One of the most persistently asked questions has been: How was the universe created? Many once believed that the universe had no beginning or end and was truly infinite. Through the inception of the Big Bang theory, however,no longer could the universe be considered infinite. The universe was forced to take on the properties of a finite phenomenon, possessing a history and a beginning.
About 15 billion years ago a tremendous explosion started the expansion of the universe. This explosion is known as the Big Bang. At the point of this event all of the matter and energy of space was contained at one point. What existed prior to this event is completely unknown and is a matter of pure speculation. This occurrence was not a conventional explosion but rather an event filling all of space with all of the particles of the embryonic universe rushing away from each other. The Big Bang actually consisted of an explosion of space within itself unlike an explosion of a bomb were fragments are thrown outward. The galaxies were not all clumped together, but rather the Big Bang lay the foundations for the universe.
The origin of the Big Bang theory can be credited to Edwin Hubble. Hubble made the observation that the universe is continuously expanding. He discovered that a galaxys velocity is proportional to its distance. Galaxies that are twice as far from us move twice as fast. Another consequence is that the universe is expanding in every direction. This observation means that it has taken every galaxy the same amount of time to move from a common starting position to its current position. Just as the Big Bang provided for the foundation of the universe, Hubbles observations provided for the foundation of the Big Bang theory.
Since the Big Bang, the universe has been continuously expanding and, thus, there has been more and more distance between clusters of galaxies. This phenomenon of galaxies moving farther away from each other is known as the red shift. As light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to wavelengths being stretched.
In addition to the understanding of the velocity of galaxies emanating from a single point, there is further evidence for the Big Bang. In 1964, two astronomers, Arno Penzias and Robert Wilson, in an attempt to detect microwaves from outer space, inadvertently discovered a noise of extraterrestrial origin. The noise did not seem to emanate from one location but instead, it came from all directions at once. It became obvious that what they heard was radiation from the farthest reaches of the universe which had been left over from the Big Bang. This discovery of the radioactive aftermath of the initial explosion lent much credence to the Big Bang theory.
Even more recently, NASAs COBE satellite was able to detect cosmic microwaves eminating from the outer reaches of the universe. These microwaves were remarkably uniform which illustrated the homogenity of the early stages of the universe. However, the satellite also discovered that as the universe began to cool and was still expanding, small fluctuations began to exist due to temperature differences. These fluctuations verified prior calculations of the possible cooling and development of the universe just fractions of a second after its creation. These fluctuations in the universe provided a more detailed description of the first moments after the Big Bang. They also helped to tell the story of the formation of galaxies which will be discussed in the next chapter.
The Big Bang theory provides a viable solution to one of the most pressing questions of all time. It is important to understand, however, that the theory itself is constantly being revised. As more observations are made and more research conducted, the Big Bang theory becomes more complete and our knowledge of the origins of the universe more substantial.
THE FIRST ATOMS
Now that an attempt has been made to grapple with the theory of the Big Bang, the next logical question to ask would be what happened afterward? In the minuscule fractions of the first second after creation what was once a complete vacuum began to evolve into what we now know as the universe. In the very beginning there was nothing except for a plasma soup. What is known of these brief moments in time, at the start of our study of cosmology, is largely conjectural. However, science has devised some sketch of what probably happened, based on what is known about the universe today.
Immediately after the Big Bang, as one might imagine, the universe was tremendously hot as a result of particles of both matter and antimatter rushing apart in all directions. As it began to cool, at around 10^-43 seconds after creation, there existed an almost equal yet asymmetrical amount of matter and antimatter. As these two materials are created together, they collide and destroy one another creating pure energy. Fortunately for us, there was an asymmetry in favor of matter. As a direct result of an excess of about one part per billion, the universe was able to mature in a way favorable for matter to persist. As the universe first began to expand, this discrepancy grew larger. The particles which began to dominate were those of matter. They were created and they decayed without the accompaniment of an equal creation or decay of an antiparticle.
