Cosmological Scale Of The Universe

When the average person hears the terms dark matter or dark energy, they probably do not truly appreciate the complexity and scope of the concepts involved. The terms dark matter and dark energy tend to obscure the high level of uncertainty that currently plagues researchers involved in these areas of study. However, before people can even begin to really understand these ideas, they must first acquire a basic understanding of the nature and scope of the universe, at least as much is possible for the human mind. The cosmological scale of the universe is so much larger than we as human beings can hope to comprehend in an intuitive manner.

To gain an appreciation of this scale, consider the following, the average human being is about 1.7 m

tall, slightly greater than 5.5 feet (Huang, 2010). The diameter of the Earth is about 12,700 km, or about 1.3x107 m (Huang, 2010). The diameter of Jupiter, into which about one thousand Earths could fit, is about 140,000 km, or about 1.4x108 m (Huang, 2010).

The diameter of our Sun, into which about one million Earths could fit, is about 1,400,000 km, or about 1.4x109 m (Huang, 2010). The largest star currently known to humans, VY Canis Majoris, has a diameter of about 3 billion kilometers, or about 3x1012 m (Huang, 2010). The Oort cloud of our solar system, the barrier of debris at the extreme limit of our Sun’s gravitational influence, is believed to have an outer diameter of about 1.5 trillion kilometers, or about 1.5x1015 m, this is also about 0.15 light years (Huang, 2010). The light year is a unit of measure based on how far light travels in one year, in a vacuum. The nearest star to our solar system, Proxima Centauri, is about 4.3 light years away, or about 4.5x1016 m (Huang, 2010). The Milky Way Galaxy, our home galaxy, is believed to have a diameter of about 120,000 light years, or 1.2x1021 m (Huang, 2010). The Local Galactic Supercluster of galaxies is believed to have a diameter of about 150,000,000 light years, or about 1.5x1024 m (Huang, 2010). The diameter of the observable universe is believed to be about 14 billion light years, actually

closer to 13.7, or about 1.4x1026 m (Huang, 2010). Basically, humans cannot see any light past this boundary because the light from the area beyond would not have had sufficient time to travel the requisite distance. Also, it is a reasonable conclusion that Earth is not in the exact center of the universe, so there is likely space beyond this boundary since current theory holds that the universe was created in a big bang that radiated out from a central point. Finally, an estimate, made in 2004, suggests that the actual universe is about 156 billion light years in diameter due to the effects of the expansion of space-time itself (Britt, 2004).
Given the immense scale of the universe, it becomes clear that humanity is but an infinitesimally small part within the cosmos. However, that does not prove that humanity is insignificant, it just casts doubt on the notion that the universe is a creation solely for the human species. The more humans come to understand about the universe, the more we are able to understand our role within it. This is one reason why the study of cosmology, i.e., the study of the nature and origin of the universe, is so important. It has risen out of a long process of scientific evolution that began with the questions humans had pertaining to existence. Namely, why are we here, and what is our purpose. Disciplines arose that addressed these questions, e.g., philosophy and religion. However, they were somewhat limited by the constraints of the time in which they arose, e.g., pressures from society coupled with a lack of technology and means of investigating nature.
Eventually, modern science arose and with it came more modern scientific disciplines such as chemistry, biology, physics, etc. Physics, the branch of science that investigates explanations and seeks an understanding of the nature of nature, matter and energy (Greene, 2004), gave rise to many branches, one of which is Cosmology. Cosmological studies help to address the fundamental questions humans have about nature through science. This process of scientific research also yields many unexpected benefits and discoveries that impact our world and improve the lives of its inhabitants. One does not have to look very far to see examples of this effect on society. An example that immediately comes to mind is the modern home computer. Today, a computer that fits on a desk, and is often much smaller, has more computing power than what was on the rocket that carried humans to the Moon. This is no small feat. Thus, it is abundantly clear that research into science, specifically cosmology, is beneficial to humanity and should be pursued.
To that effect, modern research in cosmology is focused on the latest set of mysteries, dark matter and energy. What are they? First, dark matter is matter that is not seen and is only indirectly detected through its gravitational effects on the motions of both stars in galaxies, and on galaxies in galactic clusters (Garfinkle & Garfinkle, 2008). Next, dark energy is a substance that has the characteristic of being gravitationally repulsive and is believed to be responsible for the accelerated expansion of the universe (Garfinkle & Garfinkle, 2008). In addition, consider that they both are believed to comprise the vast majority of the constituency of the universe. The specific numbers for the constituency of the universe tend to be slightly different depending on the source referenced. However, according to NASA, nearly 70% of the universe is made of dark energy, roughly 25% of dark matter, and the remaining 5% of all observable matter and energy (NAC Science Committee, n.d.). This alone is demonstrative of the great mystery surrounding the nature dark matter and energy.
Research into these areas is important for many reasons.

Consider the fact that there even is a rigorous debate about such concepts. This indicates that our current understanding of the nature of the universe is incorrect. Namely, our current explanations of physics on a cosmological scale, specifically pertaining to gravity, are somehow incomplete and/or lacking. A more complete understanding of these concepts will either expose erroneous concepts currently held as truth, or add to humanity’s current understanding of the nature of the cosmos, or both. Along the way, the scientific process of research and investigation will yield insights that will undoubtedly have unforeseeable influences on our society. Questions will likely be addressed in disciplines ranging from philosophy and religion, i.e., the nature of the origins of the universe and of existence, all the way to modern computing and optics technology, e.g., the new technologies being developed to make research into these areas of cosmology and astronomy possible that will likely benefit society at large through technological innovation and advancement.

For these reasons alone, it is clear that there is much to be gained from research into dark matter and energy. Further, an understanding of the nature of the universe from a cosmological perspective requires an in depth analysis of the collective nature of dark matter and dark energy. The following analysis will provide a look into the current research of these subjects

and will focus on what each possibly is, what the evidence is for the existence of each, current and future plans to measure both, and the cosmological implications of each.
On first glance, it becomes clear that there are many divergent viewpoints within the realm of research into dark matter and energy, certainly too many to be addressed in their entirety. However, there are arguments about each concept that are considered to be more in the mainstream than others. Thus, the leading arguments about dark matter and energy are an excellent place to begin. The most popular opinion about the nature of dark matter is that it is some kind of exotic particle that has yet to be discovered. Scientists can determine some boundaries for the nature of this particle based upon the effect that dark matter should have on the universe’s constituents, in order to adequately explain astronomical observations. A leading candidate for an exotic dark matter particle is something called a WIMP, or weakly interacting massive particle (Gates, 2009). One popular particle is thought to be a neutralino, another is something called an axion (Gates, 2009). For as little as scientists know about these particles, there is much that they can rule out. For instance, researchers have ruled out more conventional possibilities, such as: subatomic and atomic particles, and MACHOs (massive compact halo objects) (Gates, 2009). MACHOs are massive objects with large gravitational effects, but that are too dim for astronomers to see, e.g., black holes, neutron stars, gas clouds, white dwarfs, and low mass stars like brown dwarfs (Gates, 2009).