Many astronomers concur that a massive explosion of matter and energy created the cosmos. The Big Bang Theory, which is a model rather than a theory concerning the origin of the universe, is the name given to this hypothesis. Astronomers consider the concept to be the most plausible explanation for the universe's creation because recent data appear to support it. The Big Bang theory is predicated on the assumption that tiny pieces of matter have been slowly and steadily increasing, according to DeYoung and Whitcomb (1983, p. 1). This expansion resulted in the formation of stars, planets, and people.
The three major concepts of the model are the expansion of the universe, the presence of cosmic background radiation, and the presence of abundant helium and deuterium. The model tries to make an accurate, precise, and testable hypothesis in each of the three observations. The construction of the model has followed different stages with the latest one incorporating a detailed explanation of the universe and large scale structure (Uzan 2016 pg.1). However, the model fails to explain where the initial energy came from, what caused the explosion, and what causes it to expand. Nonetheless, new observations have allowed the model to further reconstruct its initial expansion details, making it radically different from the model astronomers had in mind at its conception. This paper looks at the three building concepts of the big bang theory and new observations that have made it consistent with scientific facts.
Key Concepts of Big Bang Theory
There are key concepts of the big bang theory that have made the model gain worldwide acceptance. These ideas are the expansion of the universe, the existence of cosmic background radiation, and the relative amount of deuterium and helium. These concepts present numerous facts about the nature of the universe. According to the theory, the expansion of the universe started at an unknown time in the past and at a high state of pressure and density (Alles, 2013 pg. 6). The universe was cooling down, and it grew bigger as different physical processes produced complex stars and galaxies (Rhee, 2013 pg. 38). Planck time is the name given to the earliest period that has significance in cosmology (Lemonick, 2004). This time, with an interval of 10 -43 of a second, can be used to describe the interplay between matter and radiation within space.
Scientific observations supporting Big Bang theory
Expansion of the universe
Evidence for the expansion of the universe has been supported by the redshift of light. As light travels from other galaxies to earth, the distance from the galaxy and the earth increases. This results in the wavelength of the light getting longer. Longer wavelengths of visible light are called redshift because they are red (Drayer, 2016). The redshift of light allows scientists to determine the speed of light and the direction of stars. This implies that stars are not just moving away from the earth, but also moving far away from each other (Gentry, 2004) pg. 4). One such scientist who was able to demonstrate that stars are moving far away from earth was Edwin Hubble, who managed to measure their distance (1977). According to Hubble's law, the further away one galaxy is from one another in space, the faster it appears to move. Objects observed in space have a Doppler Shift which can be interpreted as the relative velocity from the earth (Tiwari, 2004). The stars appear moving away from the earth, but given that all galaxies move away from each other, it looks like the earth is not moving. Galaxies also obey Hubble's law and therefore were once close together.
This leads to the conclusion that the universe is evolving; it was different in the past and will be different in the future. The question that should follow is what causes the galaxies to have different speeds and what causes the movement? Astronomers have made it clear that it is not the objects in space that are moving, but it is the fabric of space that is expanding. Using this information- Hubble's constant-, scientists have been able to estimate the age of the universe. This has been achieved by knowing the current distance and velocity of a given galaxy to tell how long it took to reach the distance from earth. Time is given by distance divided by velocity, which is equal to one divided by Hubble's constant for each galaxy. The answer becomes approximately 14 billion years for the age of the closest galaxy (Ball, 2003 pg. 3). The redshift presents the expansion factor that can be used to think about the expansion of the universe. The earth's surface receives light with a longer wavelength from the time it was emitted. The ratio of the two wavelengths is the amount of time the universe has expanded since the big bang theory and the time light traveled to earth (Rhee, 2013 pg. 6). If the universe has expanded by a factor of three, the wavelength will also have expanded by a factor of three.
Given that the universe has been expanding since the big bang, it is believed that the expansion factor has also been increasing. Also, the expansion of the universe will go on forever. It is argued that the Milky Way galaxy will merge with the nearby Andromeda galaxy in billions of years to come (Block et.al, 2006). The expansion factor equals the redshift plus one. If astronomers observe the galaxy at the redshift of one, then it can be argued that the universe has expanded by a factor of 2 since the light from one galaxy started traveling to earth. The moon is seen one second ago because that is the distance light takes to reach us from the moon. The sun is seen 8 minutes ago because it is the distance light takes to reach earth from the sun. The time light takes to travel from the nearest spiral galaxy, known as the Andromeda nebula, is 2 million years. This object can be seen with naked eyes at night, although the light people see from this galaxy is 2 million years old.
