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The Big Bang Theory explains how the universe began with an infinitely hot and dense single point that inflated to form the ever-expanding cosmos we see today.

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The Big Bang is science's best explanation for how the universe began. According to the theory, the universe started out much hotter and much denser than it is today, and expanded and cooled over time.

Though the term may sound like the universe began with a giant explosion, many scientists say that's not part of the theory. An explosion implies that something exploded, or expanded, from one center point outward into space. In fact, the Big Bang theory suggests that space itself expanded.

"If it were an explosion it would have a center," said physicist Paul Steinhardt, director of the Princeton Center for Theoretical Science at Princeton University in Princeton, N.J. "We actually observe that everything is moving away from everything else. It's really about an expansion of the universe ."

Instead of a center from which everything expanded, scientists think space is expanding everywhere, in all directions, equally.

"Space isn't just something that sits there and things happen in it - space is a dynamical thing," said Andreas Albrecht, a theoretical physicist at the University of California, Davis.

Though to some, the question of whether there was an explosion is just semantics.

"I think anything that starts out at 10 to the 40th degrees, and is doubling in size every tiny, tiny fraction of a second - I think you'd want to call that an explosion," Albrecht said. "But it has different features than someone setting off a bomb in the desert."

Another confusing aspect of the theory is the idea that at the very moment of the Big Bang, the universe existed in a single point, a singularity of infinite temperature and density. Although this is what the theory says, scientists think that's where the Big Bang theory becomes inadequate. Those infinities are signs that the mathematics have broken down and fail to truly describe the universe.

In order to fully understand what happened then, scientists think we need a better fundamental theory of physics that can incorporate our current description of the very small ( general relativity ). As of now, those two theories are irreconcilable, and they collide at the moment of the Big Bang.

Caption: The above photo is not of the Big Bang (there are no photos of it). The Hubble Space Telescope image is of the Crab Nebula. Credit: NASA/ESA and Jeff Hester (Arizona State University)

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The Big Bang is science's best explanation for how the universe began. According to the theory, the universe started out much hotter and much denser than it is today, and expanded and cooled over time. Though the term may sound like the universe began with a giant explosion, many scientists say that's not part of the theory.

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Credit: SRON

The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10⁻³⁴ of a second or so old - that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age - it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light. During this period, the universe doubled in size at least 90 times, going from subatomic-sized to golf-ball-sized almost instantaneously.

The work that goes into understanding the expanding universe comes from a combination of theoretical physics and direct observations by astronomers. However, in some cases astronomers have not been able to see direct evidence - such as the case of gravitational waves associated with the cosmic microwave background, the leftover radiation from the Big Bang. A preliminary announcement about finding these waves in 2014 was quickly retracted, after astronomers found the signal detected could be explained by dust in the Milky Way.

According to NASA, after inflation the growth of the universe continued, but at a slower rate. As space expanded, the universe cooled and matter formed. One second after the Big Bang, the universe was filled with neutrons, protons, electrons, anti-electrons, photons and neutrinos.

During the first three minutes of the universe, the light elements were born during a process known as Big Bang nucleosynthesis. Temperatures cooled from 100 nonillion (10 ³²) Kelvin to 1 billion (10 ⁹) Kelvin, and protons and neutrons collided to make deuterium, an isotope of hydrogen. Most of the deuterium combined to make helium, and trace amounts of lithium were also generated.

For the first 380,000 years or so, the universe was essentially too hot for light to shine, according to France's National Center of Space Research (Centre National d'Etudes Spatiales, or CNES). The heat of creation smashed atoms together with enough force to break them up into a dense plasma, an opaque soup of protons, neutrons and electrons that scattered light like fog.

Roughly 380,000 years after the Big Bang, matter cooled enough for atoms to form during the era of recombination, resulting in a transparent, electrically neutral gas, according to NASA. This set loose the initial flash of light created during the Big Bang, which is detectable today as cosmic microwave background radiation. However, after this point, the universe was plunged into darkness, since no stars or any other bright objects had formed yet.

About 400 million years after the Big Bang, the universe began to emerge from the cosmic dark ages during the epoch of reionization. During this time, which lasted more than a half-billion years, clumps of gas collapsed enough to form the first stars and galaxies, whose energetic ultraviolet light ionized and destroyed most of the neutral hydrogen.

Although the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity, about 5 or 6 billion years after the Big Bang, according to NASA, a mysterious force now called dark energy began speeding up the expansion of the universe again, a phenomenon that continues today.

A little after 9 billion years after the Big Bang, our solar system was born.

The Big Bang

The Big Bang did not occur as an explosion in the usual way one think about such things, despite one might gather from its name. The universe did not expand into space, as space did not exist before the universe, according to NASA Instead, it is better to think of the Big Bang as the simultaneous appearance of space everywhere in the universe. The universe has not expanded from any one spot since the Big Bang - rather, space itself has been stretching, and carrying matter with it.

Since the universe by its definition encompasses all of space and time as we know it, NASA says it is beyond the model of the Big Bang to say what the universe is expanding into or what gave rise to the Big Bang. Although there are models that speculate about these questions, none of them have made realistically testable predictions as of yet.

In 2014, scientists from the Harvard-Smithsonian Center for Astrophysics announced that they had found a faint signal in the cosmic microwave background that could be the first direct evidence of gravitational waves, themselves considered a " smoking gun" for the Big Bang. The findings were hotly debated, and astronomers soon retracted their results when they realized dust in the Milky Way could explain their findings. mysterious ripples

The globular cluster NGC 6397 contains around 400,000 stars and is located about 7,200 light years away in the southern constellation Ara. With an estimated age of 13.5 billion years, it is likely among the first objects of the Galaxy to form after the Big Bang.

Credit: European Southern Observatory

The universe is currently estimated at roughly 13.8 billion years old, give or take 130 million years. In comparison, the solar system is only about 4.6 billion years old.

This estimate came from measuring the composition of matter and energy density in the universe. This allowed researchers to compute how fast the universe expanded in the past. With that knowledge, they could turn the clock back and extrapolate when the Big Bang happened. The time between then and now is the age of the universe.

