Evidence For The Big Bang Essay, Research Paper
Evidence for the Big Bang Theory:
Whether you happen to be walking down a neighborhood street on a starry night, or trekking across Canada in a car, or rising to the bright sunshine that beams through your bedroom window in the morning, many of us easily take it for granted, or perhaps it simply goes unnoticed that we are, human beings living on a planet called Earth; or that the beautiful stars in the sky have existed long before we did; or that our planet is but a tiny speck of sand in the grand Universe. Where did it all come from? many people before us have asked themselves. Scientists of Cosmology, who study large scale structures and the origin of the universe, have struggled with this very question and have developed several theories to answer just that. One such theory is called the Big Bang. It has become one of the most widely accepted theories of our time because in several ways, it provides tangible evidence to explain the origin of the universe. The Big Bang Theory assumes that the Universe began as cosmic singularity as small as an atomic nucleus which is infinitely small and infinitely curved and that all matter and energy were concentrated in a single point (Impey & Hartman, 513). This implies that the universe as an evolving model that existed in space-time, which began from an initial singularity and subsequently expanded (I&H, 513). Fundamentally, this theory tries to account for the physical events that took place in the very first moments during the creation of the universe, well over 15 million years ago. In much of the literature, it is evident that the three key pieces of evidence that support this theory include: the presence of cosmic microwave background radiation, galaxies are taking part in a universal expansion, as indicated by the linear relationship between distance and redshift, and the discovery of light elements (nucleosynthesis) in the universe s atmosphere that indicate the plausible event of a Big Bang (I&H, 513). Despite the contentions some scientists have with this theory for its inability to explain other phenomena, it remains today one of the most compelling theories used to explain how the universe came into being (http://liftoff.msfc.nasa.gov/academy /universe/b_bang.html).
In 1915, Albert Einstein developed his Theory of Relativity, which attempted to make his equations of relativity mesh with the incorrect belief that the universe was stable and static, with no beginning nor an end (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html ). To recall, his Theory of
Relativity identified the relativity of gravity with that of the curvature of space-time, and from this theory, he yielded a static model of the universe. His failing however, was his account that the universe was static and unchanging, which was later challenged by meteorologist Alexander Friedmann, and mathematician Georges Lemaitre both of whom, without concrete observational evidence for universal expansion, individually discovered the solutions to Einstein s equations of gravitation which described an indefinitely expanding universe (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html).
The first of the key pieces of evidence of the Big Bang, according to The Universe Revealed, is the existence of cosmic microwave background radiation. It is a diffuse isotropic radiation whose spectrum is that of a blackbody at 3 degrees Kelvin and is most intense in the microwave region of the spectrum (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html ). Consequently, this cold, uniformly intense radiation can only be detected by radio telescopes. It is postulated that this radiation came from the cooled residue of the initial explosion from which the universe evolved (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html ). What is interesting is that the scientist, George Gamow postulated the existence of this radiation even before the radio telescopes capable of detecting the microwave radiation were even created. Upon its discovery, scientists noticed its high degree of uniformity which proved its origin was from the farthest points of the universe, since any radiation produced near the sun, in our galaxy or nearby galaxies would be unevenly distributed (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html). Furthermore, the cold temperature of 3 degrees Kelvin accounts for the notion that the universe was (and is) continually expanding, in that if the blackbody radiation was traced in time, it becomes hotter until it reaches the conditions to create blackbody radiation; a state of perfect equilibrium between radiation and matter (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html). Quite remarkably, this background cosmic microwave radiation is tangible evidence of a cataclysmic event that occurred long ago.
The second major piece of evidence that supports the Big Bang Theory is the relationship between a galaxy s redshift and its distance, which was demonstrated by Edwin Hubble in 1929. Edwin Hubble was greatly influenced by the work of an astronomer, William de Sitter, who hypothesized in 1917 that “the universe possessed the peculiar property that the light from the most distant regions became progressively reddened as the distance increased” (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html). Following this logic,
Hubble’s redshift is due to a Doppler shift of light from a galaxy that is receding, and provides a credible explanation for Hubble’s law that states, the distance of the galaxies from us is linearly proportional to their redshift and therefore is linearly proportional to their relative velocity of recession. (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html).
In essence, galaxies that are twice as far from us than another move twice as fast. This indicates that it has taken every galaxy the same amount of time to move from a common point of origin to its current position, despite where that point is (Lecture, April 4, 2001).
The last key piece of evidence for the Big Bang is the presence of a large number of light elements found throughout the universe’s atmosphere. The theory predicts that light elements were fused together in the first few moments of the initial explosion (nucleosynthesis), which was made conducive by the very high temperatures that were believed to have existed during these first minutes. Deuterium, for example, is an ‘extremely fragile element,’ which consists of helium and 1 isotope of hydrogen. It is known that this element is destroyed in stars because it cannot survive the high temperatures at the center of star formation, but it is not produced, so therefore, it can only exist in interstellar matter that has not yet formed into stars (I&H, 518). Other elements that have been found in abundance in the universe include hydrogen, helium, and lithium. Hydrogen’s relation to helium remains quite consistent from galaxy to galaxy, which demonstrates its cosmological origin (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html). Lithium found in the oldest stars is much greater than that found in younger ones which indicates that this light element was created long ago during the ‘Big Bang.’ This shows that lithium has very early and pre-galactic origins (http://www.bowdoin.edu/dept/physics/astro.1997/astro4/bigbang.html).
This following figure was taken from The Universe Revealed, which demonstrates the predicted abundance of light elements from nucleosynthesis calculations (solid curves) compared with observational bounds in the abundances (light horizontal bars). There is a relatively narrow range of density (dark vertical bar) for which the observation of all four elements agrees with the model (I&H, 518).
In summary, there is a wealth of tangible evidence to demonstrate with a high degree of certainty that the Big Bang Theory is a convincing and plausible explanation with regards to the creation of the Universe. The discovery of cosmic microwave background radiation, Hubble’s demonstrable relationship between a galaxy’s redshift and its distance, and the abundance of light elements in the universe’s atmosphere lend firm, supporting evidence to the Big Bang Theory which aims to explain the events and processes that occurred to create our universe into what we know it today. What is most intriguing is that many of these discoveries were postulated even prior to the availability of technologies capable of detecting their existence in the universe’s atmosphere. However, in spite of the few outstanding questions the Big Bang Theory fails to answer, there are several proofs that guide our impetus to entrust in its validity.
Works Cited :
Impey and Hartman. The Universe Revealed. (Brooks/Cole). 2000. pg 513-518.
Professor Kaspi. Lecture: 198-204B Planets, Stars and Galaxies. McGill University, April 2001.