The Big Bang: Proof that the Universe is Expanding
Rahul's Essays
The Big Bang: Proof that the Universe is Expanding
By Rahul Gladwin
July, 2000.
From the earliest times, humans have gazed into the heavens and pondered the mystical lights they saw there. The ancients merely observed the movements in the universe in order to predict the coming of floods or the time to offer sacrifices to the gods. The old universe was built on the basis of philosophical and religious thought. Today, after thousands of years, the various breakthroughs in science and technology have enabled us to study and measure the universe extensively and with great precision. Modern technology has pushed us to our maximum limits; we not only care about what the universe looks like today, but what it looked like at the dawn of time . The early 20th century saw some rather bizarre theories about the formation of the universe. Although these theories differ from each other in many ways, they have scientific proof that the universe is not static; the universe is expanding.
The old universe conceived by the our ancestors was small, static and earth-centred, and it was full of spirits and mystical creatures (Guth 71). With the passage of time, humans became more intelligent and their thoughts became more complex. The cavemen living at Lascaux caves, thousands of years ago, named the sun the "Sun Spirit" and the moon the "Moon Spirit" (Bergmann 22). They observed their surroundings and made reasons about them. They created religion by reasoning that there were supreme beings that controlled the universe. Before writing was invented, the ancients had named the celestial bodies (Watson 301). Before ethical values were recognized, they bowed before the sun and the moon. Before the sand-glass or the water-clock were invented, humans followed the heavenly motions, numbering the days, months, seasons and years. To the ancient travellers and navigators, the stars in the sky were signposts that told them the directions (Weizacker 20). To the farmer, the heavens foretold the times of planting and the coming of rain. It was as if God had created the heavens in order to guide the early humans before they became intelligent enough to guide themselves. To the ancient Egyptians, the universe was the body of the goddess Nut (Bergmann 6). Under Nut lay the body of Geb, god of earth. The goddess Nut was supported by the Shu, god of wind. Geb, the god of earth lay on the ground and supported Shu. The sun travelled through Shu.
The study of Astronomy as we know it developed when humans began to study the movements of the celestial bodies in greater detail. Ptolemy, a Greco-Egyptian astronomer systematized a theory: The Universe was revolving around the stationary fixed Earth at its centre (Watson 6). This doctrine was accepted by the Church and remained unchallenged throughout the Middle Ages. After 1500 years of existence, however, the theory was disproved by a Polish astronomer Nicholas Copernicus who revolutionized the worlds of science, religion and culture. Copernicus claimed that the sun was the centre of the solar system (Watson 11). However, he faced such fierce opposition from the Church that he had to withdraw his theory. Galileo, about a hundred years later, again brought up the subject, but was placed under house arrest (Watson 13).
However, by the next generation, Church opposition to a sun-centred universe was waning. Brilliant astronomers like Brahe and Kepler were studying the heavens and came up with concepts and ideas the old world had never heard of. Kepler's laws were the foundation for Newton's Laws of Gravitation (Eddington 63). Using this law, Newton was able to explain many scientific concepts like the trajectories of cannon balls and the tides, and also predict solar and lunar ellipse in greater detail than was ever possible before. Using Newton's laws, astronomers predicted and later discovered the existence of the planets Neptune and Pluto. Even though Newton's equations were the most important work in science, they began to be questioned by scientists (Watson 332). The astronomers' doubt had to do with the propagation of electromagnetic radiation through the stationary space Newton had conceived.
