Creation

Many cultures have stories describing the origin of the world, which may be roughly grouped into common types. In one type of story, the world is born from a world egg; such stories include the Finnish epic poem Kalevala, the Chinese story of Pangu or the Indian Brahmanda Purana. In related stories, the Universe is created by a single entity emanating or producing something by him- or herself, as in the Tibetan Buddhism concept of Adi-Buddha, the ancient Greek story of Gaia (Mother Earth), the Aztec goddess Coatlicue myth, the ancient Egyptian god Atum story, or the Genesis creation narrative. In another type of story, the Universe is created from the union of male and female deities, as in the Maori story of Rangi and Papa. In other stories, the Universe is created by crafting it from pre-existing materials, such as the corpse of a dead god — as from Tiamat in the Babylonian epic Enuma Elish or from the giant Ymir in Norse mythology – or from chaotic materials, as in Izanagi and Izanami in Japanese mythology. In other stories, the Universe emanates from fundamental principles, such as Brahman and Prakrti, the creation myth of the Serers, or the yin and yang of the Tao.

Galaxies

Galaxies are sprawling space systems composed of dust, gas, and countless stars. The number of galaxies cannot be counted—the observable universe alone may contain 100 billion. Some of these distant systems are similar to our own Milky Way galaxy, while others are quite different. Galaxies with less than a billion stars are considered "small galaxies." In our own galaxy, the sun is just one of about 100 billion stars. Galaxies are classified into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies. Spiral galaxies, such as the Milky Way, consist of a flat disk with a bulging center and surrounding spiral arms. The galaxy's disk includes stars, planets, dust, and gas—all of which rotate around the galactic center in a regular manner. This spinning motion, at speeds of hundreds of kilometers per second, may cause matter in the disk to take on a distinctive spiral shape like a cosmic pinwheel. Some spiral galaxies obtain even more interesting shapes that earn them descriptive names, such as sombrero galaxies. Older stars reside in the bulge at the center of the galactic disk. Many new stars also form in spiral systems, and their disks are surrounded by a halo, which scientists believe is rich with mysterious dark matter. Elliptical galaxies are shaped as their name suggests. They are generally round but stretch longer along one axis than along the other. They may be nearly circular or so elongated that they take on a cigarlike appearance. Elliptical galaxies contain many older stars, up to one trillion, but little dust and other interstellar matter. Their stars orbit the galactic center, like those in the disks of spiral galaxies, but they do so in more random directions. Few new stars are known to form in elliptical galaxies. The universe's largest known galaxies are giant elliptical galaxies, which may be as much as two million light-years long. Elliptical galaxies may also be small, in which case they are dubbed dwarf elliptical galaxies. Galaxies that are not spiral or elliptical are called irregular galaxies. Irregular galaxies appear misshapen and lack a distinct form, often because they are within the gravitational influence of other galaxies close by. Galactic Mergers Some galaxies occur alone or in pairs, but they are more often parts of larger associations known as groups, clusters, and superclusters. Galaxies in such groups often interact and even merge together in a dynamic cosmic dance of interacting gravity. Mergers cause gases to flow towards the galactic center, which can trigger phenomena like rapid star formation. Our own Milky Way may someday merge with the Andromeda galaxy—just two million light-years away and visible to the naked eye from Earth's Northern Hemisphere. These intergalactic processes may be part of natural evolution by which irregular galaxies transform into one of the other shapes, and by which spiral galaxies eventually become elliptical galaxies—as scientists believe they must. Galaxy Origins Most astronomers suggest that galaxies formed shortly after a cosmic "big bang" that began the universe some 10 billion to 20 billion years ago. In the milliseconds following this explosion, clouds of gases began to coalesce, collapse, and compress under gravity to form the building blocks of galaxies. Scientists are divided on just how galaxies first formed. Some believe that smaller clusters of about one million stars, known as globular clusters, formed first and later gathered into galaxies. Others believe that galaxies formed first and that only later did the stars within them begin to gather into smaller clusters.

