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The Big Bang Theory: True or Not Essay

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Updated: May 18th, 2022


Humans usually prefer conviction and claim it from preachers, doctors and scientists. Many fields of knowledge have raised concerns for ages. One of the fields where humans are struggling to offer convicting answers to is the field of astronomy. This field has attempted to explain a number of concepts, but none of them has been given more prominence than the issue of the origin and age of the universe. This essay attempts to examine the fundamentals of astronomy regarding the age and origin of the modern universe. It will also shed light on the measurement of the age of the universe. Though astronomy may seem a purely science-oriented subject, a number of theories have been advanced to explain how the universe was created. For purposes of this essay, the theory that will be given priority is the Big Bang theory. The essay will also expound on the implication on recent findings concerning the age of the universe, as well as their implications on future telescopic activities.

Cosmology and the Big Bang Theory

The study of the universe from a scientific perspective about the large-scale properties that make up it is known as cosmology. The popular theory that attempts to explain the origin and evolution of the universe is the famous Big Bang theory. The Big Bang theory or model (as it will be frequently referred to in this essay) estimates the age of the universe to be 12 to 14 billion years. It posits that during that period, the portion of the universe that is visible today was only a few millimeters in size (Kutner, 2003 p. 21). Since then, it has stretched from its initial hot dense condition into the huge and much cooler cosmos currently inhabited by humans. Leftovers of the hot dense matter are seen as the modern very cold cosmic microwave background radiation, which is still found in the universe. These remnants are only visible to microwave detectors. They appear as a homogeneous glow across the entire sky.

Pillars of the Big Bang Model

The Big Bang model is based on two hypothetical pillars dating back to the early twentieth century. These pillars are General Relativity and Cosmological Principle. Albert Einstein developed the General Relativity pillar in 1916. One major postulation of the General Relativity concept is that gravity is no longer explained by a gravitational field but, instead, it should be a deformation of time and space itself. Physicist John Wheeler precisely posited that matter dictates space how to curve whereas space shows matter how to move (Freedman, 2002 p.13). One of the fundamental assumptions of the General Relativity principle is that matter in the universe is spread evenly on the largest scales.

Going by the above assumption, it is possible to calculate the equivalent gravitational impact of that matter. Given that gravity is a property of space-time according to the General Relativity principle, calculating this impact will be tantamount to calculating the dynamics of space-time itself (Porcellino, 2001 p.27). The second concept by which the Big Bang theory is based on is the Cosmological Principle. This principle postulates that matter in the universe is homogenous and isotropic when approximated over very large scales (Donald, 2001 p. 14). Just like the General Relativity principle, this principle is under constant tests to establish the actual distribution of galaxies.

The Homogeneity of the universe
Picture I: The Homogeneity of the universe

The above discussions point out that matter plays a very pivotal role in cosmology. This is because the average density of matter distinctively dictates the geometry of the universe. For instance, if the density of matter is less than the so-called critical density, the universe will be open and inestimable. However, if the density is greater than the critical density, the universe will be closed and predetermined. In a scenario whereby the density of the matter is equivalent to that of the critical density, the universe would be flat but infinite (Lineweaver, & Davis, 2005, p.12). It is crucial to note that the value of the critical density is very minute. This has prompted modern scientists to question the density of the matter in the universe. Though they have not yet arrived at a precise answer, there is an apparent consensus that this density is relatively close to the critical density.

The dynamics of the universe

The focus of this essay now shifts to the dynamics of the universe. To understand this, it is important to know the density (mass per unit volume) and pressure (force exerted per unit area) of the universe. Nevertheless, the general impression is that the universe began from a very small volume with an initial expansion rate (Andrei, 2004 p. 24). This event came to be dubbed as the Big Bang.

The rate of expansion of the universe has been decelerating since the Big Bang. This deceleration has been occasioned by the gravitational pull of the matter on itself (Freedman, 2002 p.7). This raises a key scientific question as to whether or not the destiny of the universe can be reversed by the gravitational pull if the force is adequately strong to cause a reverse of the expansion hence leading to a collapse of the universe back on itself (Alan & Paul, 2002 p.13). In deed, observations in the recent times have indicated a probability that the expansion of the universe may be accelerating. As such, chances are high that the evolution of the universe is now subject to a peculiar type of matter having a negative pressure (Freedman, 2002 p. 23). The picture below brings the concept of the expansion of the universe into perspective.

 The dynamics of the universe
Picture II: The dynamics of the universe

The picture above picture demonstrates several probable causes for the relative size of the universe against time. The green curve stands for a flat critical density whereby the expansion rate is constantly decelerating (NASA, 2011 p. 12). The blue curve indicates an open, low-density universe whereby the expansion is also decelerating but not like the critical density universe due to differences in the strength of the pull of gravity. The red curve demonstrates a universe whose larger portion of its mass or energy is prone to be in the very vacuum of space itself. This phenomenon is referred to as the cosmological constant. This phenomenon is responsible for dark energy, which causes acceleration of the expansion of the universe. Growing evidence indicates that the universe is following the red curve.