Scientists think that in the earliest moments of the universe, there was no structure to it to speak of, with matter and energy distributed nearly uniformly throughout. According to NASA, the gravitational pull of small fluctuations in the density of matter back then gave rise to the vast web-like structure of stars and emptiness seen today. Dense regions pulled in more and more matter through gravity, and the more massive they became, the more matter they could pull in through gravity, forming stars, galaxies and larger structures known as clusters, superclusters, filaments and walls, with "great walls" of thousands of galaxies reaching more than a billion light years in length. Less dense regions did not grow, evolving into area of seemingly empty space called voids.

Until about 30 years ago, astronomers thought that the universe was composed almost entirely of ordinary atoms, or "baryonic matter," According to NASA. However, recently there has been ever more evidence that suggests most of the ingredients making up the universe come in forms that we cannot see.

It turns out that atoms only make up 4.6 percent of the universe. Of the remainder, 23 percent is made up of dark matter, which is likely composed of one or more species of subatomic particles that interact very weakly with ordinary matter, and 72 percent is made of dark energy, which apparently is driving the accelerating expansion of the universe.

When it comes to the atoms we are familiar with, hydrogen makes up about 75 percent, while helium makes up about 25 percent, with heavier elements making up only a tiny fraction of the universe's atoms, according to NASA.

The shape of the universe and whether or not it is finite or infinite in extent depends on the struggle between the rate of its expansion and the pull of gravity. The strength of the pull in question depends in part on the density of the matter in the universe.

If the density of the universe exceeds a specific critical value, then the universe is " closed" and "positive curved" like the surface of a sphere. This means light beams that are initially parallel will converge slowly, eventually cross and return back to their starting point, if the universe lasts long enough. If so, according to NASA, the universe is not infinite but has no end, just as the area on the surface of a sphere is not infinite but has no beginning or end to speak of. The universe will eventually stop expanding and start collapsing in on itself, the so-called "Big Crunch."

If the density of the universe is less than this critical density, then the geometry of space is " open" and "negatively curved" like the surface of a saddle. If so, the universe has no bounds, and will expand forever.

If the density of the universe exactly equals the critical density, then the geometry of the universe is " flat" with zero curvature like a sheet of paper, according to NASA. If so, the universe has no bounds and will expand forever, but the rate of expansion will gradually approach zero after an infinite amount of time. Recent measurements suggest that the universe is flat with only a 2 percent margin of error.

It is possible that the universe has a more complicated shape overall while seeming to possess a different curvature. For instance, the universe could have the shape of a torus, or doughnut.

In the 1920s, astronomer Edwin Hubble discovered the universe was not static. Rather, it was expanding; a find that revealed the universe was apparently born in a Big Bang.

After that, it was long thought the gravity of matter in the universe was certain to slow the expansion of the universe. Then, in 1998, the Hubble Space Telescope's observations of very distant supernovae revealed that a long time ago, the universe was expanding more slowly than it is today. In other words, the expansion of the universe was not slowing due to gravity, but instead inexplicably was accelerating. The name for the unknown force driving this accelerating expansion is dark energy, and it remains one of the greatest mysteries in science.

Additional reporting by Nola Taylor Redd and Elizabeth Howell, Space.com contributors.

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Our Expanding Universe: Age, History & Other Facts

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The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10-34 of a second or so old - that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age - it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light.

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http://www.skyandtelescope.com/astronomy-resources/how-did-the-universe-begin-happened-big-bang/

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Evidence for the Big Bang | National Schools' Observatory

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You cannot look in new stars, like the Sun, for this evidence, because they contain elements that were created in previous generations of stars. As such, the composition of new stars will be very different from the composition of stars that existed 7 billion years ago, shortly after the Big Bang.

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http://www.universetoday.com/54756/what-is-the-big-bang-theory/

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Extra information and question 3
http://curious.astro.cornell.edu/about-us/102-the-universe/cosmology-and-the-big-bang/the-big-bang/592-can-we-find-the-place-where-the-big-bang-happened-intermediate

Video for Question 4
http://ca.pbslearningmedia.org/resource/ess05.sci.ess.eiu.microwave/evidence-for-the-big-bang-theory/

Big Bang Theory
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

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The theory that says the universe was created when a nebula started spinning. It slowly span faster, creating the universe somehow.
The Big Bang Theory is the leading explanation about how the universe began. At its simplest, it talks about the universe as we know it starting with a small singularity, then inflating over the next 13.8 billion years to the cosmos that we know today. Because current instruments don't allow astronomers to peer back at the universe's birth, much of what we understand about the Big Bang Theory comes from mathematical theory and models. Astronomers can, however, see the "echo" of the expansion through a phenomenon known as the cosmicmicrowave background. The phrase "Big Bang Theory" has been popular among astrophysicists for decades, but it hit the mainstream in 2007 when a comedy show with the same name premiered on CBS. The show follows the home and academic life of several researchers (including an astrophysicist).

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http://www.dummies.com/education/science/physics/string-theorys-notions-of-the-big-bang-theory/

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http://www.dummies.com/education/science/physics/string-theorys-notions-of-the-big-bang-theory/

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https://www.youtube.com/watch?v=DmUiCweDic4

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#3 Website

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How was our Universe created? How did it come to be the seemingly infinite place we know of today? And what will become of it, ages from now? These are the questions that have been puzzling philosophers and scholars since the beginning the time, and led to some pretty wild and interesting theories. Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding cosmos. This is known as The Big Bang Theory.

For almost a century, the term has been bandied about by scholars and non-scholars alike. This should come as no surprise, seeing as how it is the most accepted theory of our origins. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there of this, and what does the theory say about the long-term projections for our Universe?

The basics of the Big Bang theory are fairly simple. In short, the Big Bang hypothesis states that all of the current and past matter in the Universe came into existence at the same time, roughly 13.8 billion years ago. At this time, all matter was compacted into a very small ball with infinite density and intense heat called a Singularity. Suddenly, the Singularity began expanding, and the universe as we know it began.

While this is not the only modern theory of how the Universe came into being - for example, there is the Steady State Theory or the Oscillating Universe Theory - it is the most widely accepted and popular. Not only does the model explain the origin of all known matter, the laws of physics, and the large scale structure of the Universe, it also accounts for the expansion of the Universe and a broad range of other phenomena.

