands, and adults and tadpoles are highly toxic to most animals if ingested. Because of its voracious appetite, the Cane Toad has been introduced to many regions of the Pacific as a method of agricultural pest control, notably in the case of Australia in 1935, and derives its common name from its use against sugar cane pests. The Cane Toad is considered a pest in many of its introduced regions, as its toxic skin kills many native predators when ingested.
Recently featured: Uranium - Galaxy - Global warming
[edit] Solar eclipse
May 28 - June 3
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring Earth's view of the Sun totally or partially. This configuration can only occur at the New Moon phase, when the Sun and Moon are in conjunction, as seen from Earth. In ancient times, and in some countries today, solar eclipses are attributed mythical properties. Total solar eclipses are very rare events for a given place on Earth. This is because totality is only visible where the umbra of the Moon touches the Earth's surface. Some people travel to the most remote places imaginable to observe eclipses. A total solar eclipse is considered by them to be the most spectacular natural phenomenon that one can observe. The 1999 total eclipse in Europe, which was without doubt the most watched eclipse in human history, helped to increase public awareness of the phenomenon. This was illustrated by many people willing to make the journey to witness the 2005 annular eclipse and the 2006 total eclipse. The next total solar eclipse will be the Solar eclipse of August 1, 2008.
Recently featured: Cane toad - Uranium - Galaxy
[edit] Comet Shoemaker-Levy 9
June 4 - June 10
Comet Shoemaker-Levy 9 was discovered in a photograph taken on the night of March 24, 1993 with the Schmidt telescope at the Mount Palomar Observatory in California, and was the ninth comet discovered by astronomers Carolyn and Eugene M. Shoemaker and David Levy. It turned out to be the first comet observed orbiting a planet (Jupiter, in this case) and not the Sun. The comet was also unusual because it was in fragments, due to a close encounter with Jupiter in July 1992 when it approached closer to the planet than its Roche limit and was pulled apart by tidal forces. Between July 16 and July 22, 1994, the fragments of the comet collided with Jupiter's southern hemisphere at 60 kilometres per second (37 miles per second), providing the first direct observation of the collision of two solar system objects. The collision resulted in disruptions in Jupiter's atmosphere, such as plumes and bubbles of gas, and dark spots in the atmosphere which remained visible for several months. The event was closely observed and recorded by astronomers worldwide as a result of its tremendous scientific importance, and also generated a large amount of coverage in the popular media.
Recently featured: Solar eclipse - Cane toad - Uranium
[edit] Bacteria
June 11 - June 17
Bacteria are unicellular microorganisms. They are typically a few micrometres long and have many different shapes including spheres, rods and spirals. The study of bacteria is bacteriology, a branch of microbiology. Bacteria are ubiquitous, living in every possible habitat on the planet including soil, underwater, deep in the earth's crust and even such environments as acidic hot springs and radioactive waste. In all, there are around five nonillion (5 × 1030) bacteria in the world. There are 10 times more bacterial cells than human cells in the human body, with large numbers of bacteria on the skin and in the digestive tract. Although the vast majority of these bacteria are harmless or beneficial, a few pathogenic bacteria cause infectious diseases, including cholera, syphilis, anthrax, leprosy and bubonic plague. The most common fatal bacterial disease is tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Bacteria are prokaryotes and, unlike animals and other eukaryotes, bacterial cells do not contain a nucleus or other membrane-bound organelles. Although the term bacteria has traditionally been generally applied to all prokaryotes, the scientific nomenclature changed after the discovery that prokaryotic life consists of two very different groups of organisms that evolved independently from an ancient common ancestor.
Recently featured: Comet Shoemaker-Levy 9 - Solar eclipse - Cane toad
[edit] India
June 18 - June 24
India is a large multicultural country in South Asia, with a population of over one billion. The Indian economy is the fourth largest in the world in terms of purchasing power parity and is the world's second-fastest growing economy. India is also the second most populous country in the world, and the world's largest democracy. India has grown significantly, in terms of both population and strategic importance, in the last 20 years. It has also emerged as an important regional power, with one of the world's largest militaries and a declared nuclear weapons capability. Strategically located in Asia, constituting most of the Indian subcontinent, India straddles many busy trade routes. It shares its borders with Pakistan, the People's Republic of China, Myanmar, Bangladesh, Nepal, Bhutan and Afghanistan. Sri Lanka, the Maldives and Indonesia are the nearby island nations in the Indian Ocean. Home to some of the most ancient civilizations in the world, India was formally ruled by the British for almost 90 years before gaining independence in 1947.
Recently featured: Bacteria - Comet Shoemaker-Levy 9 - Solar eclipse
[edit] Homo floresiensis
June 25 - July 1
Homo floresiensis is a newly described species in the genus Homo, remarkable for its small body, small brain, and recent survival. It is thought to have been contemporaneous with modern humans on the remote Indonesian island of Flores. One sub-fossil skeleton, dated at 18,000 years old, is largely complete except for arm bones which may yet be found. It was discovered in deposits in Liang Bua Cave, Flores, in 2003. Also here, parts of six other individuals, all diminutive, have been recovered as well as similarly small stone tools from horizons ranging from 94,000 to 13,000 years ago. The discoverers have called members of the diminutive species hobbits, after J.R.R. Tolkien's fictional race of roughly the same height. In the island's mythology there were common references to Ebu Gogo, a small furry man, even into the 19th century.
Recently featured: India - Bacteria - Comet Shoemaker-Levy 9
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