Understanding the universe that began from a primal void may be the greatest intellectual search ever. If the intellect of mere mortals seems too weak for the challenge, the imagination may be up to it. Cosmology and particle physics are both required to understand the evolution of the universe. Cosmology is the study of the birth and development of the universe, the largest entity known. Particle physics is the study of the basic building blocks of matter, the smallest entity known. The union of the two fields resulted in a scientific revolution.
The universe started with an enormous explosion, in which space, time, energy, and matter were created. There is almost complete agreement of this among scientists. The evidence that makes them so certain that the Big Bang model is correct comes from discoveries in astronomy and subatomic physics as well as astronomical observations based upon the analysis of light emitted from distant stars. Light is usually described as consisting of light waves. When raindrops intercept the sunlight, rainbow is produced with the familiar band of colors. Colors of the rainbow range from red, with lower frequency and longer wavelength, to violet, with higher frequency and shorter wavelength. A prism has the same effect of separating white light into its component colors. Many dark lines cross the spectrum of visible light. These lines are very important because the number and position of the lines reveals much information. Two dark lines surround each color. Spectroscopy is a process that separates light captured from distant stars or galaxies into its component wavelengths - its colors. By measuring how much light of various wavelengths and intensities an object emits over time, astronomers can determine many things: the object’s chemical composition; its temperature; its rotation; whether it is moving towards or away from Earth, and how fast; plus in many cases, its mass, its age and its distance from Earth.
The spectrum of waves extends from radio waves of one kilometer long (from crest to crest) to gamma rays with wavelength of a fraction of one-millionth of a millimeter. The visible light from the sun extends over a very small fraction of the spectrum of waves.
In 1912 the American astronomer Vesto M. Slipher (1875-1969), working at the Lowell Observatory in Arizona, discovered the "red shift," which paved the way to one of the greatest discovery in this century. All the dark lines in the visible part of the spectrum of all galaxies were shifted toward the red, and the lines in the red part of the spectrum are shifted into the infrared, and so on. This happens because the crests and troughs of the electromagnetic radiation are shifted towards the red, with the lower frequency, if the galaxy is moving away faster. This can be understood by a simple analogy. If you compress a coil spring, the number of coils in one inch will increase. But if you expand the coil spring, the number of coils in one inch will decrease. The number of coils in one inch is similar to the number of wave. Thus compression increases the frequency and expansion reduces it. In wave physics the shift towards the red end of the spectrum always indicates velocity of recession, i.e. moving away or expanding.
Another example to understand this is related to sound. Sound is pressure waves that excite the ear, when compressed against the ear and give the sensation of hearing. Suppose you are standing in a railway station, an express train is approaching at a high speed, with its whistle blowing. As it passes you, the pitch of the whistle drops suddenly. This has nothing to do with the whistling or your ear; it is due to the speed of the train. This can be explained as follows:
Suppose the speed of sound is 344 meters per second and that the approaching whistle is 344 meters away. Half a second later it is 172 meters away. Treat these as two separate instants, and you will see that the second sound reaches you, the stationary listener, only half a second later than the first. The wavelengths are being compressed because of the movement of the train is toward the listener. This is similar to the compression of a coil when it hits a wall. So the wavelengths are shortened, and the frequencies increase to a higher pitch. As the train passes the stationary listener, the process reverses, and each successive sound wave has a greater distance to travel. The interval between the successive peaks, therefore, is longer than the interval between their emissions, and accordingly, the pitch of the sound will be lowered. This is what is known as the Doppler effect.
The same thing applies to light waves, but in this case the speed is not that of sound, 344 meters per second, but of light, 300,000,000 meters per second. The instrument in this case is not the human ear, but the spectroscope, spreading out radiation into their color frequencies. The visual equivalence can be stated as follows:
1. An increase in auditory pitch (increase in frequency and decrease in wavelength) is a shift of the spectral lines towards the violet end of the spectrum, if the source is approaching the receiver.
2. A decrease in auditory pitch (decrease in frequency and increase in wavelength) is a shift of the spectral lines towards the red end of the spectrum, if the source is moving away from the receiver.