Timeline of the Big Bang Theory

Working backwards from the current state of the Universe, scientists have theorized that it must have originated at a single point of infinite density and finite time that began to expand. After the initial expansion, the theory maintains that Universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements later coalesced through gravity to form stars and galaxies.

This all began roughly 13.8 billion years ago, and is thus considered to be the age of the universe. Through the testing of theoretical principles, experiments involving particle accelerators and high-energy states, and astronomical studies that have observed the deep universe, scientists have constructed a timeline of events that began with the Big Bang and has led to the current state of cosmic evolution.

However, the earliest times of the Universe - lasting from approximately 10⁻⁴³ to 10⁻¹¹ seconds after the Big Bang - are the subject of extensive speculation. Given that the laws of physics as we know them could not have existed at this time, it is difficult to fathom how the Universe could have been governed. What's more, experiments that can create the kinds of energies involved have not yet been conducted. Still, many theories prevail as to what took place in this initial instant in time, many of which are compatible.

Singularity Epoch

Also known as the Planck Epoch (or Planck Era), this was the earliest known period of the Universe. At this time, all matter was condensed on a single point of infinite density and extreme heat. During this period, it is believed that the quantum effects of gravity dominated physical interactions and that no other physical forces were of equal strength to gravitation.

This Planck period of time extends from point 0 to approximately 10-43 seconds, and is so named because it can only be measured in Planck time. Due to the extreme heat and density of matter, the state of the universe was highly unstable. It thus began to expand and cool, leading to the manifestation of the fundamental forces of physics.

From approximately 10separating from gauge forces, which account for strong and weak nuclear forces and electromagnetism.⁻⁴³ second and 10⁻³⁶, the universe began to cross transition temperatures. It is here that the fundamental forces that govern the Universe are believed to have began separating from each other. The first step in this was the force of gravitation

Then, from 10-36 to 10-32 seconds after the Big Bang, the temperature of the universe was low enough (10 ²⁸ K) that the forces of electromagnetism (strong force) and weak nuclear forces (weak interaction) were able to separate as well, forming two distinct forces.

Inflation Epoch

With the creation of the first fundamental forces of the universe, the Inflation Epoch began, lasting from 10-32 seconds in Planck time to an unknown point. Most cosmological models suggest that the Universe at this point was filled homogeneously with a high-energy density, and that the incredibly high temperatures and pressure gave rise to rapid expansion and cooling.

This began at 10⁻³⁷ seconds, where the phase transition that caused for the separation of forces also led to a period where the universe grew exponentially. It was also at this point in time that baryogenesis occurred, which refers to a hypothetical event where temperatures were so high that the random motions of particles occurred at relativistic speeds.

As a result of this, particle-antiparticle pairs of all kinds were being continuously created and destroyed in collisions, which is believed to have led to the predominance of matter over antimatter in the present universe. After inflation stopped, the universe consisted of a quark-gluon plasma, as well as all other elementary particles. From this point onward, the Universe began to cool and matter coalesced and formed.

Cooling Epoch

As the universe continued to decrease in density and temperature, the energy of each particle began to decrease and phase transitions continued until the fundamental forces of physics and elementary particles changed into their present form. Since particle energies would have dropped to values that can be obtained by particle physics experiments, this period onward is subject to less speculation.

For example, scientists believe that about 10⁻¹¹ seconds after the Big Bang, particle energies dropped considerably. At about 10⁻⁶ seconds, quarks and gluons combined to form baryons such as protons and neutrons, and a small excess of quarks over antiquarks led to a small excess of baryons over antibaryons.

Since temperatures were not high enough to create new proton-antiproton pairs (or neutron-anitneutron pairs), mass annihilation immediately followed, leaving just one in 10 ¹⁰ of the original protons and neutrons and none of their antiparticles. A similar process happened at about 1 second after the Big Bang for electrons and positrons. After these annihilations, the remaining protons, neutrons and electrons were no longer moving relativistically and the energy density of the universe was dominated by photons - and to a lesser extent, neutrinos.

A few minutes into the expansion, the period known as Big Bang nucleosynthesis also began. Thanks to temperatures dropping to 1 billion kelvin and the energy densities dropping to about the equivalent of air, neutrons and protons began to combine to form the universe's first deuterium (a stable isotope of Hydrogen) and helium atoms. However, most of the Universe's protons remained uncombined as hydrogen nuclei.

After about 379,000 years, electrons combined with these nuclei to form atoms (again, mostly hydrogen), while the radiation decoupled from matter and continued to expand through space, largely unimpeded. This radiation is now known to be what constitutes the Cosmic Microwave Background (CMB), which today is the oldest light in the Universe.

As the CMB expanded, it gradually lost density and energy, and is currently estimated to have a temperature of 2.7260 ± 0.0013 K (-270.424 °C/ -454.763 °F ) and an energy density of (or ; 400-500 photons/cm ³). The CMB can be seen in all directions at a distance of roughly 13.8 billion light years, but estimates of its actual distance place it at about 46 billion light years from the center of the Universe.

Structure Epoch

Over the course of the several billion years that followed, the slightly denser regions of the almost uniformly distributed matter of the Universe began to become gravitationally attracted to each other. They therefore grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures that we regularly observe today.

This is what is known as the Structure Epoch, since it was during this time that the modern Universe began to take shape. This consists of visible matter distributed in structures of various sizes, ranging from stars and planets to galaxies, galaxy clusters, and super clusters - where matter is concentrated - that are separated by enormous gulfs containing few galaxies.

The details of this process depend on the amount and type of matter in the universe, with cold dark matter, warm dark matter, hot dark matter, and baryonic matter being the four suggested types. However, the Lambda-Cold Dark Matter model (Lambda-CDM), in which the dark matter particles moved slowly compared to the speed of light, is the considered to be the standard model of Big Bang cosmology, as it best fits the available data.

In this model, cold dark matter is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%. The Lambda refers to the Cosmological Constant, a theory originally proposed by Albert Einstein that attempted to show that the balance of mass-energy in the universe was static. In this case, it is associated with Dark Energy, which served to accelerate the expansion of the universe and keep its large-scale structure largely uniform.