Limitations of the Big Bang Theory

One of the crucial points worthy noting is that the Big Bang did not occur at one point in space as an explosion per se. Instead, the phenomenon is perceived as the concurrent appearance of space everywhere in the universe. The other important point in this unfolding discussion is that, going by the definition of the universe, the term entails all of space and time, as it is presently known. In this case, it is beyond the scope of the Biog Bang theory to determine to what the universe is expanding. In addition, it is also outside the scope of the Big Bang model to pinpoint what gave birth to the Big Bang despite an existence of a myriad of tentative theories on the topic (Lineweaver, & Davis, 2005, p.9).

To add on the above disclaimers, the universe must have a finite age, which is approximately 13.7 billion years. As such, it is only possible to view a finite distance out into space equal to 13.7 billion light years. This is the famous horizon. Going by this argument, the Big Bang theory does not try to explain that region of space beyond the horizon. In addition, it is also possible that the universe has a more sophisticated global topology than that explained by the Big Bang theory while still possessing the same local curve.

Types of matter in the universe

As mentioned earlier in this essay, the geometry and evolution of the universe are dictated by fractional distribution of various types of matter. Given that both energy density and pressure contribute to the strength of gravity in General Relativity, cosmologists group types of matter considering the connection between the two. The central categorization leads to four types of matter namely radiation, baryonic matter, dark matter, and dark energy. Radiation consists of particles without or almost without mass moving at the pace of light. Some of the existing radiation matter includes photons and neutrons. This category of matter has a large positive pressure (Porcellino, 2001 p. 32).

Baryonic matter is the common matter, which comprises of protons, neutrons and electrons. This type of matter has, in essence, no pressure of cosmological significance. The third category of matter, dark matter, stands for the exotic or non-baryonic matter that intermingles with ordinary matter. Dark energy is a peculiar type of matter, or may be a feature of the vacuum itself, marked by a large negative pressure. In addition, this is the sole type of matter that may lead to the acceleration of the expansion of the universe. One of the biggest modern challenges of cosmology is to come up with the relative and total densities in each of the above types of matter because this is important to comprehend the evolution and the destiny of the universe.

Types of matter in the universe
Picture III: Types of matter in the universe

The current rate of expansion is usually articulated in terms of kilometers per second per Mega parsec or simply put, the Hubble Constant (Lineweaver, & Davis, 2003 p.21).

The Hubble Constant
Picture IV: The Hubble Constant

Measurement of the age of the universe: A brief history

The measurement of the speed by which the universe is expanding is dated back in the early 1920s when Edwin Hubble used a newly constructed 100-inch telescope to detect variable stars in a number of nebulae (Vogt, 2002 p. 6). He discovered that the variable stars had a certain pattern likened to that of a class of stars called Cepheid variables. Basing his argument on an earlier discovery, by Henrietta Levitt, connecting the period of a Cepheid variable to its luminosity, Hubble discovered that the nebula he had observed were not mere clouds within the earth’s Galaxy. Instead, they were external galaxies far outside the earth’s Galaxy (Peebles, Schramm, Turner & Kron, 2001(b), p.36).

It is believed that the Solar System is 4.5 billion years old while humans have been in existence for the last several million years (Peebles, Schramm, Turner & Kron, 2001 p.24). However, there seems to be an age crisis, astronomers approximate the age of the universe in two ways. The first is by measuring the age of the expansion of the universe and relating this to the Big Bang. The second means is by examining the oldest stars. The first means has been broadly discussed in the preceding section, As such; it is only fair if more attention is given to examining old stars (Schaff, 2001 p. 21).

Measurement of the universe by examining the oldest stars

Astronomers can put a lower boundary to the age of the universe by studying globular clusters. These are a dense collection of approximately a million stars. All the stars in a globular cluster formed at almost the same time. As such, they can function as cosmic clocks. For instance, a globular cluster that is more than twenty million years old will have all of its hydrogen burning stars will be smaller than that of ten solar masses (Kutner, 2003 p.41). This means that no single individual hydrogen-burning star will be more than a thousand times brighter than the sun. In a case where the globular cluster is more than a billion years old, there will be no hydrogen-burning star greater than two solar masses. Since the oldest globular clusters comprise of only stars smaller than 0.7 solar masses, they are dimmer than the sun. This implies that the oldest globular clusters are between eleven and eighteen billion years. Nevertheless, this approximation is not foolproof because there are uncertainties in the brightness of the stars or ignorance in the more details of stellar evolution.

Recent progress in astronomy

An earlier discussion in this attempted to show how astronomers use Cepheid variable as distance indicators. This endeavor has been faced by a number of challenges among them, difficulties in the determination of the distance to a nearby sample of Cepheid (Zeilik, 2002 p. 84). Luckily enough, recent technological advancements have made it possible for astronomers to use new detectors called change coupled devices or simply CCDS to fix these problems. Such evolutions have led to accurate study of the nearby galaxies. In addition, astronomers have come up with a number of new ways for determining relative distances tom galaxies (Schaff, 2001 p. 3


In conclusion, this essay is not a blue print for the determination of the modern age of the universe. Nevertheless, it has attempted to elaborate a number of concepts surrounding this hotly debated topic. In particular, the essay has taken a perspective of answering some of the frequently asked question in the field of astronomy and in particular, the age of the universe. Though many hypotheses explain this phenomenon, prominence has been given to the Big Bang theory, its limitations. The method of determining the age of the universe through a close, examination of the oldest stars has also been discussed. Lastly, the recent developments in the field of astronomy and their implications on the future of the field have been highlighted.


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