As the universe expanded further, and thus cooled, common particles began to form. These particles are called baryons and include photons, neutrinos, electrons and quarks would become the building blocks of matter and life as we know it. During the baryon genesis period there were no recognizable heavy particles such as protons or neutrons because of the still intense heat. At this moment, there was only a quark soup. As the universe began to cool and expand even more, we begin to understand more clearly what exactly happened.
After the universe had cooled to about 3000 billion degrees Kelvin, a radical transition began which has been likened to the phase transition of water turning to ice. Composite particles such as protons and neutrons, called hadrons, became the common state of matter after this transition. Still, no matter more complex could form at these temperatures. Although lighter particles, called leptons, also existed, they were prohibited from reacting with the hadrons to form more complex states of matter. These leptons, which include electrons, neutrinos and photons, would soon be able to join their hadron kin in a union that would define present-day common matter.
After about one to three minutes had passed since the creation of the universe, protons and neutrons began to react with each other to form deuterium, an isotope of hydrogen. Deuterium, or heavy hydrogen, soon collected another neutron to form tritium. Rapidly following this reaction was the addition of another proton which produced a helium nucleus. Scientists believe that there was one helium nucleus for every ten protons within the first three minutes of the universe. After further cooling, these excess protons would be able to capture an electron to create common hydrogen. Consequently, the universe today is observed to contain one helium atom for every ten or eleven atoms of hydrogen.
While it is true that much of this information is speculative, as the universe ages we are able to become increasingly confident in our knowledge of its history. By studying the way in which the universe exists today it is possible to learn a great deal about its past. Much effort has gone into understanding the formation and number of baryons present today. Through finding answers to these modern questions, it is possible to trace their role in the universe back to the Big Bang. Subsequently, by studying the formation of simple atoms in the laboratory we can make some educated guesses as to how they formed originally. Only through further research and discovery will it be possible to completely understand the creation of the universe and its first atomic structures, however, maybe we will never know for sure.
AGE OF THE UNIVERSE
We now have something of a handle on two of the most important quandaries concerning the universe; however, one major question remains. If the universe is indeed finite, how long has it been in existence? Again, science has been able to expand upon what it knows about the universe today and extrapolate a theory as to its age. By applying the common physical equation of distance over velocity equaling time, which again uses Hubbles observations, a fairly accurate approximation can be made.
The two primary measurements needed are the distance of a galaxy moving away from us and that galaxys red shift. An unsuccessful first attempt was made to find these distances through trigonometry. Scientists were able to calculate the diameter of the Earths orbit around the sun which was augmented through the calculation of the Suns motion through our own galaxy. Unfortunately, this calculation could not be used alone to determine the enormous distance between our galaxy and those which would enable us to estimate the age of the universe because of the significant errors involved.
The next step was an understanding of the pulsation of stars. It had been observed that stars of the same luminosity blinked at the same rate, much like a lighthouse could work where all lighthouses with 150,000 watt light bulbs would rotate every thirty seconds and those with 250,000 watt light bulbs would rotate every minute. With this knowledge, scientists assumed that stars in our galaxy that blinked at the same rate as stars in distant galaxies must have the same intensity. Using trigonometry, they were able to calculate the distance to the star in our galaxy. Therefore, the distance of the distant star could be calculated by studying the difference in their intensities much like determining the distance of two cars in the night. Assuming the two cars headights had the same intensity, it would be possible to infer that the car whose headlights appeared dimmer was farther away from the observer than the other car whose headlights would seem brighter. Again, this theory could not be used alone to calculate distance of the most far-away galaxies. After a certain distance it becomes impossible to distinguish individual stars from the galaxies in which they exist. Because of the large red shifts in these galaxies a method had to be devised to find distance using entire galaxy clusters rather than stars alone.