Long-term Predictions for the Future of the Universe

Hypothesizing that the Universe had a starting point naturally gives rise to questions about a possible end point. If the Universe began as a tiny point of infinite density that started to expand, does that mean it will continue to expand indefinitely? Or will it one day run out of expansive force, and begin retreating inward until all matter crunches back into a tiny ball?

Answering this question has been a major focus of cosmologists ever since the debate about which model of the Universe was the correct one began. With the acceptance of the Big Bang Theory, but prior to the observation of Dark Energy in the 1990s, cosmologists had come to agree on two scenarios as being the most likely outcomes for our Universe.

In the first, commonly known as the "Big Crunch" scenario, the universe will reach a maximum size and then begin to collapse in on itself. This will only be possible if the mass density of the Universe is greater than the critical density. In other words, as long as the density of matter remains at or above a certain value (1-3 ×10⁻²⁶ kg of matter per m³), the Universe will eventually contract.

Alternatively, if the density in the universe were equal to or below the critical density, the expansion would slow down but never stop. In this scenario, known as the "Big Freeze", the Universe would go on until star formation eventually ceased with the consumption of all the interstellar gas in each galaxy. Meanwhile, all existing stars would burn out and become white dwarfs, neutron stars, and black holes.

Very gradually, collisions between these black holes would result in mass accumulating into larger and larger black holes. The average temperature of the universe would approach absolute zero, and black holes would evaporate after emitting the last of their Hawking radiation. Finally, the entropy of the universe would increase to the point where no organized form of energy could be extracted from it (a scenarios known as "heat death").

Modern observations, which include the existence of Dark Energy and its influence on cosmic expansion, have led to the conclusion that more and more of the currently visible universe will pass beyond our event horizon (i.e. the CMB, the edge of what we can see) and become invisible to us. The eventual result of this is not currently known, but "heat death" is considered a likely end point in this scenario too.

Other explanations of dark energy, called phantom energy theories, suggest that ultimately galaxy clusters, stars, planets, atoms, nuclei, and matter itself will be torn apart by the ever-increasing expansion. This scenario is known as the "Big Rip", in which the expansion of the Universe itself will eventually be its undoing.

History of the Big Bang Theory

The earliest indications of the Big Bang occurred as a result of deep-space observations conducted in the early 20th century. In 1912, American astronomer Vesto Slipher conducted a series of observations of spiral galaxies (which were believed to be nebulae) and measured their Doppler Redshift. In almost all cases, the spiral galaxies were observed to be moving away from our own.

In 1922, Russian cosmologist Alexander Friedmann developed what are known as the Friedmann equations, which were derived from Einstein's equations for general relativity. Contrary to Einstein's was advocating at the time with his a Cosmological Constant, Friedmann's work showed that the universe was likely in a state of expansion.

In 1924, Edwin Hubble's measurement of the great distance to the nearest spiral nebula showed that these systems were indeed other galaxies. At the same time, Hubble began developing a series of distance indicators using the 100-inch (2.5 m) Hooker telescope at Mount Wilson Observatory. And by 1929, Hubble discovered a correlation between distance and recession velocity - which is now known as Hubble's law.

And then in 1927, Georges Lemaitre, a Belgian physicist and Roman Catholic priest, independently derived the same results as Friedmann's equations and proposed that the inferred recession of the galaxies was due to the expansion of the universe. In 1931, he took this further, suggesting that the current expansion of the Universe meant that the father back in time one went, the smaller the Universe would be. At some point in the past, he argued, the entire mass of the universe would have been concentrated into a single point from which the very fabric of space and time originated.

These discoveries triggered a debate between physicists throughout the 1920s and 30s, with the majority advocating that the universe was in a steady state. In this model, new matter is continuously created as the universe expands, thus preserving the uniformity and density of matter over time. Among these scientists, the idea of a Big Bang seemed more theological than scientific, and accusations of bias were made against Lemaitre based on his religious background.

Other theories were advocated during this time as well, such as the Milne Model and the Oscillary Universe model. Both of these theories were based on Einstein's theory of general relativity (the latter being endorsed by Einstein himself), and held that the universe follows infinite, or indefinite, self-sustaining cycles.

After World War II, the debate came to a head between proponents of the Steady State Model (which had come to be formalized by astronomer Fred Hoyle) and proponents of the Big Bang Theory - which was growing in popularity. Ironically, it was Hoyle who coined the phrase "Big Bang" during a BBC Radio broadcast in March 1949, which was believed by some to be a pejorative dismissal (which Hoyle denied).

Eventually, the observational evidence began to favor Big Bang over Steady State. The discovery and confirmation of the cosmic microwave background radiation in 1965 secured the Big Bang as the best theory of the origin and evolution of the universe. From the late 60s to the 1990s, astronomers and cosmologist made an even better case for the Big Bang by resolving theoretical problems it raised.

These included papers submitted by Stephen Hawking and other physicists that showed that singularities were an inevitable initial condition of general relativity and a Big Bang model of cosmology. In 1981, physicist Alan Guth theorized of a period of rapid cosmic expansion (aka. the "Inflation" Epoch) that resolved other theoretical problems.

The 1990s also saw the rise of Dark Energy as an attempt to resolve outstanding issues in cosmology. In addition to providing an explanation as to the universe's missing mass (along with Dark Matter, originally proposed in 1932 by Jan Oort), it also provided an explanation as to why the universe is still accelerating, as well as offering a resolution to Einstein's Cosmological Constant.

Significant progress was made thanks to advances in telescopes, satellites, and computer simulations, which have allowed astronomers and cosmologists to see more of the universe and gain a better understanding of its true age. The introduction of space telescopes - such as the Cosmic Background Explorer (COBE), the Hubble Space Telescope, Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck Observatory - have also been of immeasurable value.

Today, cosmologists have fairly precise and accurate measurements of many of the parameters of the Big Bang Theory model, not to mention the age of the Universe itself. And it all began with the noted observation that massive stellar objects, many light years distant, were slowly moving away from us. And while we still are not sure how it will all end, we do know that on a cosmological scale, that won't be for a long, LONG time!