The outer space

Outer space, or simply space, is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust and cosmic rays. The baseline temperature, as set by the background radiation (from the theorized Big Bang), is 2.7 kelvin. Plasma with a density of less than one hydrogen atom per cubic meter and a temperature of millions of kelvin in the space between galaxies accounts for most of the baryonic matter in outer space; local concentrations have condensed into stars and galaxies. In most galaxies, observations provide evidence that 90% of the mass is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Data indicates that the majority of the mass-energy in the observable Universe is a poorly understood vacuum energy of space which astronomers label dark energy. Intergalactic space takes up most of the volume of the Universe, but even galaxies and star systems consist almost entirely of empty space. There is no firm boundary where space begins. However the Kármán line, at an altitude of 100 km (62 mi) above sea level, is conventionally used as the start of outer space in space treaties and for aerospace records keeping. The framework for international space law was established by the Outer Space Treaty, which was passed by the United Nations in 1967. This treaty precludes any claims of national sovereignty and permits all states to freely explore outer space. In 1979, the Moon Treaty made the surfaces of objects such as planets, as well as the orbital space around these bodies, the jurisdiction of the international community. Despite the drafting of UN resolutions for the peaceful uses of outer space, anti-satellite weapons have been tested in Earth orbit. Humans began the physical exploration of space during the 20th century with the advent of high-altitude balloon flights, followed by manned rocket launches. Earth orbit was first achieved by Yuri Gagarin of the Soviet Union in 1961 and unmanned spacecraft have since reached all of the known planets in the Solar System. Unfortunately, due to the high cost of getting into space, manned spaceflight has been limited to low Earth orbit and the Moon. In August 2012, Voyager 1 became the first man-made satellite to enter interstellar space. Outer space represents a challenging environment for human exploration because of the dual hazards of vacuum and radiation. Microgravity also has a negative effect on human physiology that causes both muscle atrophy and bone loss. In addition to solving all of these health and environmental issues, humans will also need to find a way to significantly reduce the cost of getting into space if they want to become a space faring civilization. Proposed concepts for doing this are Non-rocket spacelaunch, Skyhooks, and Space elevators.

Solar system

For millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named these planets, meaning wanderers. Mercury, Venus, Mars, Jupiter and Saturn were known in antiquity, and the invention of the telescope added the asteroid belt, Uranus and Neptune, Pluto and many of these worlds' moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today. The discovery of Eris kicked off a rash of new discoveries of dwarf planets, and more than 100 could remain to be found. Trans-Neptunian Region Astronomers had long suspected that a band of icy material known as the Kuiper belt existed past the orbit of Neptune extending from about 30 to 55 times the distance of Earth to the sun, and from the last decade of the 20th century up to now, they have found more than a thousand of such objects. Scientists estimate the Kuiper belt is likely home to hundreds of thousands of icy bodies larger than 60 miles (100 km) wide, as well as an estimated trillion or more comets. Well past the Kuiper belt is the Oort cloud, which theoretically extends from 5,000 to 100,000 times the distance of Earth to the sun, and is home to up to two trillion icy bodies. Past that is the very edge of the solar system, the heliosphere, a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun. Many astronomers think that the limit of the heliosphere, known as the heliopause, is about 9 billion miles (15 billion kilometers) from the sun. Pluto is now considered a dwarf planet dwelling in the Kuiper belt. It is not alone — recent additions include Makemake, Haumea and Eris. Another object dubbed Sedna, which is about three-fourths the size of Pluto, might be the first dwarf planet discovered in the Oort cloud.