Figure 2.1 - Red Shift
A red shift, therefore, indicate the velocity of recession of the source, such as a star. If the faintness of a galaxy is accepted as an indication of its distance, and the red shift of the spectra as the velocity of recession, then the velocity of recession is proportional to the distance of the object. The further the star from us, the faster its speed of recession.
Figure 2.2 - Big Bang
The American astronomer Edwin Hubble (1889-1953) demonstrated that our galaxy is not the only one in the universe. In 1929 he announced the discovery of the linear relation between distant galaxies and their red shifts. This has been achieved by plotting the distance of some twenty-four relatively bright galaxies against their red shifts. He also gathered the first evidence that the universe is expanding. The red shifts of the much fainter and more distant galaxies are much higher. When he observed the distant galaxies moving away from Earth at a tremendous speed, they looked to him like they had been expelled in some primordial explosion. If their flight path could be run backward, they would unite into the original fireball. But the Big Bang got its enduring name when English astronomer Fred Hoyle, who believed the universe always had and always would exist in a "steady state," ridiculed the sudden birth notion. Hoyle suggested that the universe always looks the same from any viewpoint and at any time. Therefore, although galaxies are born, evolve and move away from each other, newly created matter, in the form of hydrogen gas continually replaces them, which evolve into galaxies and stars in due course. This means that the universe is in a state of constant creation of matter. The creation term is a misnomer, because as an atheist, Hoyle did not believe in God. His model suggested that the universe has no beginning and no end. He claimed the steady state theory explained the observed abundance of deuterium (a form of hydrogen), hydrogen, and helium, which are so successfully explained by the Big Bang. The steady state theory has now been completely abandoned by cosmologists - even by Hoyle himself.
There is doubt about precisely when the Big Bang happened. It was somewhere between 15 and 20 billion years ago. Recently, the Hubble space telescope was used to estimate the age of the universe. The question of the age of the universe is not only fascinating in its own right but also bears directly on just about every other cosmic mystery from the universe’s history to its eventual fate. The Hubble delivered its new verdict that suggested that the age of the universe is between 8 and 12 billion years. That may seem imprecise, but it was specific enough to throw astrophysicists into a state of high anxiety. The problem is that our own galaxy has stars believed to be 14 to 16 billion years old. And it makes astronomers uncomfortable to try to explain how stars could have been formed before the universe began. This uncertainty arises because it is unknown how tightly the universe is packed with matter. The gravity from high-density matter would have slowed the universe’s expansion considerably by now, meaning that the age of the universe could be closer to 8 billion years old. Most theorists think the density of the matter is indeed high, although observers have not been able to calculate exactly how high. Therefore, scientists may have to modify the details of the Big Bang.
However, among the astronomical observations that support the Big Bang, four strong evidences are important:
1. The first is that galaxies are all moving away from each other at a tremendous speed. Galaxies are observed using electronic detector attached to a telescope. The further the galaxy from us, the faster its speed of recession. Astronomers have detected this by the red shift in the galaxy’s spectrum. By measuring the red shifts, astronomers can determine the speed of recession of the galaxies. Since they know the further off they are the faster they move, they can calculate their distances. This is possible if we know exactly how the speed increases with distance. At the moment there is uncertainty about this. That is why the age of the universe is estimated to be 15 to 20 or 8 to 12 billion years. The ratio of the speed to distance - called Hubble constant - ranges between 15 to 30 kilometers per second per million light years. The speed is then determined from the red shift and the distance is determined using Hubble’s constant by simple calculation.
2. The second piece of evidence is the discovery in 1965 of radiation reaching us from every direction of the universe. These are similar to the electromagnetic radiation from light bulbs, from lightning flashes, and from any hot object. The discovery happened during the testing of a sensitive microwave receiver. This cosmic microwave background is of equal intensity from every part of the sky, and its maximum intensity occurs at a wavelength of 1.1 mm. What we are seeing is the glow of a primordial universe as it was at a very early date. Now, after about 15 billion years, this radiation has cooled to a few degrees above the absolute zero. This is the temperature to be expected today if the radiation had originated in an extremely hot Big Bang.