More Resources on the Big Bang Theory

We have many interesting articles about the Big Bang here at Universe Today. For instance, here is What is the Evidence of the Big Bang?, What Came Before the Big Bang?, A New Theory About Of The Universe's Creation, and What is Cosmic Background Radiation?

For more information, check out NASA's page on the Big Bang Theory. NASA's WMAP mission webpage, Big Bang Cosmology, and its "What is the Big Bang Theory?" also gives good introductions to the big bang theory. For a more detailed introduction, check out Ned Wright's Cosmology Tutorial.

Astronomy Cast has also has several relevant episodes on the subject. Here's Episode 137: Large Scale Structure of the Universe, Episode 123: Homogeneity, and Episode 58: Inflation.

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Big Bang Theory: Evolution of Our Universe - Universe Today

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How was our Universe created? How did it come to be the seemingly infinite place we know of today? And what will become of it, ages from now? These are the questions that have been puzzling philosophers and scholars since the beginning the time, and led to some pretty wild and interesting theories.

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http://www.space.com/13320-big-bang-universe-10-steps-explainer.html

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The Big Bang Theory

umich.edu/~gs265/bigbang.htm

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http://science.howstuffworks.com/innovation/science-questions/gravity-big-bang.htm

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the big bang theory is the theory that states that the universe started a long time ago before i was born.

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http://www.space.com/25126-big-bang-theory.html

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Origin of the theory:
http://www.pbs.org/wgbh/aso/databank/entries/dp27bi.html

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https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

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The Big Bang theory is an effort to explain what happened at the very beginning of our universe. Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe. The big bang theory is an effort to explain what happened during and after that moment.

According to the standard theory, our universe sprang into existence as "singularity" around 13.7 billion years ago. What is a "singularity" and where does it come from? Well, to be honest, we don't know for sure. Singularities are zones which defy our current understanding of physics. They are thought to exist at the core of "black holes." Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is actually squished into infinite density (a mathematical concept which truly boggles the mind). These zones of infinite density are called "singularities." Our universe is thought to have begun as an infinitesimally small, infinitely hot, infinitely dense, something - a singularity. Where did it come from? We don't know. Why did it appear? We don't know.

After its initial appearance, it apparently inflated (the "Big Bang"), expanded and cooled, going from very, very small and very, very hot, to the size and temperature of our current universe. It continues to expand and cool to this day and we are inside of it: incredible creatures living on a unique planet, circling a beautiful star clustered together with several hundred billion other stars in a galaxy soaring through the cosmos, all of which is inside of an expanding universe that began as an infinitesimal singularity which appeared out of nowhere for reasons unknown. This is the Big Bang theory.

Big Bang Theory - Common Misconceptions
There are many misconceptions surrounding the Big Bang theory. For example, we tend to imagine a giant explosion. Experts however say that there was no explosion; there was (and continues to be) an expansion. Rather than imagining a balloon popping and releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe.

Another misconception is that we tend to image the singularity as a little fireball appearing somewhere in space. According to the many experts however, space didn't exist prior to the Big Bang. Back in the late '60s and early '70s, when men first walked upon the moon, "three British astrophysicists, Steven Hawking, George Ellis, and Roger Penrose turned their attention to the Theory of Relativity and its implications regarding our notions of time. In 1968 and 1970, they published papers in which they extended Einstein's Theory of General Relativity to include measurements of time and space. 1, 2 According to their calculations, time and space had a finite beginning that corresponded to the origin of matter and energy." ³ The singularity didn't appear in space; rather, space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy - nothing. So where and in what did the singularity appear if not in space? We don't know. We don't know where it came from, why it's here, or even where it is. All we really know is that we are inside of it and at one time it didn't exist and neither did we.

Big Bang Theory - Evidence for the Theory
What are the major evidences which support the Big Bang theory?

First of all, we are reasonably certain that the universe had a beginning.

Second, galaxies appear to be moving away from us at speeds proportional to their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.

Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.

Finally, the abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins.

Big Bang Theory - The Only Plausible Theory?
Is the standard Big Bang theory the only model consistent with these evidences? No, it's just the most popular one. Internationally renown Astrophysicist George F. R. Ellis explains: "People need to be aware that there is a range of models that could explain the observations....For instance, I can construct you a spherically symmetrical universe with Earth at its center, and you cannot disprove it based on observations....You can only exclude it on philosophical grounds. In my view there is absolutely nothing wrong in that. What I want to bring into the open is the fact that we are using philosophical criteria in choosing our models. A lot of cosmology tries to hide that." ⁴

In 2003, Physicist Robert Gentry proposed an attractive alternative to the standard theory, an alternative which also accounts for the evidences listed above. ⁵ Dr. Gentry claims that the standard Big Bang model is founded upon a faulty paradigm (the Friedmann-lemaitre expanding-spacetime paradigm) which he claims is inconsistent with the empirical data. He chooses instead to base his model on Einstein's static-spacetime paradigm which he claims is the "genuine cosmic Rosetta." Gentry has published several papers outlining what he considers to be serious flaws in the standard Big Bang model. ⁶ Other high-profile dissenters include Nobel laureate Dr. Hannes Alfvйn, Professor Geoffrey Burbidge, Dr. Halton Arp, and the renowned British astronomer Sir Fred Hoyle, who is accredited with first coining the term "the Big Bang" during a BBC radio broadcast in 1950.

Big Bang Theory - What About God?
Any discussion of the Big Bang theory would be incomplete without asking the question, what about God? This is because cosmogony (the study of the origin of the universe) is an area where science and theology meet. Creation was a supernatural event. That is, it took place outside of the natural realm. This fact begs the question: is there anything else which exists outside of the natural realm? Specifically, is there a master Architect out there? We know that this universe had a beginning. Was God the "First Cause"? We won't attempt to answer that question in this short article. We just ask the question:

Does God Exist?

1. Steven W. Hawking, George F.R. Ellis, "The Cosmic Black-Body Radiation and the Existence of Singularities in our Universe," Astrophysical Journal, 152, (1968) pp. 25-36.

2. Steven W. Hawking, Roger Penrose, "The Singularities of Gravitational Collapse and Cosmology," Proceedings of the Royal Society of London, series A, 314 (1970) pp. 529-548.