The first huge scouter

The Hubble Space Telescope was designed to free astronomers of a limitation that has plagued them since the days of Galileo—Earth's atmosphere. Shifting air pockets in the atmosphere block and distort light, limiting the view from even the most powerful Earth-bound instruments. Orbital telescopes function as eyes in the sky that allow astronomers to peer farther into the universe and see the cosmos more clearly. Scientists began dreaming of such a telescope in the 1940s, but it took more than four decades for those dreams to become reality with the Hubble Space Telescope. The telescope's original October 1986 launch was scrapped after the loss of the space shuttle Challenger. When the telescope finally became operational in 1990, it began to return unprecedented but flawed images. Its images were superior to those of Earth-bound instruments but slightly blurred due to an optical problem. In December 1993 astronauts from the space shuttle Endeavour performed five days of spacewalks to repair the telescope in orbit some 353 miles (569 kilometers) above the Earth. The repair worked, and Hubble began to deliver crystal-clear images. Vast Amounts of Data Hubble's images have helped to pin down the age of the universe, which the expansion rate of pulsating stars suggests is some 13 billion to 14 billion years. Hubble has also captured images of many ancient galaxies, in all stages of evolution, and so lets scientists see back into the past days of a young and developing universe. The telescope was also instrumental in the discovery of dark energy, a little-known but ubiquitous force that works against gravity and contributes to the ongoing expansion of the universe. Hubble also measures the atmospheres of planets outside our own solar system, exploring their compositions and building data that could someday aid the search for extraterrestrial life. Despite its many achievements, Hubble is likely nearing the end of its life. The telescope is due for its last periodic servicing in May 2009. Its successor, the James Webb Space Telescope, is scheduled for launch in 2013. The new instrument will orbit much farther from Earth (940,000 miles/1.5 million kilometers)—the better to peer farther through the dust of space into the earliest formations of stars, solar systems, and galaxies. Other Observatories The Hubble is just one of NASA's orbiting "great observatories." The group also includes the Spitzer Space Telescope and the Chandra X-ray Observatory. Spitzer is an infrared orbiting telescope that can detect distant or faint sources of radiation that would otherwise be distorted by Earth's atmosphere. Spitzer scientists often describe their mission as a search for "the old" (the universe's earliest stars and galaxies), "the cold" (brown dwarfs, possibly stars that failed to ignite, and circumstellar discs, broad rings of material orbiting a star) and "the dirty" (dust-obscured processes such as star and planet formation). Chandra captures the rays that emit from the universe's most violent events, such as supernovae. This radiation sheds light on the life cycles of stars, the formation of black holes, and the nature of quasars.

Origins of the Universe, Big Bang Theory Information, Big Bang Facts, News, Photos -- National Geographic

Origins of the Universe, Big Bang Theory Information, Big Bang Facts, News, Photos -- National Geographic

The beginning

The most popular theory of our universe's origin centers on a cosmic cataclysm unmatched in all of history—the big bang. This theory was born of the observation that other galaxies are moving away from our own at great speed, in all directions, as if they had all been propelled by an ancient explosive force.
Before the big bang, scientists believe, the entire vastness of the observable universe, including all of its matter and radiation, was compressed into a hot, dense mass just a few millimeters across. This nearly incomprehensible state is theorized to have existed for just a fraction of the first second of time.
Big bang proponents suggest that some 10 billion to 20 billion years ago, a massive blast allowed all the universe's known matter and energy—even space and time themselves—to spring from some ancient and unknown type of energy.
The theory maintains that, in the instant—a trillion-trillionth of a second—after the big bang, the universe expanded with incomprehensible speed from its pebble-size origin to astronomical scope. Expansion has apparently continued, but much more slowly, over the ensuing billions of years.
Scientists can't be sure exactly how the universe evolved after the big bang. Many believe that as time passed and matter cooled, more diverse kinds of atoms began to form, and they eventually condensed into the stars and galaxies of our present universe.
Origins of the Theory
A Belgian priest named Georges Lemaître first suggested the big bang theory in the 1920s when he theorized that the universe began from a single primordial atom. The idea subsequently received major boosts by Edwin Hubble's observations that galaxies are speeding away from us in all directions, and from the discovery of cosmic microwave radiation by Arno Penzias and Robert Wilson.
The glow of cosmic microwave background radiation, which is found throughout the universe, is thought to be a tangible remnant of leftover light from the big bang. The radiation is akin to that used to transmit TV signals via antennas. But it is the oldest radiation known and may hold many secrets about the universe's earliest moments.
The big bang theory leaves several major questions unanswered. One is the original cause of the big bang itself. Several answers have been proposed to address this fundamental question, but none has been proven—and even adequately testing them has proven to be a formidable challenge.