3. The third item of evidence of the Big Bang comes from nuclear physics. Studies of how the chemical elements would evolve after the Big Bang suggest that in the present day universe a ratio of deuterium and helium should be reached. Astrophysicists have verified that the existing ratio is what the theories predict.
The fourth evidence came in 1994, when NASA’s Cosmic Background Explorer satellite - COBE - discovered landmark evidence that the universe did in fact begin with the primeval explosion. In order for gravity to make galaxies out of atoms, it needs some chunks in the space in which the atoms are closer together, regions with greater than average density so that they could draw surrounding matter. And if they are present, they should be visible to a sensitive probe such as COBE in the form of warm and cool spots staining a microwave background. Indeed that is what happened. The signals from COBE shows a map of the sky with spots of all sizes indicating regions where the microwaves are minuscule 30 millionths of a degree warmer or cooler than the average. Scientist George Smoot, an astrophysicist at the university of California at Berkeley, when seeing the computer map, proclaimed:
"If you are religious, it is like looking at God"
The hypothesis of a primordial explosion is therefore extremely well founded. However, there are some variations of the theory. For now, there are not enough evidences for an alternative to the Big Bang, and the future may present another model of how the explosion started. Nevertheless, the Big Bang will remain one of the greatest constructs of the 20th century scientific thinking. It tells a story that spans for billions of years of the universe to an end that can only be assumed. One of those assumptions deals with whether or not the Big Bang is a cyclic phenomenon, with the universe alternately expanding and contracting like a spring forever, without a need for God! Even if the universe behaves like a spring, one should raise the perpetual question: Who started it?
At the birth of the universe, all matter and energy were compacted into an almost infinitely hot and infinitely dense point somewhere in a dark void. There was no space and no time. According to the theory of creation called inflation, the cosmos expanded at a furious rate in the first fractions of a second of existence. Then suddenly all the particles, energy, time, and space in the universe appeared. According to the Big Bang theory, a single point called a singularity, exploded spontaneously. This was not a burst of matter into space, but rather an explosion of the space itself. Mathematically speaking, singularity is defined as a point where no solution exists. A simple way to understand singularity is to try to divide a number, any number, by zero. The answer is infinity! But what is infinity? Infinity is a number that is larger than any number one can think of. If someone uses a calculator or a computer and tries to divide a number by zero, the result will be " error"!
The suggested steps for creating the universe can be described as follows:
1. The earliest moment that can be spoken of with certainty came after a period called the Planck time - the incredibly short time of 1E-43 second, a 1 preceded by 43 zeros or a ten millionth of a quadrillionth of a sextillionth second! At that time, the entire universe, which might have been only part of some unknown whole, was much smaller than an atomic nucleus. As suggested by calculation, 1E+20 as many as the universe at that time could fit in an atomic nucleus! All the four fundamental forces - gravitational, the strong and weak nuclear forces, and the electromagnetism - were combined together in one super force. The present theories fail to predict what happens in that short time, but they can be cautiously applied after the Planck time.
2. The next major event occurs after 1E-35 second, where the universe was propelled by the fragmented super force into the four basic forces. The universe inflated, not just expanded but doubling its size every 1E-35 second. Its borders (the space) rushed out at a speed that is faster than the speed of light (Einstein's theories may not allow matter or energy to travel through space faster than light, but they place no such restriction on space itself). During this inflation period from 1E-35 to 1E-33 second, the universe increased to about the size of a grapefruit. At this time, there were no atoms, but only quarks which constitute the nucleus of atoms, appeared as separate entities. Alan Guth at the Massachusetts Institute of Technology proposed this inflation model in the 1980s. The most startling part of inflation is the notion, as Guth puts it, "that the universe is a free lunch" - something comes from nothing.
3. At 1E-20 second after the Big Bang, cosmic strings, if they exist, would have formed and later served as seeds for galaxies. The laws of God observed today have emerged. Perhaps a small loop of strings attracted, with its gravity, enough matter to form a galaxy; a bigger loop might attract enough to form a galactic cluster. Cosmic strings seem to offer a good model for explaining the pattern of galaxies. Unfortunately, there is no evidence that strings exist.