3. Mark Eastman, Chuck Missler, The Creator: Beyond Time and Space, (1996) p. 11.

4. W. Wayt Gibbs, "Profile: George F. R. Ellis," Scientific American, October 1995, Vol. 273, No.4, p. 55.

5. See https://www.halos.com/reports/ext-2003-022.pdf

6. See https://www.halos.com/reports/arxiv-1998-rosetta.pdf and https://www.halos.com/reports/ext-2003-021.pdf; see also https://www.halos.com/reports/arxiv-1998-redshift.pdf and https://www.halos.com/reports/arxiv-1998-affirmed.pdf

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The Big Bang theory is an effort to explain what happened at the very beginning of our universe. Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe.

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http://www.universetoday.com/54756/what-is-the-big-bang-theory/

https://www.quora.com/Why-is-the-Big-Bang-theory-important

http://www.big-bang-theory.com/

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http://phys.org/news/2014-11-gravity-universe-big.html

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http://www.forbes.com/sites/startswithabang/2016/05/05/top-10-facts-about-the-big-bang-theory/#253cc57bdc74

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Here's another video explaining the big bang.
https://www.youtube.com/watch?v=wNDGgL73ihY

# data[].attributes.body
http://www.big-bang-theory.com/
https://www.youtube.com/watch?v=uabNtlLfYyU

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http://science.nationalgeographic.com/science/space/universe/origins-universe-article/

# data[].attributes.body
http://www.physicsoftheuniverse.com/topics_bigbang_antimatter.html

# data[].attributes.body
http://www.space.com/25126-big-bang-theory.html

# data[].attributes.body
http://www.universetoday.com/54756/what-is-the-big-bang-theory/

# data[].attributes.body
http://www.space.com/25126-big-bang-theory.html

https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

# data[].attributes.body
http://study.com/academy/lesson/evidence-for-the-big-bang-theory-background-radiation-red-shift-and-expansion.html

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BBC - GCSE Bitesize: The Big Bang theory

# data[].attributes.attachment_link.description
A secondary school revision resource for OCR GCSE Physics about energy resources and the Big Bang - with higher tier

# data[].attributes.body
http://www.universetoday.com/54756/what-is-the-big-bang-theory/

# data[].attributes.body
This can work for the last question.

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A clown walks on stage. Maybe he pulls a cowboy pistol from a holster. Maybe he pops a balloon. Either way, the punch line is unavoidable: His pants fall down. Children roar with laughter, but this is far more than a mere vaudevillian sight gag. This is one of the four fundamental forces of nature in action.

Yes, it's gravity -- a force so constant and ubiquitous that we rarely notice it. Yet without gravity, the universe as we know it could not exist. As such, gravity plays a starring role in the theory of the big bang, the immense expansion event from which the universe's billions of galaxies herald.

According to Sir Isaac Newton's law of universal gravitation, gravity is an attractive force that acts on every particle of matter in the universe. The strength of the attraction depends on distance and mass however. If they're close enough, two particles of cosmic dust will gravitate toward each other. Meanwhile, the gravitational force of a planet will pull on objects much farther away.

In the early 20th century, physicist Albert Einstein built on Newton's findings with his general theory of relativity, which, among other things, explained gravity not as a force but as a distortion in the shape of space-time. A particularly massive object like a star warps both the time and space around it. Time itself passes measurably slower in close proximity to such an object and curves the otherwise straight path of speeding light waves. Gravity dictates the structure of the universe, from the way cosmic bodies form to the way they orbit more massive planets or stars.

Einstein also proposed that the universe began as a singularity, a point with zero volume and infinite density containing all the matter of the universe. Then the big bang occurred, rapidly expanding all that matter with enough ferocity to overpower the inward pull of gravity. Einstein also predicted that we'd be able to tell gravity was present during those early moments, thanks to gravitational waves (or changes in a gravitational field). All the resulting gas and dust eventually formed into the universe we know today due to gravity as well.

Gravity is one of the four forces of nature, along with electromagnetism, strong force and weak force. All of these forces are tied up in the big bang theory. Furthermore, Einstein's groundbreaking theories about the nature of gravity were central to the understanding of the universe he presented with general relativity.

So remember: Gravity isn't just the force that makes a clown's pants fall down. It's a key aspect of the universe, all the way back to the big bang.

Related HowStuffWorks Articles

More Great Links

Sources

"The Big Bang." NASA. April 5, 2010. (June 17, 2010)http://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang/

Lightman, Alan."Relativity and the Cosmos." NOVA. June 2005. (June 17, 2010)http://www.pbs.org/wgbh/nova/einstein/relativity/

Silvis, Jeff and Mark Kowitt. "The Four Forces of Nature." NASA. Dec. 1, 2005. (June 17, 2010)http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980127c.html

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What does gravity have to do with the big bang?

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A clown walks on stage. Maybe he pulls a cowboy pistol from a holster. Maybe he pops a balloon. Either way, the punch line is unavoidable: His pants fall down. Children roar with laughter, but this is far more than a mere vaudevillian sight gag.

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https://www.exploratorium.edu/origins/cern/ideas/bang.html

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dot com

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https://en.wikipedia.org/wiki/Big_Bang

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http://sciencelearn.org.nz/Contexts/Just-Elemental/Sci-Media/Video/What-is-the-Big-Bang-theory

# data[].attributes.body
http://umich.edu/~gs265/bigbang.htm

https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

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#5 Website

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A clown walks on stage. Maybe he pulls a cowboy pistol from a holster. Maybe he pops a balloon. Either way, the punch line is unavoidable: His pants fall down. Children roar with laughter, but this is far more than a mere vaudevillian sight gag. This is one of the four fundamental forces of nature in action.

Yes, it's gravity -- a force so constant and ubiquitous that we rarely notice it. Yet without gravity, the universe as we know it could not exist. As such, gravity plays a starring role in the theory of the big bang, the immense expansion event from which the universe's billions of galaxies herald.

According to Sir Isaac Newton's law of universal gravitation, gravity is an attractive force that acts on every particle of matter in the universe. The strength of the attraction depends on distance and mass however. If they're close enough, two particles of cosmic dust will gravitate toward each other. Meanwhile, the gravitational force of a planet will pull on objects much farther away.

