What is Big Bang? When did it happen ? What is its Theory?
110345
the big bang is just another theory that scientists came up with. it's not proven, just like many other theories are not proven, but it is the most supported by scientists because it says that a molecule (atom) the size of alittle dot exploded 10-17 billion years ago, and kept expanding. this is mostly supported because today, we still see other objects in space red shifted on doppler system, which means that objects are moving away from us, and expanding the border of the universe.
206102
They believe that matter and energy were created during the Big Bang, however, that raises for a lot more questions, the most obvious one being:\n\nHow can matter and energy be created?
188399
About 15 billion years ago a tremendous explosion started the expansion of the universe. This explosion is known as the Big Bang. At the point of this event all of the matter and energy of space was contained at one point. What exisisted prior to this event is completely unknown and is a matter of pure speculation. This occurance was not a conventional explosion but rather an event filling all of space with all of the particles of the embryonic universe rushing away from each other. The Big Bang actually consisted of an explosion of space within itself unlike an explosion of a bomb were fragments are thrown outward. The galaxies were not all clumped together, but rather the Big Bang lay the foundations for the universe.
420014
the big bang happened 13.7 billion years ago.  also, i have something else for you to think about.  the universe is 13.7 billion years old, yet we can observe parts of the universe that are about 46 billion lightyears away.\n\nhttp://www.sciam.com/print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147
331026
The Big Bang theory itself, doesn't say anything about the *cause* of the explosion. It describes only how the Universe evolved after the explosion took place.\n\nThe reason is twofold.\nFirst of all, the models physicists use to describe the Universe, like General Relativity and Quantum Mechanics break down in the extreme conditions immediately after the initial explosion. However, they do a very good job in describing the existing data afterwards. And with the recent high precision measurements by satellite of the cosmic background that is very impressive.\n\nThe second reason is that GR and QM are only approximations of the correct theory. In fact they give different answers in the region were they overlap. Fortunately this happens only in extreme conditions, close to black holes for instance. And, you guessed it, in the microseconds after the Big Bang.\n\nConclusion: there is therefore a lot of room left to speculate. Not for the scientists though, because there are no data available for these initial moments of the Universe. No data means, nothing to test theories on.
356868
how else would the universe have come into creation?  Before time existed, there must have been nothing, and at the first possible moment of time, there must have been some minute form of matter.  Whether or not the universe was created in a big bang, I cannot know, since if the big bang theory is true (as well as the Big Crunch theory), then it is possible that the universe has already cycled many times.\n\nBeyond that though, the Big Bang theory does NOT say that the size of the initial chunk of matter was infinitessimally small, it just says that it was supercompact.  It was probably insanely large, but relatively small for all the matter it withheld.
188695
If I were you, I'd search it myself instead of asking people, but that's just me.\n\nThere are so many theories to how the universe started, in which the Big Bang theory is the most popular. In this theory, it all started with a single point with the same amount of matter in the universe and it was really really hot. Then it just explodes, continuing to expand at an alarming speed. It was so hot that not even the particles that made up atoms could not even form until the universe was expanded enough to cool down, and then the first atoms were made. Then it just continues to expand to where we are now.\n\nThat's one theory. I like the never-started theory. There was no beginning to our universe. The reason why the Big Bang theory is the most accepted theory is because we (us humans) like to think that there is a start to everything. It just makes sense that there is a beginning. And it's easier to build theories and ideas upon it.\n\nPS Penguins!!!
