| The standard model of the Big Bang theory takes three possibilities into consideration. The first one is the open Friedmann-Lemaitre theory on the universe in which hyperbolically curved space is destined to expand forever. The second theory is the closed Friedmann-Lemaitre theory on the universe in which spherically curved space is destined to collapse again. The third one is the Einstein-de-Sitter theory that calculates that the flat space of the universe is destined to continually expand as well. Although these three models do not differ greatly in the initial and beginning fazes of the evolution of the universe, they do differ in their later phases and as one can see, they predict very different futures for our universe. One of the most interesting thoughts that arise out of this framework is that the universe was not always in the state that we see it in currently. To examine how the universe evolved, we must trace back through the expansion of the universe, coming as close as possible to the exact moment of the Big Bang. Probably the most astounding fact is that we are now in a position to describe the universe as it existed during most of the first second of existence. (Trefil 20) In its early stages, according the Big Bang theory, the universe was in thermal equilibrium. A searing light pervaded all locations and traveled in every direction, with the characteristics and qualities of a blackbody at exceedingly high temperatures. Early on in creation, the temperature was in the trillions of degrees because it was in a highly compressed, primordial state. At this extremely early stage of creation, particles of opposite charge freely moved around independently of one another, in a state of matter called plasma (Trefil 23). As the space expanded from a single point of origin, the wavelengths of light stretched out as well. Likewise, the expansion of the space stretched the wavelengths shifting the extremely high temperature blackbody spectrum to that of a lower temperature. Blue light shifted to the cooler red light region, and the universe cooled. As the universe cooled, certain forms of nuclei, definite amounts of helium, hydrogen, and lithium were formed, as well as other forms of elementary particles. About 1,000,000 years later, and almost 15 billion years ago, the universe became cool enough for atoms to finally form. Soon after the formation of atoms and the subsequent attraction of particles of opposite charges, another natural process began (Trefil 45). Under the expanding, new materials began to come together in clumps. As the universe expanded, matter was being brought together in these clumps by the force of attraction in gravity. Within each clump, the gravitational forces continued to operate, drawing large clouds of gases together to form nebulae. Eventually, the clumps and clouds of gas would form stars through a process known as fusion. A gas cloud had little choice but to collapse and fragment into what we now know as stars. The random motion of its atoms provides a pressure that can resist gravity for only a very short time, with atoms colliding, radiating because of the presence of heavy atoms such as carbon, losing their kinetic energy of motion, and eventually causing a cool down and a collapse. As the gas clouds collapsed into little clumps; these clumps merged together into larger, mixed fragments, and grew by accreting gas from their surroundings (Silk, Cosmic Enigmas 65). This collapsing gas soon became sufficiently dense to begin radiating energy from atomic collisions, and thus the first stars were born. |
| Over time many of the star clusters dissolved because of disruptive gravitational forces exerted by other clouds, and a galaxy emerged which resembled the Milky Way (Silk, Cosmic Enigmas 69). The most prominent feature of this early galaxy was a rotating disk of stars and gas clouds, along with a compact central spheroid shape of stars that developed from those collapsing gas clouds. Five billion more years would go by before one of these interstellar clouds would birth our solar system, condensed from the remnants of earlier stars. Finally, simply put, chemical processes would occur to link atoms, which were billions of years in the making from the origin of the universe, together to form molecules, and then eventually complicated solids and liquids, and finally bringing us to where humans stand now. With our ability to observe new wavelengths of light besides the optical region, we have discovered much evidence that supports the Big Bang theory. Probably the most persuasive evidence for this theory is the presence of cosmic microwave background radiation, which can only be detected by radio telescopes. Cosmic microwave background radiation is diffuse isotropic radiation whose spectrum is that of a blackbody at 3 degrees Kelvin and consequently is most intense in the microwave region of the spectrum (Silk, Big Bang 1989 456). This radiation is thought to come from the cooled residue of the initial explosion from which the universe evolved. Because microwaves are of shorter wavelengths, only several centimeters wide, and are thus not in the optical window, we are not able to directly observe these. Microwave radiation also does not usually produce heat, except at extremely high intensity, making it difficult to detec |