How the universe was made from the Big Bang to the human body. Big Bang Theory, currently accepted explanation of the beginning of the universe. The big bang theory proposes that the universe was once extremely compact, dense, and hot. Some original event, a cosmic explosion called the big bang, occurred about 13.7 billion years ago, and the universe has since been expanding and cooling. The theory is based on the mathematical equations, known as the field equations, of the general theory of relativity set forth in 1915 by Albert Einstein. In 1922 Russian physicist Alexander Friedmann provided a set of solutions to the field equations. These solutions have served as the framework for much of the current theoretical work on the big bang theory. American astronomer Edwin Hubble provided some of the greatest supporting evidence for the theory with his 1929 discovery that the light of distant galaxies was universally shifted toward the red end of the spectrum (see Redshift). Once tired light theories that light slowly loses energy naturally, becoming more red over time were dismissed, this shift proved that the galaxies were moving away from each other. Hubble found that galaxies farther away were moving away proportionally faster, showing that the universe is expanding uniformly. However, the universes initial state was still unknown.

The Universe is a dangerous place. This programme investigates our survival in space.Although you can't see asteroids with the naked eye, a good pair of binoculars or a small telescope will help you to spot them. Most asteroids are in stable solar orbits. However, Jupiter's gravitational field can sometimes pull bodies out of orbit, and send them off at random paths through the Solar System. Could one of these bodies strike the Earth one day? We`re all licky to be alive - because the universe keeps trying to wipe us out. Life of Earth has been nearly eradicated on twenty occassions. Sam Neil voyages out into space of the cosmic killers which may one threaten our very existence -comes and asteroids. The world-line of a typical oxygen atom in the universe is a complex one, particularly when one takes into account not just supernovae, stars and planets but also the Cambrian revolution, the Permian extinction, the dinosaurs and Homo neanderthalensis. In fact, it is almost a miracle that the Homo sapiens of today - in the form of Lawrence Krauss - can track down the odyssey of an individual oxygen atom, which requires a great deal of knowledge in the physical sciences, chemistry and biology

Black holes are the Universe's ultimate monsters, sucking everything into their super-dense centres. Black holes were once thought to be the monsters of the Universe, devouring everything around them in a frenzied cosmic feast. But now astronomers think that rather than being a space menace, black holes may be fundamental to the creation of galaxies. Black holes are regions of space where gravity is so strong that not even light can escape, making them impossible to see. But we can see the stuff that is being sucked in to these massive cosmic vacuum cleaners. Anything that approaches a black hole is first torn apart by its immense gravitational force and then forms a flat rotating disc that spirals into the hole. Black Hole, an extremely dense celestial body that has been theorized to exist in the universe. The gravitational field of a black hole is so strong that, if the body is large enough, nothing, including electromagnetic radiation, can escape from its vicinity. The body is surrounded by a spherical boundary, called a horizon, through which light can enter but not escape; it therefore appears totally black.

There are over four hundred thousand million stars in our Galaxy alone. Where do we start looking for life? With hundreds of telescopes now involved in the SETI programme, there is lots of data to look through. Spotting strong signals is easy, but finding a weak signal takes lots of computer time. When you look at it mathematically and statistically the chances of complex life developing is extremely low. "We have good reason to believe that Earth is not a typical planet. "The sun's output has increased so much over time that we might expect life to have died out. "But the Earth has adapted by altering the atmosphere around it. "When you look at it mathematically and statistically the chances of complex life developing is extremely low. "We have good reason to believe that Earth is not a typical planet. "The sun's output has increased so much over time that we might expect life to have died out. "But the Earth has adapted by altering the atmosphere around it. "I think we can conclude from this that we are probably effectively alone in the universe." He said complex organisms took a long time to develop on Earth, not appearing until a good fraction "through the likely lifespan of the planet". "This is consistent with the notion that structurally complex life, particularly sentient beings, are very rare - and most planets never reach that stage of evolution," said Professor Watson. "On the rare occasions when sentient life does arise, it will almost always find itself awakening towards the end of the life of the biosphere in which it has arisen."

How could humans migrate from planet Earth? Before you leave Mars is closer in temperature to Earth than any of the other planet in the Solar System. But don't let this catch you off your guard. Mars' weather is even more unpredictable than our own. We recommend a summer visit, when the temperature can reach a pleasant 27C. But keep an eye on the weather forecast! Storms can sweep across the whole planet. Within days, the temperature can plummet by 20 degrees. Travellers in the winter months should note that Mars can reach a bitter -133C. One final word of warning - make sure you are prepared for dust storms. Tornadoes as large as eight kilometers high have been seen causing havoc across the Martian landscape. The Hubble Space Telescope may have discovered as many as 100 new planets orbiting stars in our galaxy. Hubble's harvest comes from a sweep of thousands of stars in the dome-like bulge of the Milky Way. If confirmed it would almost double the number of planets known to be circling other stars to about 230. The discovery will lend support to the idea that almost every sunlike star in our galaxy, and probably the Universe, is accompanied by planets.