By studying the sizes of galaxy cluster that are near to us, scientists can gain an idea of what the sizes of other clusters might be. Consequently, a prediction can be made about their distance from the Milky Way much in the same way the distance of stars was learned. Though a calculation involving the supposed distance of the far-off cluster and its red shift, a final estimation can be made as to how long the galaxy has been moving away from us. In turn, this number can be used inversely to turn back the clock to a point when the two galaxies were in the same place at the same time, or, the moment of the Big Bang. The equation generally used to show the age of the universe is shown here:
(distance of a particular galaxy) / (that galaxys velocity) = (time)
4.6 x 10^26 cm / 1 x 10^9 cm/sec = 4.6 x 10^17 sec
This equation, equaling 4.6 x 10^17 seconds, comes out to be approximately fifteen billion years. This calculation is almost exactly the same for every galaxy that can be studied. However, because of the uncertainties of the measurements produced by these equations, only a rough estimate of the true age of the universe can be fashioned. While finding the age of the universe is a complicated process, the achievement of this knowledge represents a critical step in our understanding.
In summary, we have made a first attempt at explaining the answers that science has revealed about our universe. Our understanding of the Big Bang, the first atoms and the age of the universe is obviously incomplete. As time wears on, more discoveries are made, leading to infinite questions which require yet more answers. Unsatisfied with our base of knowledge research is being conducted around the world at this very moment to further our minimal understanding of the unimaginably complex universe.
Since its conception, the theory of the Big Bang has been constantly challenged. These challenges have led those who believe in the theory to search for more concrete evidence which would prove them correct. From the point at which this chapter leaves off, many have tried to go further and several discoveries have been made that paint a more complete picture of the creation of the universe.
Recently, NASA has made some astounding discoveries which lend themselves to the proof of the Big Bang theory. Most importantly, astronomers using the Astro-2 observatory were able to confirm one of the requirements for the foundation of the universe through the Big Bang. In June, 1995, scientists were able to detect primordial helium, such as deuterium, in the far reaches of the universe. These findings are consistent with an important aspect of the Big Bang theory that a mixture of hydrogen and helium was created at the beginning of the universe.
In addition, the Hubble telescope, named after the father of Big Bang theory, has provided certain clues as to what elements were present following creation. Astronomers using Hubble have found the element boron in extremely ancient stars. They postulate that its presence could be either a remnant of energetic events at the birth of galaxies or it could indicate that boron is even older, dating back to the Big Bang itself. If the latter is true, scientists will be forced once again to modify their theory for the birth of the universe and events immediately afterward because, according to the present theory, such a heavy and complex atom could not have existed.
In this manner we can see that the research will never be truly complete. Our hunger for knowledge will never be satiated. So to answer the question, what now, is an impossibility. The path we take from here will only be determined by our own discoveries and questions. We are engaged in a never-ending cycle of questions and answers where one will inevitably lead to the other.
COBE continues to search the outer reaches of the universe
It is extremely difficult to separate this subject of science from daily existential pondering. Everyone at some point in time has grappled with the question of why we are here? Some have found refuge in the sheer philosophic nature of this question while others have taken a more scientific approach. These particular wanderers have taken the question to a higher level, concentrating not only on human existence but the existence of everything we know as real.
If you sit and try to imagine the whole of the entire universe it would be mind-boggling. However, science has now told us that the universe is, in fact, finite, with a beginning, a middle, and a future. It is easy to get caught up in the large scale of the issue in discussing years by the billions, yet, this time still passes. As we travel through our own lives here on Earth, we also travel through the life of our universe.
In this chapter, we have made some attempts to explain this journey. It is odd that we will never truly know how it began. We can only speculate and give our best guess. Through our own devices we have been able to produce evidence that these guesses are close to the truth. But centuries from now, will the human race compare us to those who once thought of the Earth as the center of the universe?
Baryons– common particles including photons and neutrinos created at approximately 10^-33 seconds after the Big Bang
Deuterium– a heavy isotope of hyrogen containing on proton and one neutron
Hadrons– composite particles such as protons and neutrons forming after the temperature drops to 300 MeV
Leptons– light particles existing with hadros including electrons, neutrinos and photons
Red Shift– shift toward the red in the spectra of light reaching us from the stars in distant galaxies
Tritium– transitional element between deuterium and the formation of a helium nucleus