196438
In physical cosmology, the Big Bang is the scientific theory that the universe emerged from an enormously dense and hot state about 13.7 billion years ago. The Big Bang theory is based on the observed Hubble's law redshift of distant galaxies that when taken together with the cosmological principle indicate that space is expanding according to the Friedmann-Lemaître model of general relativity. Extrapolated into the past, these observations show that the universe has expanded from a state in which all the matter and energy in the universe was at an immense temperature and density. Physicists do not widely agree on what happened before this, although general relativity predicts a gravitational singularity (for reporting on some of the more notable speculation on this issue, see cosmogony).\n\nThe term Big Bang is used both in a narrow sense to refer to a point in time when the observed expansion of the universe (Hubble's law) began — calculated to be 13.7 billion (1.37 × 1010) years ago (±2%) — and in a more general sense to refer to the prevailing cosmological paradigm explaining the origin and expansion of the universe, as well as the composition of primordial matter through nucleosynthesis as predicted by the Alpher-Bethe-Gamow theory [1].\n\nOne consequence of the Big Bang is that the conditions of today's universe are different from the conditions in the past or in the future. From this model, George Gamow in 1948 was able to predict, at least qualitatively, the existence of cosmic microwave background radiation (CMB) [2]. The CMB was discovered in the 1960s and further validated the Big Bang theory over its chief rival, the steady state theory.\n\nThe Big Bang theory developed from observations and theoretical considerations. Observationally, it was determined that most spiral nebulae were receding from Earth, but those who made the observation weren't aware of the cosmological implications, nor that the supposed nebulae were actually galaxies outside our own Milky Way[3]. In 1927, the Belgian Catholic priest Georges Lemaître independently derived the Friedmann-Lemaître-Robertson-Walker equations from Albert Einstein's equations of general relativity and proposed, on the basis of the recession of spiral nebulae, that the universe began with the "explosion" of a "primeval atom"—what was later called the Big Bang[4].\n\nIn 1929, Edwin Hubble provided an observational basis for Lemaître's theory. He discovered that, relative to the Earth, the galaxies are receding in every direction at speeds directly proportional to their distance from the Earth. This fact is now known as Hubble's law [5]. Given the cosmological principle whereby the universe, when viewed on sufficiently large distance scales, has no preferred directions or preferred places, Hubble's law suggested that the universe was expanding contradicting the infinite and unchanging static universe scenario developed by Einstein.\n\nThis idea allowed for two opposing possibilities. One was Lemaître's Big Bang theory, advocated and developed by George Gamow. The other possibility was Fred Hoyle's steady state model in which new matter would be created as the galaxies moved away from each other. In this model, the universe is roughly the same at any point in time[6]. It was actually Hoyle who coined the name of Lemaître's theory, referring to it sarcastically as "this big bang idea" during a program broadcast on March 28, 1949 by the BBC Third Programme. Hoyle repeated the term in further broadcasts in early 1950, as part of a series of five lectures entitled The Nature of Things. The text of each lecture was published in The Listener a week after the broadcast, the first time that the term "big bang" appeared in print. [7]
1162299
The scientific theory is that the Universe started as a fluctuation of the vacuum. Such vacuum fluctuations make appear a small amount of energy, for a small time. \n\nNot so the Big Bang. That was a HUGE fluctuation. So big that a lot of energy came to appearance in the form of mass, elementary particles. These particles started expanding, before the vacuum could reclaim the energy.\n\nAnd it is still expanding today. 14 billion years later.\n\nNow for some speculation. Is our Universe the only one? Maybe not. The Big Bang was one big fluctuation, maybe other smaller or bigger, take place all the time.\nBut most of these fluctuations will produce Universes in which conditions are just not suitable for life.\nThe Universe we observe is by necessity one in which the conditions are just right for us to have evolved into Homo Sapiens capable of asking questions.
