Big Bang Theory?????

Question

Ok.... i was away for the last few science lessons and we started a new topic, the Big Bang Theory, and nobody will explain it to me.

Can anybody give me an overview of the Big Bang theory???

Answer 1

The Big Bang is the cosmological model of the universe that is best supported by all lines of scientific evidence and observation. The essential idea is that the universe has expanded from a primordial hot and dense initial condition at some finite time in the past and continues to expand to this day. The framework for the model relies on Albert Einstein's General Relativity as formulated by Alexander Friedmann. After Edwin Hubble discovered in 1929 that the distances to far away galaxies were generally proportional to their redshifts, this observation was taken to indicate that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point. The farther away, the higher the apparent velocity.[1] If the distance between galaxy clusters is increasing today, everything must have been closer together in the past. This idea has been considered in detail back in time to extreme densities and temperatures, and large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of the theory. But these accelerators can only probe so far into such high energy regimes. Without any evidence associated with the earliest instant of the expansion, the Big Bang theory cannot and does not provide any explanation for such an initial condition. The theory accurately explains the general evolution of the universe since that instant.

A major success of the theory is its ability to account for the comparative abundance of the elements we find around us, which if you look beyond Earth is mostly hydrogen and helium. The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the universe, as logically and quantitatively detailed according to Big Bang nucleosynthesis and well described in Steven Weinberg's classic The First Three Minutes.

The term 'Big Bang' was apparently first coined by Fred Hoyle in a derisory statement seeking to belittle the credibility of the theory that he did not believe to be true. Ironically, Hoyle helped considerably in the effort to figure out the nuclear pathway for building certain heavier elements from lighter ones. At any rate, after the discovery of the cosmic microwave background in 1964, and especially when its collective frequencies sketched out a blackbody curve, most scientists were fairly convinced by the evidence that some Big Bang scenario must have occurred.

Answer 2

there was a bang at the centre of the universe and the planets move further and further away till there is a galaxy/ mulitple galaxies

Answer 3

Nonsense. No such things. Rumor.

Answer 4

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.

The origin of the Big Bang theory can be credited to Edwin Hubble. Hubble made the observation that the universe is continuously expanding. He discovered that a galaxys velocity is proportional to its distance. Galaxies that are twice as far from us move twice as fast. Another consequence is that the universe is expanding in every direction. This observation means that it has taken every galaxy the same amount of time to move from a common starting position to its current position. Just as the Big Bang provided for the foundation of the universe, Hubbles observations provided for the foundation of the Big Bang theory.

Since the Big Bang, the universe has been continuously expanding and, thus, there has been more and more distance between clusters of galaxies. This phenomenon of galaxies moving farther away from each other is known as the red shift. As light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to wavelengths being stretched.

In addition to the understanding of the velocity of galaxies emanating from a single point, there is further evidence for the Big Bang. In 1964, two astronomers, Arno Penzias and Robert Wilson, in an attempt to detect microwaves from outer space, inadvertently discovered a noise of extraterrestrial origin. The noise did not seem to emanate from one location but instead, it came from all directions at once. It became obvious that what they heard was radiation from the farthest reaches of the universe which had been left over from the Big Bang. This discovery of the radioactive aftermath of the initial explosion lent much credence to the Big Bang theory.

Even more recently, NASAs COBE satellite was able to detect cosmic microwaves eminating from the outer reaches of the universe. These microwaves were remarkably uniform which illustrated the homogenity of the early stages of the universe. However, the satillite also discovered that as the universe began to cool and was still expanding, small fluctuations began to exist due to temperature differences. These flucuatuations verified prior calculations of the possible cooling and development of the universe just fractions of a second after its creation. These fluctuations in the universe provided a more detailed description of the first moments after the Big Bang.

Now that an attempt has been made to grapple with the theory of the Big Bang, the next logical question to ask would be what happened afterward? In the minuscule fractions of the first second after creation what was once a complete vacuum began to evolve into what we now know as the universe. In the very beginning there was nothing except for a plasma soup. What is known of these brief moments in time, at the start of our study of cosmology, is largely conjectural. However, science has devised some sketch of what probably happened, based on what is known about the universe today.

Immediately after the Big Bang, as one might imagine, the universe was tremendously hot as a result of particles of both matter and antimatter rushing apart in all directions. As it began to cool, at around 10^-43 seconds after creation, there existed an almost equal yet asymmetrical amount of matter and antimatter. As these two materials are created together, they collide and destroy one another creating pure energy. Fortunately for us, there was an asymmetry in favor of matter. As a direct result of an excess of about one part per billion, the universe was able to mature in a way favorable for matter to persist. As the universe first began to expand, this discrepancy grew larger. The particles which began to dominate were those of matter. They were created and they decayed without the accompaniment of an equal creation or decay of an antiparticle.