In the early 20th century, physicist Albert Einstein built on Newton's findings with his general theory of relativity, which, among other things, explained gravity not as a force but as a distortion in the shape of space-time. A particularly massive object like a star warps both the time and space around it. Time itself passes measurably slower in close proximity to such an object and curves the otherwise straight path of speeding light waves. Gravity dictates the structure of the universe, from the way cosmic bodies form to the way they orbit more massive planets or stars.

Einstein also proposed that the universe began as a singularity, a point with zero volume and infinite density containing all the matter of the universe. Then the big bang occurred, rapidly expanding all that matter with enough ferocity to overpower the inward pull of gravity. Einstein also predicted that we'd be able to tell gravity was present during those early moments, thanks to gravitational waves (or changes in a gravitational field). All the resulting gas and dust eventually formed into the universe we know today due to gravity as well.

Gravity is one of the four forces of nature, along with electromagnetism, strong force and weak force. All of these forces are tied up in the big bang theory. Furthermore, Einstein's groundbreaking theories about the nature of gravity were central to the understanding of the universe he presented with general relativity.

So remember: Gravity isn't just the force that makes a clown's pants fall down. It's a key aspect of the universe, all the way back to the big bang.

Related HowStuffWorks Articles

More Great Links

Sources

"The Big Bang." NASA. April 5, 2010. (June 17, 2010)http://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang/

Lightman, Alan."Relativity and the Cosmos." NOVA. June 2005. (June 17, 2010)http://www.pbs.org/wgbh/nova/einstein/relativity/

Silvis, Jeff and Mark Kowitt. "The Four Forces of Nature." NASA. Dec. 1, 2005. (June 17, 2010)http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980127c.html

# data[].attributes.attachment_link.title
What does gravity have to do with the big bang?

# data[].attributes.attachment_link.description
A clown walks on stage. Maybe he pulls a cowboy pistol from a holster. Maybe he pops a balloon. Either way, the punch line is unavoidable: His pants fall down. Children roar with laughter, but this is far more than a mere vaudevillian sight gag.

# data[].attributes.body
http://www.big-bang-theory.com/

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http://the-big-bang-theory.com/

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check out http://www.big-bang-theory.com/
also check out https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang
and http://www.universetoday.com/54756/what-is-the-big-bang-theory/#

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http://www.universetoday.com/54756/what-is-the-big-bang-theory/

# data[].attributes.body
http://spaceplace.nasa.gov/big-bang/en/

# data[].attributes.body
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

# data[].attributes.body
http://umich.edu/~gs265/bigbang.htm

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Watch Exploring the Big Bang Theory Clip - The Universe | HISTORY

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Watch the Exploring the Big Bang Theory video clip of HISTORY's series The Universe'. Find this and many more videos only on HISTORY.

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http://www.big-bang-theory.com/

# data[].attributes.body
http://umich.edu/~gs265/bigbang.htm

# data[].attributes.body
http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway/energy_resources/big_bangrev2.shtml

# data[].attributes.body
http://science.nationalgeographic.com/science/space/universe/origins-universe-article/

# data[].attributes.body
http://www.space.com/25126-big-bang-theory.html

http://www.big-bang-theory.com

http://science.howstuffworks.com/innovation/science-questions/gravity-big-bang.htm

# data[].attributes.body
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

http://spaceplace.nasa.gov/big-bang/en/

# data[].attributes.body
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

# data[].attributes.body
http://www.big-bang-theory.com/

# data[].attributes.body
http://map.gsfc.nasa.gov/universe/bb_theory.html

# data[].attributes.body
http://www.big-bang-theory.com/

# data[].attributes.attachment_link.description
The Big Bang Theory explains how the universe began with an infinitely hot and dense single point that inflated to form the ever-expanding cosmos we see today.

# data[].attributes.body
http://www.universetoday.com/54756/what-is-the-big-bang-theory/

# data[].attributes.body
http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway/energy_resources/big_bangrev1.shtml

# data[].attributes.attachment_link.title
BBC - GCSE Bitesize: The Big Bang theory

# data[].attributes.attachment_link.description
A secondary school revision resource for OCR GCSE Physics about energy resources and the Big Bang - with higher tier

# data[].attributes.body
This is a good website for the first question.
http://www.space.com/25126-big-bang-theory.html

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http://science.nationalgeographic.com/science/space/universe/origins-universe-article/

# data[].attributes.body
http://physics.about.com/od/astronomy/f/BigBang.htm

# data[].attributes.body
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

# data[].attributes.body
http://spaceplace.nasa.gov/big-bang/en/
https://map.gsfc.nasa.gov/universe/bb_theory.html

# data[].attributes.body
http://spaceplace.nasa.gov/big-bang/en/

http://www.schoolsobservatory.org.uk/astro/cosmos/bb_evid

http://umich.edu/~gs265/bigbang.htm

http://www.livescience.com/32278-was-the-big-bang-really-an-explosion.html

Video:
https://www.youtube.com/watch?v=OdTTwtVcYjU

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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.

What Is the Big Bang Theory?

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.

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.

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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.

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Good for all except 2nd question
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

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https://www.esa.int/esaKIDSen/SEMSZ5WJD1E_OurUniverse_0.html

https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

http://umich.edu/~gs265/bigbang.htm

http://science.nationalgeographic.com/science/space/universe/origins-universe-article/

http://science.howstuffworks.com/innovation/science-questions/gravity-big-bang.htm

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http://www.schoolsobservatory.org.uk/astro/cosmos/bb_evid

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NASA website for Big Bang Theory

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Astronomers combine mathematical models with observations to develop workable theories of how the Universe came to be. The mathematical underpinnings of the Big Bang theory include Albert Einstein's general theory of relativity along with standard theories of fundamental particles. Today NASA spacecraft such as the Hubble Space Telescope and the Spitzer Space Telescope continue measuring the expansion of the Universe. One of the goals has long been to decide whether the Universe will expand forever, or whether it will someday stop, turn around, and collapse in a "Big Crunch?"