Furthermore, sixteen year old Albert Einstein came up with the General Theory of Relativity in the early 1900's that shook the scientific world (Resnic 60). Einstein said that space and matter are interdependent. To come to this conclusion, Einstein developed an extensive system of equations that gave a comprehensive explanation of the universe from black holes to neutron stars (Watson 332). In fact, using his equations, Einstein had developed a nearly perfect theoretical model of the universe and amazingly, many of his predictions were tested and confirmed by scientists. For example, Einstein's famous theory about mass bending space was tested and confirmed during a total solar eclipse. Einstein himself, however, was not totally satisfied and believed that some his equations had a flaw because some of his results were totally inexplicable (Guth 27). He had discovered that for his equations to be held true, the universe must be either expanding or contracting. This was the first theoretical proof that the universe was not static (Taylor 47). This was completely absurd because it was never thought that the universe was dynamic. Therefore, he fudged a "cosmological constant" into his equations to make the Universe static; however, Einstein was too late. Alexander Friedmann, a Russian mathematician and meteorologist had already studied Einstein's equations and discovered that the universe was dynamic and that new the "cosmological constant" was a flaw (Resnic 63). A similar discovery was made by a Belgian priest Henri Lemaitre. The only thing that was left to do was to test and prove the theory of universal expansion on the basis of solid observational data.
Further study of universal expansion was based on a concept called "red-shift". The concept had been speculated by the scientist Christian Doppler in 1842 (Gribbin 28). Doppler studied sound waves and discovered that when a sound emitting object was approaching us, its sound had a different frequency than when it was receding from us. The sound waves of an approaching object were at a higher frequency and shorter wavelengths, and each successive wave crest was observed by the observer a little earlier (Coleman 74). The sound waves of a receding object were at a lower frequency and higher wavelengths, and each successive wave crest was observed a little later. The changing of frequency in sound waves was called "Doppler Effect" in his honor. Doppler also theorized that these rules followed by sound waves may also be obeyed by light waves. In 1848, a French physicist had already shown that an object approaching us emitted a bluish light, and an object receding from us emitted a reddish light (Carnap 52). This is because blue light has a shorter wavelength and red light has a longer wavelength. Movement in space was observed as early as 1868, but it was not taken seriously at that time. Spectrum analysis was introduced by the chemist Sir William Huggins, who attached a prism to his reflecting telescope and discovered that the light of the star Sirius had moved slightly towards the red part of the spectrum (Born 61). The star was moving away from the earth at a speed of 26-36 mile/sec. In the 1920's, many astronomers, including Edwin Powell Hubble, were busy cataloguing galaxies and their distances from earth (Gribbin 52). As they worked they made the most bizarre discovery in the history of astronomy: the further away the galaxy, the more shifted its light was towards the red part of the spectrum; the galaxies appeared redder: they were moving away from the earth. This meant that the universe was expanding, but the astronomers needed more scientific proof to come to that conclusion.
Moreover, in 1929, Edwin Hubble with partner Milton Humason observed and studied hundreds of galaxies from the 100-inch telescope on Mount Wilson (Eddington 28). They found out that only about 20% of the galaxies were stationary or were approaching us, the rest were indeed fleeing away from us in all directions with tremendous speeds (Cupra 37). Hubble graphed the velocity of the galaxy versus its distance and found a straight-line relationship: V = Ho x D, where Ho is the Hubble's constant, V = the velocity and D = the distance. This relationship was called the Hubble's Law and it stated that the speed with which a galaxy recedes from us is directly proportional from its distance from us (Resnic 60). From looking at the graph, Hubble speculated that at some point back in time, the velocities of all the galaxies must have been zero. This thought provoked the development of the famous Big Bang theory of universal expansion (Bergmann 24). The theory states that the universe evolved from an extremely hot, dense and small lump of matter that exploded about 15 billion years and created space and matter as we see in today (Bergmann 26). Although the Big Bang theory set forth more important proofs about universal expansion than any other theory, scientists were still not completely satisfied. One of the most important speculations of the Big Bang theory was the constant emission of microwave background radiation from the universe (Weizascker 45). In 1940, George Gamov and his co-workers guessed that if the universe started with the Big Bang, the early universe must have been filled with intense radiation, which implies: the earlier we go back in time, the more dense was the radiation (Wolf 293). In the present time, this radiation would be the cooled left over residue of the explosion and should still be detected today. If detected, this radiation would be the most convincing proof of universal expansion.