As the universe expanded further, and thus cooled, common particles began to form. These particles are called baryons and include photons, neutrinos, electrons and quarks would become the building blocks of matter and life as we know it. During the baryon genesis period there were no recognizable heavy particles such as protons or neutrons because of the still intense heat. At this moment, there was only a quark soup. As the universe began to cool and expand even more, we begin to understand more clearly what exactly happened.

After the universe had cooled to about 3000 billion degrees Kelvin, a radical transition began which has been likened to the phase transition of water turning to ice. Composite particles such as protons and neutrons, called hadrons, became the common state of matter after this transition. Still, no matter more complex could form at these temperatures. Although lighter particles, called leptons, also existed, they were prohibited from reacting with the hadrons to form more complex states of matter. These leptons, which include electrons, neutrinos and photons, would soon be able to join their hadron kin in a union that would define present-day common matter.

After about one to three minutes had passed since the creation of the universe, protons and neutrons began to react with each other to form deuterium, an isotope of hydrogen. Deuterium, or heavy hydrogen, soon collected another neutron to form tritium. Rapidly following this reaction was the addition of another proton which produced a helium nucleus. Scientists believe that there was one helium nucleus for every ten protons within the first three minutes of the universe. After further cooling, these excess protons would be able to capture an electron to create common hydrogen. Consequently, the universe today is observed to contain one helium atom for every ten or eleven atoms of hydrogen.

While it is true that much of this information is speculative, as the universe ages we are able to become increasingly confident in our knowledge of its history. By studying the way in which the universe exists today it is possible to learn a great deal about its past. Much effort has gone into understanding the formation and number of baryons present today. Through finding answers to these modern questions, it is possible to trace their role in the universe back to the Big Bang. Subsequently, by studying the formation of simple atoms in the laboratory we can make some educated guesses as to how they formed originally. Only through further research and discovery will it be possible to completely understand the creation of the universe and its first atomic structures, however, maybe we will never know for sure.

Answer 5

A theory is a collection of equations (verified by observations) that are used to explain an event or an operation.  It is often based on a hypothesis.

The Primordial Atom Hypothesis:

Hubble (the astronomer, the space telescope is named in his honor) saw that distant galaxies all appear to move away from each other (and form us, since we too are in a Galaxy) and that the speed of recession was linked to the distance.  Twice as far = twice as fast, etc.

Lemaitre calculated that if you ran the clock backwards, there would have been a time when all galaxies were all in the same spot.  He formulated the hypothesis:  the universe began with all its content (assumed to be matter, at the time) in one indivisible and very dense mass (an 'atom' using the original Greek meaning of the word, not the modern chemical sense).

Scientists began adding knowledge from all branches of science (physics, chemistry...) to see if this idea made sense.  Actually, at the time, most scientists wanted to prove it wrong.  They did not like the new theory because it was weird and went against a fundamental quest, that of the Perfect Cosmological Principle (on the very large scale, the universe looks the same everywhere, the same in all directions and the same for all times).

Even Einstein did not want the universe to be expanding.  He had developed mathematical models of how a universe would behave in the presence of mass (to model gravitation for this theory of relativity), and his models showed that the universe would expand or contract (depending on the density of the mass).  Believing this to be a flaw, he added a "cosmological constant" to prevent expansion in his model.  

Faced with more and more evidence, Einstein finally removed the constant, calling it the worst blunder of his life.

Meanwhile Fred Hoyle (regarded as the best astrophysicist at the time) had developed the Steady State theory which allowed the universe to be expanding, yet to still keep the Perfect Cosmological Principle.

All this was going on in the 1920s, 30s and 40s.  Generations of scientists grew up facing two theories, one of which (Steady State) was much easier to work with, was much preferred by most scientist and was supported by Fred Hoyle, the most famous astrophysicist (and he did deserve the recognition -- he was very good).

The other asked them to accept very strange facts, not the least of which was that the universe did have a beginning and that it was very different in the past (at the time, they saw no sign of this).  Plus, the original hypothesis was the work of a priest, which raised suspicion that the whole thing was made up just to try and justify the existence of a Creator.  To the end of his life, Hoyle still believed that the big advantage of the Steady State theory is that it did not need a god to start things off.

Overview of what the Theory says about the history of the universe.

The universe began in an unbound state of energy density (a.k.a. temperature) and expanded.  As it expanded, it cooled.  Thing began to 'condense' out of the energy as it cooled.  First the forces themselves (electromagnetic, weak nuclear, strong nuclear) in the first second.  Then matter in the form of particles (quarks, electrons...) and later light atoms like hydrogen, deuterium and helium (with a pinch of Lithium, Beryllium) but not much anything else, as the temperature had too rapidly dropped too much.  This part only lasted 3 minutes.

As the temperature continued to drop (it is still very high), the particles are kept apart by the energy:  neutral atoms and molecules cannot be formed, because as soon an an electron would try to orbit a proton, it would get knocked off by a photon (at that temperature, photons are very strong).