51258
The Universe was created by an event known as the "BIG BANG" and has been increasing ever since.  There are many theories about what the universe will do in the future Ex. ever increasing, saddle shape, or will is contract and implode creating a massive black hole.\n\nVery cool and interesting stuff.\n\nCheck this site for more on the "BIG BANG"
725562
The essence of the Big Bang theory is pretty simple:  sometime billions of years ago the universe began;  everything now in the universe was created from energy/matter that was compacted into a really, really small volume/space, and indeed that really, really small volume/space was all there was to the universe at that moment; and since the universe began, it's been expanding.  These are the essential points of the theory.  Over time, we've added new details, such as pinning down the age of the universe to within a few hundred million years (last I heard, we thought it was 13.7 +/- 0.2 billion years old).  And a lot of theoretical and observational work have gone into investigating and refining the theory.\n\nAs to why we think that there was a Big Bang instead of, say, a universe which had always existed or a universe which came into being pretty much fully formed, the main reason and the reason we started thinking there was a Big Bang in the first place is because of very peculiar observations that we can make of distant galaxies.  This observation is that, except for a bunch galaxies which are both nearby and gravitationally bound to our own galaxy, all the galaxies we can see are moving away from both our galaxy and all other galaxies.  Also, the speed with which a galaxy is moving away from us depends directly on how far away from us it is (e.g. galaxies farther away from us are moving away from us faster than galaxies which are closer).  And the reason we first infered a Big Bang from this is that if you imagine running this movement backwards, doing a cosmic rewind if you will, then all the galaxies will be moving back towards each other, and eventually will all find themselves in the same place.\n\nSeveral years after this observation, a key predicition of the Big Bang theory was verified.  When the universe was young, it was also really hot and so for a time would have given off light all its own (I'm simplifying things a bit, but these are the essential facts as we know them).  It was predicted that some of this light should still be around.  And, lo and behold, at the very same time that people were making this prediction and beginning to think of looking for it, practically right down the road some experimentalists stumbled upon it accidentally.\n\nSo, in short and hopefully simple words, that's what the Big Bang is and why we think it happened.
126342
There is hard, physical evidence that the Big Bang happened. There is NO hard, physical evidence that the god of the Bible existed, exists, or will ever exist.\n\nBUT..! Belief in a supreme being of some kind is a logical belief that can exist right along with the Big Bang. Most physicists and cosmologists agree that there are no physical (as in physics)constraints that can disallow a Big Bang. Something from nothing happens constantly in the vacuum of space!!!!! At sizes smaller than a proton, so-called virtual particles pop into existence all the time. Quantum physics has shown that at these infinitesimal sizes immense amounts of energy exist which can easily "produce" new matter from nothing. The bottom line is that these physical laws exist, and the next question any reasonable person would ask is who or what made these laws, the same physical rules that make a Big Bang possible?
395881
I hope that most of the previous answerers were joking. The Big-Bang theory is the best theory of the origin of the Universe that we have so far. It was formulated based on the expansion of the Universe, that we know because everywhere we look on the sky, on average, the galaxies are getting away from us, not because the "red radiation" but because of redshift, the light emitted by the galaxies is redshifted, which means that they are getting away form us (check at the Dopler effect to understand this), and the farther away the faster they are getting away, check: Hubble law. This means that the expansion is accelerated, then is natural to thing that going to the past the galaxies were closer together and there was a moment when they actually were in a single point of infinite density and energy, a singularity. The big bang states then that something caused this singularity to explode producing the accelerated Universe we see today with all the things inside. Now, Science can tell more or less how the Universe has evolved since a brief moment (less than one second) after big-bang until know, but it can not tell what happened at the "zero time" because general relativity breaks down in the singularity. Nobody know what triggered this big explosion.