Even though the supporters of the Big Bang model tried hard to detect such radiation from outer space, they couldn't because they did not have the technical capability to do it. Radio astronomers simply said that the radiation was undetectable (Guth 66). The idea of such radiation was completely forgotten until 1963 when it was unexpectedly discovered by two engineers who were trying to locate the source of static in an experimental radio receiver. Arno Penzias and Robert Wilson from Bell Laboratories designed and built an antenna in order to study electromagnetic radiation (Wolf 297). The antenna, to be used for satellite communications, stood on top of Crowford Hill. It had a diameter of twenty feet and looked like a familiar radio dish. The system was designed in such a way that it collected microwaves from the sky, concentrated them at a point and transmitted the radiation into a small cabin at the bottom of the dish (Weyl 30). The two engineers found out that they received a constant background radio noise independent of the direction in which they pointed their antenna. They checked and re-checked all the connections and tried again. The process also included carefully cleaning the pigeon droppings that had accumulated in the antenna, but the noise did not go (Guth 23). They concluded that the noise was constant and it originated from outer space. This was one of the most successful predictions of the Big Bang theory and of universal expansion. Since then, there has been a rapid development of radio astronomy and numerous such telescopes have been developed throughout the world. The engineers were awarded the Nobel Prize in Physics for their discovery.
Immediately, radio telescopes became a success among astronomers. Radio telescopes gave a completely different view of the universe (Taylor 44). Since radio waves can pass through dense clouds of gas they can travel a greater distance than light. Therefore, radio astronomers have discovered objects that were not possible to discover using optical telescopes. The brightest stars visible through the optical telescopes are not at all bright in radio telescopes because radio telescopes pick up noise, not light. Astronomers have discovered "galaxy-like" objects at tremendous distances from the earth. These objects are extremely far away, about 10 billion light-years; where one light-year is the distance travelled by light in one year at a speed of 186,000 miles/sec. No objects have been discovered beyond these, therefore, it can be concluded that they are at the very edge of space and time, and their light barely reaches us (Eddington 228). When astronomers look at such objects, called quasars, they are looking directly back in time and hence into the Big Bang itself. Quasars are barely visible in optical telescopes but are noisy enough to be detected by powerful radio telescopes because they release an immense amount radio energy as compared to that released by a normal galaxy. As we look 10 billion years back in time, the sudden outcome of the Big Bang is clearly visible (Bergmann 25). In 1950, Radio astronomers found more sources of very powerful radio emission. These were galaxies that were so far away that they were invisible to optical telescopes but showed up as noisy specks only in radio telescopes. This observation is a vital proof of universal expansion that happened from the Big Bang (Taylor 60). In 1990 and 1992, NASA discovered that the microwave radiation comes from the Big Bang itself (Taylor 26). After a rigorous analysis of the radiation, scientists found tiny vibrations in the waves that clearly suggest that they came from an explosion. The explosion caused from the Big Bang. This meant that the unverse was definitely expanding.
Another important proof about the expansion of the universe came from the relative movement of the earth through space with respect to the constant microwave radiation (Wely 29). The radiation is so static that it can be assumed to be fixed in the outer limits of the universe and it travels in one direction. This property has enabled astronomers to calculate the motion of the earth through space by observing the frequency of the microwave radiation based on the Doppler effect. As with all waves, microwave radiation seems to have a dipole variation since it has a maximum and a minimum when viewed from a 180o angle. For example, if we are listening to a sound emitting source directly in front of us, we observe that the waves hit us directly in the face. If we turn 180o and listen again, the sound waves will be receding away from us. Similarly, radiation appears to approach earth from one direction and recedes in the exactly opposite direction. Moreover, there is a Doppler shift caused by the movement of the earth in space. This proves that the entire universe is moving away from some central point. This was also one of the most important proofs of universal expansion from the Big Bang.
