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The Big Bang 2008

Page history last edited by PBworks 16 years ago

The Big Bang

 

History of the Big Bang Theory:

 

The term "Big Bang" actually came from Fred Hoyle, who did not believe the theory and wished to discredit the idea, but the name stuck. (Fred Hoyle believed in the Steady State model of the universe, the competition of the Big Bang theory in the mid-twentieth century.) The Big Bang theory is now the nearly universally accepted view of the universe.

 

What is the Big Bang?

 

The Big Bang Theory is really the affectionate term for a theory about how the universe as we know it began. There wasn't actually an explosion, or "bang", as the name suggests, just a rapid expansion of space. This theory is that everything started off in an extremely dense, hot state; the entire universe was pushed into a particle of a size smaller than an atom. From that point, about 13.7 billion years ago, the universe rapidly inflated in only a fraction of a second, and began to expand and cool. This led to such things as the formation of stars and galaxies, 400,000 years after the "big bang." The universe has continued to expand and cool, leading to theories on what will happen next.

 

Several Theories of Possible Outcomes:

1. The "Big Crunch": If the mass density of the universe is greater then the critical mass, then it will eventually get to its maximum size. After it reaches that point the Universe will begin to collapse back to its original hot, dense state.

2. The "Big Chill" or "Heat Death": If the mass density is equal or less then the critical mass, the expansion of the universe will slow down, but never stop. The formation of stars will cease. This is because all the intersteller gas will eventually run out. The result of this will be all the stars burning up, leaving only white dwarfs, neutron stars and black holes. Over a long period of time, the black holes will collide and the average temperature will approach absolute zero. Eventually the entropy of the universe will increase until there is no organized for of energy that can be used.

3. The "Big Rip": All the matter in the universe while be torn apart due to the expansion of the universe. First the galaxies will rip apart. Next the gravity in our solar system will no longer be able to keep it together, and the solar systems will fall apart. Next, all the stars and plants will start to come apart, until finally, even atoms are destroyed.

 

Megan G. and Leah E.

 

 

Big Bang Timeline

 

This is a close look at each split second phase, or epoch, of the Big Bang.

 

The Planck Epoch is a barrier beyond which we cannot even begin to probe. This barrier exists for several reasons:

  1. During the Planck Epoch, all four fundamental forces were equally powerful. Therefore, the normal rules of physics do not apply.
  2. Planck Time (5.4 * 10-44 s) and Planck Length (1.6 * 10-33 cm, or the distance light travels in one Planck Time) are the smallest existing measurements, and we cannot hypothesize beyond them.
  3. If we try to understand the Planck Epoch with General Relativity, we end up with the Planck barrier. If we try to understand it with Quantum Physics, the idea of a singularity becomes impossible. Unfortunately, no theory exists that combines General Relativity and Quantum Physics.

The term symmetry breaking refers to a tiny fluctuation causing a tremendous change in a system, destroying its symmetry. This occurred during the Planck Epoch, where infinitesimally small chaotic movements eventually caused gravity to lose influence and become a unique force. If it had not been for this symmetry breaking, the universe would be homogenous, and we would not exist.

 

Grand Unification Epoch - 10-43 to 10-36 seconds

The Grand Unification Epoch is not easily understood, and cannot be accurately portrayed due to the intense heat (1029 K at the very least!) and the intense pressure (the universe was so small at this point that it would be invisible to human eyes). This epoch was marked by the seperation of gravity from the homogenous force that dominated the very early universe. Now gravity and a unified force known as the electronuclear force held power. Gravity was the weaker of the two, as it is today. Due to the combined forces, mass, charge, and many other characteristics of particles were then meaningless.

The Grand Unification Epoch ended when the strong interaction split off of the electronuclear force. In addition, temperatures began to cool, and the many exotic particles that existed during it began to decay. One peculiar molecule, the X Boson, decayed in a very unusual way. It either became matter or antimatter, but never matter and antimatter. Asymmetry in its decay patterns and the fact that antimatter (the X Boson) decayed into matter could account for the lack of antimatter in the universe today (for more information, see Antimatter).

