Although increasing advanced astronomy methods have yet to accurately determine the time and manner of the universe’s creation, observation of galaxies many billions of years old has enabled cosmologists to deconstruct the process, whose catalyst, designated the “Big Bang Theory,” occurred approximately 15 billion years ago.
The origin, not necessarily of the universe, but what can perhaps be more accurately designated the physical dimension, took place when a single, densely packed ball of matter, energy, and space reached unfathomable temperatures and cataclysmically exploded, covering an area the size of our solar system only minutes after its release. Before it condensed into subatomic particles, it manifested itself as a faint glow of radiation called the cosmic microwave background.
Collecting and cooling, this matter took its earliest form as primitive galaxies and stars, but continued to expand as a whole.
It is estimated that our own solar system was itself created five billion years ago, at which time the universe was two-thirds of its present size.
After millennia of cohesion, the universe itself consists of planets, dwarf planets, moons, satellites, asteroids, meteors, comets, and interplanetary medium, which itself is comprised of gas and dust.
The universe’s expansion has been determined by several noted astronomers. Employing photographic spectroscopy and examining several patches from the Lowell Observatory in Flagstaff, Arizona, Vesto Slipher, for example, measured light speed with spectral lines, while Edwin Hubble and his assistant, Milton Humason, concluded that the patches studied were actually galaxies. Because most of these spectra were of the longer, or redder, wavelengths, Slipher himself concluded, based upon the Doppler effect, that galaxies were receding from earth.
Employing a graph, in which the velocity of galaxy recession was plotted on the vertical axis and its distance on the horizontal one, Hubble determined that, the further the galaxy was from earth, the faster it was receding in all directions, indicating that the universe is both a continually expanding and accelerating one. The result, expressed as the Hubble Constant, states that velocity is proportional to distance. Although its numerical value has yet to be calculated, advanced tools and techniques, not the least of which is the Hubble Space Telescope itself, have placed that figure within the realm of reality.
Conceptualization of something as virtually infinite as the universe to a finite entity such as man with limited brain capacity is difficult, but the universe itself can be subdivided into the galaxies themselves, clusters of galaxies, and clusters of superclusters. Current estimates conclude that there are tens of billions of galaxies in the observable universe, of which Andromeda is visible with the naked eye from the northern hemisphere and two small satellite galaxies are observable from the southern hemisphere: the Large and Small Magellanic Clouds.
Analysis of the universe’s origin naturally leads to speculation of its termination, if any. Some believe that all galaxies will recede until they lose velocity, cease to move, and then fall back, until all matter once again collides into a single ball, thereby reversing the Big Bang dynamic. Alternatively designated the “oscillating theory of the universe” or the “Bang-Bang-Bang” theory, it would then entail a chain reaction of explosion, recession, and remission every ten billion years.