The universe, therefore, is undoubtedly expanding. A galaxy one billion light-years away recedes half as fast as the one that is two billion light-years away. In a given time every galaxy increases its distance from every other by the same percentage (Born 55). A uniformly expanding universe may look roughly the same from any place in it.
From all the proofs of universal expansion, there have been numerous theories about the expansion of the universe. The most convincing of them all is the Big Bang theory. It states that at the dawn of time, when neither space nor matter existed, all the known matter was compressed into a Primeval Atom: a super-hot and super-dense object (Gribbin 18). The density of the Atom was tremendous roughly equal to that of a trillion suns compressed into a single proton. Temperature was infinite: not even protons existed as individual particles. The object exploded and created space and time as we know it. Even a million years after the explosion, the universe was too unstable and galaxies did not acquire their present shape. Empty space consisted of a uniform gaseous medium in which space and matter were at the same temperature. Tiny subatomic particles like electrons had such huge energies that a collusion of an electron with a bulldozer may have ripped the machine to shreds (Taylor 11). As time passed on, the universe became less and less dense and conditions became less inhospitable. Matter only existed as plasma, but as energy began to freeze, matter, as we know of it, began to form. The first matter formed was gas. Huge clouds of gasses were pulled together by gravitational force and the distance between individual clouds increased. As the temperature dropped, gasses became more and more compressed and arranged themselves into shapes that resembled present day galaxies; the first galaxies were created. Further, more complex interactions began to take place within the galaxies, and the distance between the individual galaxies increased. The young universe may have then seen the first star lights, as stars began to appear within galaxies releasing immense amounts of microwave radiation (Bergman 25). The temperature of empty space today in the universe is about 3K but the process of expansion in still continuing and microwave radiation is still coming from outer space (Taylor 226). Will the universe expand forever ? Nobody knows, however, the end of the universe has been anticipated as a Big Crunch (Taylor 53). As the universe reaches its outer limits of expansion, it will fall back on itself just as a ball thrown into the air falls back on earth due to gravity. The gravitational force will pull all existing matter back to the starting point: all our garbage will be recycled, and this will be followed by another Big Bang.
The Big Bang model is the most convincing model of the universe (Stenger 196). It has presented far more proof of universal expansion than any other model. The Big Bang model also accurately predicts the age of the universe. The age of the universe, previously calculated form the natural radioactivity of the Uranium238 atom, was about 10-15 billion years and the age calculated using the Big Bang model comes out to be the same (Cupra 93).
Conclusion
Confronted by such huge mysteries and unexplained phenomenon in the universe, man may never know the universal scheme in full detail (Cupra 360). There are still too many questions about the universe that remain unanswered, and are multiplying as we become more advanced (Stenger 197). We are only beginning to understand the behaviour of the universe, which still has to offer far more secrets than we can grasp. Rockets have been sent to the moon and the distant planets but space exploration still remains the final frontier for mankind. Will we ever reach the distant stars and galaxies to learn more about the universe ? Perhaps, we will stay here on our little planet trying to find solutions to the unsolved mysteries of the cosmos that have baffled us ever since we noticed the heavens.
Works Cited
The Riddle of Gravitation: Revised and Updated Edition
The Einstein Theory of Relativity
Physics and Chance: Philosophical Issues in the Foundations of Statistical Mechanics
Relativity for the layman: A simplified account of the history, theory, and proofs of relativity
The Tao of Physics: An Exploration of the Parallels between Modern Physics and Eastern Mysticism (25th Anniversary Edition)
Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity
The Inflationary Universe
In Search of the Big Bang
Introduction to Special Relativity
PSIence: How New Discoveries in Quantum Physics and New Science May Explain the Existence of Paranormal Phenomena
The Fabric of the Cosmos: Space, Time, and the Texture of Reality
Understanding Physics Today
Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law
Dark Side of the Universe: Dark Matter, Dark Energy, and the Fate of the Cosmos
Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimens ion
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