Cosmic background radiation
The discovery of cosmic background radiation added to the evidence of the big bang theory. Background radiation allows astronomers to see the universe during its initial stages of evolution and presents information about the origin of structures that resulted in galaxies. Since objects were much closer in the past than they are today, the density of the universe was higher in the past (Linde and Mezhlumian, 1994). The density of the universe is calculated by dividing the mass by the volume. By adding the mass in stars and the gas between galaxies, the density becomes 0.1 atoms per cubic meter (Rhee, 2013). Going by the redshift of five, which is the redshift distance of galaxies, the expansion factor reduces by a factor of six, and the volume will have shrunk by 200. Therefore, the density of the universe must have been 200 atoms per cubic meter at that time of the explosion.
According to Weinberg, in his book The First Three Minutes, the existence of background radiation could have been confirmed when the prediction was made (1977). If there was no background at the time of the explosion, the nuclear reaction would have happened so rapidly that a lot of the hydrogen present would have become heavier elements. This could not have taken place given that most of the matter in the universe is made of hydrogen. The only thing that could have stopped the rapid nuclear reaction from taking place was the intense radiation with extremely high temperatures and short wavelengths. This radiation would have successfully blasted apart nuclei that were forming fast. Cosmic radiation has survived since the explosion although its temperature has decreased as the universe continues to expand. Therefore, the current universe must be full of radiation but with an equivalent temperature which is less than its initial value.
The Abundances of Deuterium and Helium
The big bang theory explains why nearly 90% of atoms in the universe are hydrogen atoms. The model provides an accurate explanation for the abundance of lighter atoms such as deuterium, helium, and lithium. Astronomers have discovered that stars are made of atoms of the same kind as those of earth. In every 10 000 hydrogen atoms, there are 975 helium atoms, 6 oxygen atoms, and one carbon atom (Rhee, 2013 pg. 12). The sun makes energy by converting hydrogen into helium. However, the nuclear fusion in stars cannot be used to explain for all the helium in the universe. Creation of elements using hydrogen requires high temperatures that the sun cannot produce. For the nuclear fusion to occur, scientists argue that the process might have taken place in the first few minutes of the big bang explosion which produced the right amount of helium to match the ones seen in the stars. This is the same process that explains the abundance of lithium and deuterium. According to Robert (2006, pg. 343), Deuterium formed during the big bang theory and has since been destroyed in the stars. The conclusion is that it's only the lightest atoms that were created during the big bang and the heavier ones were made inside the stars.
As the explosion of matter during the big bang continued, the temperature reduced to 3_109 degrees Centigrade after about 14 seconds. The temperature at this point was low enough for electrons and positrons to be eliminated faster than they could be created (Robert, 2006). The energy released in the annihilation of electrons and positrons slow the cooling process although temperatures continue dropping to about 109 degrees Centigrade in three minutes. This temperature was sufficient enough for the formation of deuterium and helium. By the end of the three minutes, the universe was made of photons, neutrinos, a small amount of nuclear material, and a few electrons. The matter kept pulling apart as it increasingly cooled and became less dense. According to Alvarenga et al. (2001, pg. 5), after a few hundred years, it had cooled enough for electrons to merge with nuclei to make hydrogen and helium atoms. The gas produced, under the influence of gravity, condensed to create galaxies and stars.
Conclusion
The big bang theory is currently the most common explanation for the origin of the universe and the most consistent with modern scientific facts. New discoveries supporting the big bang theory claim that the universe expansion started at a finite time in a state of high density and pressure. The universe then started cooling and formed complex structures such as stars and galaxies. The redshift of light emitted from galaxies enabled cosmologists to estimate the age of the universe. By understanding the current distance and velocity of a particular galaxy- using Hubble's constant,-the age of the universe has been found to be approximately 14 billion years. Additionally, the presence of cosmic background radiation has made it possible to see the universe at its initial stages of creation.
This radiation must have existed to ensure nuclear fusion produced just the right amount of energy, and that hydrogen did not explode to form heavier elements. The big bang model also explains why there are lighter elements in the universe, such as hydrogen, helium, and delirium. Since the sun could not produce the right amount of energy needed for nuclear fusion, it has been argued that the big bang produced just the much-needed energy to produce helium seen in the stars. Although the theory fails to account for the origin of matter and energy that exploded, it has gone a long way to provide a detailed explanation for the expansion of the universe than any other theory. Hopefully, technological advancements and further discoveries in the future will help fill the cracks in Big Bang theory.
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