 

Electroweak Epoch - 10-36 to 10-12 seconds

The Electroweak Epoch was ruled by gravity, the strong interaction, and the electroweak force, a combination of the weak interaction and electromagnetism. The electroweak force allowed the synthesis of many exotic particles, such as W and Z bosons. In fact, the end of this epoch was marked by the decay of these bosons. With these bosons, the avatars of the weak interaction, no longer able to exist for more than an instant, the weak interaction became a much shorter and weaker force than electromagnetism, splitting them.

The Electroweak Epoch also housed the cosmic inflation.

 

Inflationary Epoch - 10-36to ~ 10-33 seconds

The Inflationary Epoch occurred during the Electroweak Epoch. It was caused by a phase transition from electronuclear plasma to electroweak plasma, phases that can no longer be generated today. During this period was a tremendous expansion of the universe, going from smaller than a proton to the size of a grapefruit. It was caused by a product of the phase transition known as the inflaton field a possessor of high energy, that, upon reaching its lowest possible energy state, released all its energy, fueling cosmic expansion. Quarks, anti-quarks, and gluons, biproducts of cosmic inflation, populated the early universe.

 

Quark Epoch - 10-12 to 10-6 seconds

During the Quark Epoch, temperatures were too high for quarks to bind, and quark-gluon plasma filled the universe. Eventually, the average energy of the universe dropped, slowing the particles in the plasma, and allowing quarks to bind. This triggered the Hadron Epoch.

Quark-Gluon Plasma - Image Declared Public Domain

 

Hadron Epoch - 10-6 to 1 second

During the Hadron Epoch, the mass of the universe was dominated by hadrons (mesons and baryons) and antihadrons. Soon, the temperature fell below the necessary temperature for pair production, and hadrons annihilated antihadrons, leaving a small amount of hadrons, and no antihadrons.

 

Lepton Epoch - 1 to 3 seconds

During the Lepton Epoch, the mass of the universe was dominated by leptons (electrons and neutrinos) and antileptons. Soon, the temperature fell below the necessary temperature for pair production, and leptons annihilated antileptons, leaving a small amount of leptons, and no antileptons.

 

Photon Epoch - 3 seconds to 380,000 years

During the Photon Epoch, photons, little packets of light energy, whizzed back and forth. However, we have no way of knowing what the universe looked like, because atoms are necessary to convey photons with information. This phase began with nucleosynthesis, a sub-epoch that lasted until 20 minutes after the Big Bang. Only light nuclei were produced, due to the decay of heavy nuclei without electrons to balance them out.

As the last epoch neared its end, temperatures dropped low enough for atoms to form, and a massive burst of light was produced, forming Cosmic Background Radiation, our best clue to life in the early universe.

 

Xavier Stone

 

Sources and Links

 

Giancoli, Douglas C. Physics. 6th ed. Upper Saddle River: Pearson Education Inc., 2005. 930-35.

http://en.wikipedia.org/wiki/Big_Rip

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

http://csep10.phys.utk.edu/astr162/lect/cosmology/planck.html

http://en.wikipedia.org/wiki/Planck_era

http://en.wikipedia.org/wiki/Symmetry_breaking

http://en.wikipedia.org/wiki/Grand_unification_epoch

http://en.wikipedia.org/wiki/Electroweak_epoch

http://www.lifesci.sussex.ac.uk/home/John_Gribbin/cosmo.htm

http://en.wikipedia.org/wiki/Inflationary_epoch

http://en.wikipedia.org/wiki/Quark_epoch

http://en.wikipedia.org/wiki/Hadron_epoch

http://en.wikipedia.org/wiki/Lepton_epoch

http://en.wikipedia.org/wiki/Photon_epoch

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