Tuesday, August 7, 2012

Big Bang Theory : The Evolution of Universe in Simple

The Big Bang theory tries to explain what happened at the very beginning of our universe and how it is being transformed in to current state by incorporating the findings of many individuals over the period of past several years. Before that moment there was nothing, and after that moment there was something called our universe.

Approximately 13.7 billion years ago, our universe was compressed into the confines of an atomic nucleus. Known as a singularity(God Particle?), this is the moment before creation when space and time did not exist.

Courtesy: Wiki Big Bang Illustration

After its initial appearance, it (God Particle?) 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, an expanding universe that began as an infinitesimal singularity. This is the Big Bang theory.

As the distance between galaxy clusters is increasing today, the theory states that everything was closer together in the past. There is little evidence regarding the absolute earliest instant of the expansion. Thus, the Big Bang theory cannot and does not provide any explanation for such an initial condition; rather, it describes and explains the general evolution of the universe going forward from that point on.

The Big Bang theory is a cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the Universe to cool and resulted in its present continuously expanding state. The Big Bang would have occurred approximately 13.75 billion years ago, which is considered the age of the Universe. According to the theory, after its initial expansion from a singularity, the Universe would have cooled sufficiently to allow energy to be converted into various subatomic particles, including protons, neutrons, and electrons. While protons and neutrons would have combined to form the first atomic nuclei only a few minutes after the Big Bang, it would then have taken thousands of years for electrons to combine with them and create electrically neutral atoms. The first element produced would then be hydrogen, along with traces of helium and lithium. Giant clouds of these primordial elements would then coalesce through gravity to form stars and galaxies, and the heavier elements would be synthesized either within stars or during supernovae.

Illustration is from The Birth of the Universe: The Kingfisher Young People’s Book of Space, 1998.
  Graphic drawn by Ed Gabel, former Associate Graphics Director of Time

Quantum theory suggests that moments after the explosion at 10 -43 second, elementary particles known as quarks begin to bond in trios, forming photons, positrons and neutrinos and were created along with their antiparticles.

Approximately 10−32 seconds into the expansion, a phase transition caused a cosmic inflation, during which the Universe grew exponentially. After inflation stopped, the Universe consisted of a quark–gluon plasma, as well as all other elementary particles. Temperatures were so high that the random motions of particles were at relativistic speeds, and particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions.

During this creation and annihilation of particles the universe was undergoing a rate of expansion many times. The universe doubled in size at least one hundred times in less than one thousandth of a second.

After one hundredth of a second, the electrons and protons started to combine and formed Helium. The neutrons combine with protons to form hydrogen and deuterium. These deuterium nuclei combine in pairs and formed helium nuclei.

Universe expansion: Artistic illustration. Courtesy to Wiki Big Bang illustration
The Universe continued to grow in size and fall in temperature, hence the typical energy of each particle was decreasing. After about 10−11 seconds, the particle energies drop to values that can be attained in particle physics experiments. At about 10−6 seconds, quarks and gluons combined to form protons and neutrons. A similar process happened at about 1 second for electrons and positrons.

After three minutes and one billion degrees temperature, neutrons and protons were slowing down enough in order to allow nucleosynthesis to take place. Atomic nuclei of helium was produced as two protons and neutrons each bonded.

The universe for the next 300,000 years began to expand and cool to a temperature of 10,000°K. These conditions allowed for helium nuclei to absorb free floating electrons and form helium atoms. Meanwhile hydrogen atoms were bonding together and forming lithium. This is the point where light can be perceived.

Over a period of time, the slightly denser regions of the uniformly distributed matter, gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars and galaxies .

Evidence for the Big Bang Theory

  • Reasonably certain that the universe had a beginning.
  • Galaxies appear to be moving away from us at speeds proportional to their distance. This is called "Hubble's Law,". This observation supports the expansion of the universe and suggests that the universe was once compacted.
  • 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.
  • The abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins.

Common Speculations

There are many speculations around the Big Bang theory. For example, People tend to imagine a giant explosion initially. At the same time experts say that there was no explosion; there was an expansion and still the universe continued to expand. Another misconception is that we tend to image the singularity as a little fireball appearing somewhere in space. According to the many experts, space didn't exist prior to the Big Bang.According to the British astrophysicists, Steven Hawking, George Ellis, and Roger Penrose, time and space had a finite beginning that corresponded to the origin of matter and energy. 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 or nothing.

Religious Impact

Big Bang theory cannot contradict the religious beliefs. Most of the religions, doctrine and emphasis that the universe is created by a super power say, the God. As long as Science cannot define what has caused the Big Bang to happen and what was the state before, the religious believes could continue to stay as such. Who created the initial nuclei? Who and how the Big Bang is initiated, the answer is probably that the God created the universe and initiated the Big Bang. !!!

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