Background Radiation

According to the theories of physics, if we were to look at the Universe one second after the Big Bang, what we would see is a 10-billion degree (° K) sea of neutrons, protons, electrons, anti-electrons (positrons), photons, and neutrinos. Then, as time went on, we would see the Universe cool, the neutrons either decaying into protons and electrons or combining with protons to make deuterium (an isotope of hydrogen). As it continued to cool, it would eventually reach the temperature where electrons combined with nuclei to form neutral atoms. Before this "recombination" occurred, the Universe would have been opaque because the free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds. But when the free electrons were absorbed to form neutral atoms, the Universe suddenly became transparent. Those same photons - the afterglow of the Big Bang known as cosmic background radiation - can be observed today.

Missions Study Cosmic Background Radiation

NASA has launched two missions to study the cosmic background radiation, taking "baby pictures" of the Universe only 400,000 years after it was born. The first of these was the Cosmic Background Explorer (COBE). In 1992, the COBE team announced that they had mapped the primordial hot and cold spots in cosmic background radiation. These spots are related to the gravitational field in the early Universe and form the seeds of the giant clusters of galaxies that stretch hundreds of millions of light years across the Universe. This work earned NASA's Dr. John C. Mather and George F. Smoot of the University of California the 2006 Nobel Prize for Physics.

The second mission to examine the cosmic background radiation was the Wilkinson Microware Anisotropy Probe (WMAP). With greatly improved resolution compared to COBE, WMAP surveyed the entire sky, measuring temperature differences of the microwave radiation that is nearly uniformly distributed across the Universe. The picture shows a map of the sky, with hot regions in red and cooler regions in blue. By combining this evidence with theoretical models of the Universe, scientists have concluded that the Universe is "flat," meaning that, on cosmological scales, the geometry of space satisfies the rules of Euclidean geometry (e.g., parallel lines never meet, the ratio of circle circumference to diameter is pi, etc).

A third mission, Planck, led by the European Space Agency with significant participation from NASA, was. launched in 2009. Planck is making the most accurate maps of the microwave background radiation yet. With instruments sensitive to temperature variations of a few millionths of a degree, and mapping the full sky over 9 wavelength bands, it measures the fluctuations of the temperature of the CMB with an accuracy set by fundamental astrophysical limits.

Inflation

One problem that arose from the original COBE results, and that persists with the higher-resolution WMAP data, was that the Universe was too homogeneous. How could pieces of the Universe that had never been in contact with each other have come to equilibrium at the very same temperature? This and other cosmological problems could be solved, however, if there had been a very short period immediately after the Big Bang where the Universe experienced an incredible burst of expansion called "inflation." For this inflation to have taken place, the Universe at the time of the Big Bang must have been filled with an unstable form of energy whose nature is not yet known. Whatever its nature, the inflationary model predicts that this primordial energy would have been unevenly distributed in space due to a kind of quantum noise that arose when the Universe was extremely small. This pattern would have been transferred to the matter of the Universe and would show up in the photons that began streaming away freely at the moment of recombination. As a result, we would expect to see, and do see, this kind of pattern in the COBE and WMAP pictures of the Universe.

But all this leaves unanswered the question of what powered inflation. One difficulty in answering this question is that inflation was over well before recombination, and so the opacity of the Universe before recombination is, in effect, a curtain drawn over those interesting very early events. Fortunately, there is a way to observe the Universe that does not involve photons at all. Gravitational waves, the only known form of information that can reach us undistorted from the instant of the Big Bang, can carry information that we can get no other way. Several missions are being considered by NASA and ESA that will look for the gravitational waves from the epoch of inflation.

Dark Energy

During the years following Hubble and COBE, the picture of the Big Bang gradually became clearer. But in 1996, observations of very distant supernovae required a dramatic change in the picture. It had always been assumed that the matter of the Universe would slow its rate of expansion. Mass creates gravity, gravity creates pull, the pulling must slow the expansion. But supernovae observations showed that the expansion of the Universe, rather than slowing, is accelerating. Something, not like matter and not like ordinary energy, is pushing the galaxies apart. This "stuff" has been dubbed dark energy, but to give it a name is not to understand it. Whether dark energy is a type of dynamical fluid, heretofore unknown to physics, or whether it is a property of the vacuum of empty space, or whether it is some modification to general relativity is not yet known.

Recent Discoveries

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The night sky presents the viewer with a picture of a calm and unchanging Universe. So when scientists noticed that the Universe is in fact expanding at enormous speed this was revolutionary. Astronomers noted that galaxies outside our own Milky Way were all moving away from us, each at a speed proportional to its distance from us.

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This is a short, 6 minute video explaining the Big Bang Theory. It explains basically everything that happened in the Big Bang Theory that we know of.

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The Beginning of Everything -- The Big Bang

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http://science.howstuffworks.com/innovation/science-questions/gravity-big-bang.htm

# data[].attributes.body
https://www.esa.int/esaKIDSen/SEMSZ5WJD1E_OurUniverse_0.html

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http://www.big-bang-theory.com/

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https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

# data[].attributes.body
http://www.space.com/25126-big-bang-theory.html

http://science.howstuffworks.com/innovation/science-questions/gravity-big-bang.htm

https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

# data[].attributes.body
http://www.big-bang-theory.com/

http://www.schoolsobservatory.org.uk/astro/cosmos/bb_evid

http://www.universetoday.com/54756/what-is-the-big-bang-theory/

http://creationtoday.org/the-big-bang-theory/

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http://www.space.com/25126-big-bang-theory.html

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Share links with  your classmates by clicking on the plus sign at the bottom of a box. 

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Share links with  your classmates by clicking on the plus sign at the bottom of a box. 

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The Big Bang Theory explains how the universe began with an infinitely hot and dense single point that inflated to form the ever-expanding cosmos we see today.

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1. What is the Big Bang Theory?

2. Why is this theory important?

3. When did the Big Bang take place?

4. What proof do astronomers have to support the theory?

5. What role does gravity play in the Big Bang theory?

Answer the questions above completely, and thoroughly. Go above one word or one sentence answer.  Numbers 2- 5 should have many thoughts to show what you have learned.  You may use bullet points, drawings, words or diagrams to show your work.