This lasts for 300,000 years.  After that length of time, the temperature has dropped to around 3000 K (around 5000 F).

At that temperature, the photons are no longer strong enough to keep the electrons out of orbit.  Neutral atoms can form.  Liberated from all the free electrons (and protons), the universe suddenly becomes transparent.  All the light in the universe is released in one big burst.

Today, we still "see" this burst as the Cosmological Microwave Background radiation.  We "see" it with radio telescopes because the wavelengths of the light has been stretched by expansion that continued since then.

Since the Big Bang theory is about the whole universe, we have to rely on other theories to explain the formation of heavier atoms (like Carbon, Nitrogen and Oxygen formed inside the first stars) and of stellar systems.

Fred Hoyle did prepare a lot of these other theories and he showed that they could work just as well under any (acceptable) cosmological theory.  So the Big Bang theory does not explain how Earth was formed (simply because Earth is too small for the Big Bang theory to explain it -- the theory deals with the whole universe and the energy it contains).

The Big Bang theory does NOT even try to explain why the universe was that way at the beginning or what was there before.  Einstein's models (separate model for a separate theory of space-time) show that time itself does not exist in a universe without matter.  From that, many people (including myself) say that time itself did not exist "before" the beginning of the universe -- in other words, there is no "before" before the Big Bang.

Another thing that the Big Bang theory shows us is that we cannot go back all the way to time = zero.  We get stuck at the Planck Time (very very close to zero, but NOT zero); at that time, the universe would have been so hot that every single point would have been a black hole.  It is impossible (for now, anyways) to understand what could have existed before that moment.

The name itself evokes the idea of an explosion, but there was no explosion.  Nothing exploded into anything else.  It was simply an expansion of the entire universe (an expansion that still continues today).

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Fred Hoyle never hid the fact that he was a convinced atheist.  He hated the idea that the universe could have been created by a Creator and just the idea that the Big Bang theory allowed that possibility was enough to make him fight it.

Gentry based his on Einstein's "static space-time paradigm" meaning, the model with the artificial cosmological constant added in (which Einstein himself called his greatest blunder).

We don't really discuss Gentry's when we discuss cosmological models, since it is based on a blunder).

Others may have a better case (even though they are not yet taken seriously).  In MOND (MOdified Newtonian Dynamics), the basic idea -- it is actually a bit more complicated -- is that our gravitational equation is not quite right:

F = G * M * m / d^x

where x is taken as exactly 2

What they are saying is that maybe x is very very close to 2, but not exactly 2.  IF (a big IF) this is true, a carefully selected value for x could eliminate the need for dark matter and even (maybe perhaps) the dark energy that has been invented to explain the accelerating expansion and to bring Omega close to 1.

Since Relativity is an extension of the gravitational theory, the new value for x would be extended into Relativity so that it would continue to be valid.

The biggest problem for now is that our observations cannot be made precise enough to find any difference between 2 and x.

Answer 6

The Big Bang is the cosmological model of the universe that is best supported by all lines of scientific evidence and observation. The essential idea is that the universe has expanded from a primordial hot and dense initial condition at some finite time in the past and continues to expand to this day. The framework for the model relies on Albert Einstein's General Relativity as formulated by Alexander Friedmann. After Edwin Hubble discovered in 1929 that the distances to far away galaxies were generally proportional to their redshifts, this observation was taken to indicate that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point. The farther away, the higher the apparent velocity.[1] If the distance between galaxy clusters is increasing today, everything must have been closer together in the past. This idea has been considered in detail back in time to extreme densities and temperatures, and large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of the theory. But these accelerators can only probe so far into such high energy regimes. Without any evidence associated with the earliest instant of the expansion, the Big Bang theory cannot and does not provide any explanation for such an initial condition. The theory accurately explains the general evolution of the universe since that instant.

A major success of the theory is its ability to account for the comparative abundance of the elements we find around us, which if you look beyond Earth is mostly hydrogen and helium. The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the universe, as logically and quantitatively detailed according to Big Bang nucleosynthesis and well described in Steven Weinberg's classic The First Three Minutes.

The term 'Big Bang' was apparently first coined by Fred Hoyle in a derisory statement seeking to belittle the credibility of the theory that he did not believe to be true.[2] Ironically, Hoyle helped considerably in the effort to figure out the nuclear pathway for building certain heavier elements from lighter ones. At any rate, after the discovery of the cosmic microwave background in 1964, and especially when its collective frequencies sketched out a blackbody curve, most scientists were fairly convinced by the evidence that some Big Bang scenario must have occurred.

Basically it's all there.

Answer 7

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 Alfvén, 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.

Answer 8

I wrote exactly such a thing a while back, in fairly easy to understand terms, which can be found at http://www.associatedcontent.com/article...