If humans are ever to reach deep space, there will need to be some revolutionary changes in transport. Dreamt up at the beginning of last century, solar sails are now moving a step closer to reality, as one of the most feasible ways of travelling into deep space. They are lightweight panels made from reflective material that act like the sails of a boat. Rather than using wind, the sails are actually propelled by light. Unbelievable as it may seem, the stream of light particles (called photons) emitted from the Sun are strong enough to push a mini-spacecraft right out of the Solar System and beyond into interstellar space. Towards the end of the nineteenth century, a number of phenomena involving light were observed which could not be properly explained by the wave model. One such phenomenon was the photoelectric effect observed in 1887 by Hertz and further in 1888 by Hallwachs, who showed that a negatively charged zinc plate loses its charge when it is exposed to ultraviolet light, but not if exposed to white light. The experiments below demonstrate the photoelectric effect:

In strictly physical terms, the total universe is the sum of all matter that exists and the space in which all events occur or could occur. The part of the universe that can be seen or otherwise observed to have occurred is called the known universe, observable universe, or visible universe. Because cosmic inflation removes vast parts of the total universe from our observable horizon, most cosmologists accept that it is impossible to observe the whole continuum and may use the expression our universe, referring to only that which is knowable by human beings in particular. In cosmological terms, the universe is thought to be a finite or infinite space-time continuum in which all matter and energy exist. Some scientists hypothesize that the universe may be part of a system of many other universes, known as the multiverse.

The most important result of physical cosmology, the understanding that the universe is expanding, is derived from redshift observations and quantified by Hubble's Law. Extrapolating this expansion back in time, one approaches a gravitational singularity, an abstract mathematical concept, which may or may not correspond to reality. This gives rise to the Big Bang theory, the dominant model in cosmology today. The age of the universe from the time of the Big Bang, according to current information provided by NASA's WMAP (Wilkinson Microwave Anisotropy Probe), is estimated to be about 13.7 billion (1.37 × 1010) years, with a margin of error of about 1 % (± 200 million years). Other methods of estimating the age of the universe give different ages with a range from 11 billion to 20 billion. Most of the estimates cluster in the 13-15 billion year range. A fundamental aspect of the Big Bang can be seen today in the observation that the farther away galaxies are from us, the faster they move away from us. It can also be seen in the cosmic microwave background radiation, which is the much-attenuated radiation that originated soon after the Big Bang. This background radiation is remarkably uniform in all directions, which cosmologists have attempted to explain by an early period of inflationary expansion following the Big Bang. In the 1977 book The First Three Minutes, Nobel Prize-winner Steven Weinberg laid out the physics of what happened just moments after the Big Bang. As with most things in physics, that certainly wasn't the end of the story, as attested by the update and reissue of The First Three Minutes in 1993.

Until recently, the first hundredth of a second was a bit of a mystery, leaving Weinberg and others unable to describe exactly what the universe would have been like. New experiments at the Relativistic Heavy Ion Collider in Brookhaven National Laboratory have provided physicists with a glimpse through this curtain of high energy, so they can directly observe the sorts of behavior that might have been taking place in this time frame. At these energies, the quarks that comprise protons and neutrons were not yet joined together, and a dense, superhot mix of quarks and gluons, with some electrons thrown in, was all that could exist in the microseconds before it cooled enough to form into the sort of matter particles we observe today.

Fast forwarding to after the existence of matter, more information is coming in on the formation of galaxies. It is believed that the earliest galaxies were tiny "dwarf galaxies" that released so much radiation they stripped gas atoms of their electrons. This gas, in turn, heated up and expanded, and thus was able to obtain the mass needed to form the larger galaxies that we know today. Current telescopes are just now beginning to have the capacity to observe the galaxies from this distant time. Studying the light from quasars, they observe how it passes through the intervening gas clouds. The ionization of these gas clouds is determined by the number of nearby bright galaxies, and if such galaxies are spread around, the ionization level should be constant. It turns out that in galaxies from the period after cosmic reionization there are large fluctuations in this ionization level. The evidence seems to confirm the pre-ionization galaxies were less common and that the post-ionization galaxies have 100 times the mass of the dwarf galaxies. The next generation of telescopes should be able to see the dwarf galaxies directly, which will help resolve the problem that many astronomical predictions in galaxy formation theory predict more nearby small galaxies.

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