732289
the complete concept of big bang is explained here... beginning to the end.\n\nWhat happened before the big bang, evidence of the big bang theory, what caused the big bang, big bang theory of evolution are some of the questions asked on the Internet today.\n\nWhat do we mean when we talk of big bang theory? It is in the last 30 years or so that scientists across the world accepted and confirmed the existence of the big bang theory. It has more or less been proved that the evolution of the Cosmos occurred with a big bang. There is no further denial on this fact of big bang theory.\n\nThis evidence put forward by the scientific community is further corroborated firmly by spirituality. How?\n\n\nLet us travel to the beginning of time when the Cosmos is in the process of complete dissolution. What happens after the complete dissolution of the Cosmos? In the field of the spirituality... everything contained in the Cosmos is but an illusion... an act of Maya (Veil of ignorance). There is nothing in the Cosmos which is solid in nature.\n\nBroken down to the basic building block of the universe... everything in the whole of Cosmos is a cluster of atoms and molecules. Then what constitutes the Cosmos itself? Spirituality spells out the truth... everything contained in the whole of Cosmos is but souls atmans and ether, the inert matter.\n\nEther is that dark black substance which fills up the void existing all over the Cosmos. Apart from ether spirituality defines the Cosmos consisting of souls atmans and nothing more. Whatever is visible to the physical senses of a human being nay every living being is limited to the use of the physical senses. Beyond the senses.... nothing exists in the whole of Cosmos except the world of souls atmans and ether.\n\n\nThe dissolution of the Cosmos is best defined in Bhagavad Gita, the sacred doctrine put forward by Lord Krishna in the battlefield of Kurushetra. As per Bhagavad Gita Almighty God is defined as, "the sum total of all the purified souls atmans in the Cosmos at a given point of time"! At the time of the dissolution of the Cosmos all the souls atmans in the Cosmos having purified themselves collect together to form what we know as God Almighty.\n\nThis collective power of all the souls atmans in the Cosmos... the size of half a thumb as detailed in Bhagavad Gita and unable to contain itself for long explodes with a big bang. And this big bang leads to formation of a new Cosmos... a new series of universes, galaxies, cluster of stars and solar systems.\n\nEvery new Cosmos can begin only after a big bang. No Cosmos can form without the big bang having occurred! The occurrence of the big bang announces the formation of a new Cosmos. It is the big bang theory which paves way for all the souls atmans in the Cosmos to start their cosmic travel of 8.4 million manifestations.\n\n\nThe big bang having occurred... it takes millions and billions of years before the system becoming conducive for life to germinate. As the conditions became conducive for life to germinate on Mother Earth... the souls atmans (within the gravitational pull of the solar system) settled on Mother Earth. This gave birth to life on Mother Earth.\n\nStarting the journey as an amoeba and finally culminating into the form of a human being... it is only as a human being that one reaches the end of life... gains enlightenment and finally salvation!\n\nThe big bang theory announces the start of a new Cosmos... the beginning of life for every soul atman on its cosmic journey!\n\n\nSpirituality or otherwise... the start of the Cosmos could not have occurred without a big bang. It is only the big bang theory which governs the start of cosmic system. There is no other means which could have led to start of a new Cosmos without a big bang.\n\nThe big bang is that phenomenon in the life of a Cosmos without which the existence of God Almighty himself would get negated. God Almighty being the sum total of all purified souls atmans
326376
The Big Bang Model is a broadly accepted theory for the origin and evolution of our universe. It postulates that 12 to 14 billion years ago, the portion of the universe we can see today was only a few millimeters across. It has since expanded from this hot dense state into the vast and much cooler cosmos we currently inhabit. We can see remnants of this hot dense matter as the now very cold cosmic microwave background radiation which still pervades the universe and is visible to microwave detectors as a uniform glow across the entire sky.\n\nFurther readings:\n    * Peebles, P.J.E., Schramm, D.N., Turner, E.L. & R.G. Kron 1991, "The Case for the Relativistic Hot Big Bang Cosmology", Nature, 352, 769 - 776.\n    * Peebles, P.J.E., Schramm, D.N., Turner, E.L. & R.G. Kron 1994, "The Evolution of the Universe'', Scientific American, 271, 29 - 33.\n    * Will, Clifford, "Was Einstein Right?"
564094
georges lemaître derived equations from general relativity and proposed that the universe began with an explosion of an extremely dense particle of matter.  the theory was later developed by george gamow, alan guth, and others. the big bang theory is no longer like georges lemaître's original hypothesis.  fred hoyle inadvertently gave the theory its name in a dismissive remark.\n\nread these pages:\nhttp://en.wikipedia.org/wiki/Big_Bang\nhttp://en.wikipedia.org/wiki/Cosmic_infulation\nhttp://en.wikipedia.org/wiki/Georges_Lema%C3%AEtre\nhttp://en.wikipedia.org/wiki/George_Gamow\nhttp://en.wikipedia.org/wiki/Alan_Guth\n\nalso read this page:\nhttp://www.sciam.com/print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147
71447
big bang. and its a big universe, we cant be all alone