4. At 1E-5 (0.00001) second, the universe was a soup of quarks, leptons, and radiation. It was cool enough for quarks to bind together in triplets to form protons and neutrons, the building blocks of atomic nuclei.
5. The Plasma period started three minutes later and simple atomic nuclei of heavy hydrogen, helium and lithium were formed. The name plasma is applied to a high temperature gas when the outer electrons became separated from their atoms. It is the plasma that glows inside a fluorescent tube or advertising sign. The universe was too hot for the atoms to hold together. They were ripped apart by the intense radiation as soon as they were created. The plasma period lasted for 300,000 years. The universe was like a dense smoke of free moving charged particles that light could not penetrate.
6. After 300,000 years simple atoms were formed when electrons were finally able to orbit protons without being immediately knocked out of their orbits by photons, the radiation or wave particles. The light that emitted during these atom formations is now the microwave background radiation that was detected in 1965. The universe became transparent to light. Theoretically, some areas were denser than others and thus were warmer and emitted more light. These areas later formed gas clouds or smoke.
7. From 300,000 to 2 billion years, under the influence of gravity, the colossal smokes gradually broke up into smaller galaxy-size structures.
8. After that, stars were formed in galaxies, and the universe continued to expand at a rate of 5 to 10 % every billion years.
In trying to explain the development of the universe, we are left with many unanswered questions:
1. What was there before the explosion started?
2. Why did the universe start at a very hot point?
3. Why did the universe start at a critical temperature and critical rate of expansion that separate models from collapsing as soon as it starts from those that go on expanding forever? After billions of years the universe is still expanding at almost the same rate. If the rate of expansion one second after the explosion had been smaller by even a part in a thousand billion billion, the universe would have been collapsed before it ever reached its present size.
4. What is the origin of the density fluctuations of the early universe that started the stars and galaxies?
The existing laws of physics offer no answer to the above questions. Those questions represent a great test of human faith or arrogance. Marc Davis from the University of California at Berkeley said:
"We all had to say that those were just God-given conditions"
This is one scientist that appreciates the limitations of the human knowledge. Other scientists introduce arrogant ideas when they encounter problems that they cannot hope to understand. They may blame God Himself for not revealing all of His secrets and His full list of laws in a way that everyone should understand. Some are even frustrated that they do not know all the laws that apply to the universe before 1E-20 second after the Big Bang. Steven Hawking, in his book "A Brief History of Time" writes in page 122:
"One possible answer is to say that God chose the initial configuration of the universe for reasons that we cannot hope to understand. This would certainly have been within the power of an omnipotent being, but if he had started it off in such an incomprehensible way, why did he choose to let it evolve according to laws that we could understand?"
Moreover, Hawking considers the Big Bang as a model that places limits on when and how God might have been carrying his job! In page 9 of the above-mentioned book, Hawking wrote:
"An expanding universe does not preclude a creator, but it does place limits on when he might have carried out his job!"
The late Carl Sagan of Cornell University of New York wrote in the introduction of this book:
"Hawking is attempting, as he explicitly states, to understand the mind of God. And this makes all the more unexpected conclusion of the effort, at least so far: a universe with no edge in space, no beginning or no end in time, and nothing for a Creator to do."
The above statement is elaborated in the same book in page 141.
Sagan’s idea is analogous to the creation story in Genesis, that God created the universe in six day, and then rested the seventh day. The suggestion here according to Hawking and Sagan that the seventh day is so long that it started right after the Big Bang and God is still resting and has nothing to do!
Now suppose, for the sake of argument, that two persons were brought together one from the seventh century and the other from the twentieth century. What may happen if the latter person were to explain the Big Bang and the theory of relativity to the former person? Could you visualize their discussion? The first person would appear extremely puzzled and incapable of understanding or believing the second person. Because we do not understand everything that God did or is doing, and because our existing knowledge fails to explain many of the mysteries of the universe, some of our present time scientists tend to think that the problem is not in our limitation, but in the limitation of God Himself.
The subject of evolution of the universe is a very complex one, and we do not know all the details of the Big Bang. With time, our knowledge will expand and we may improve on the existing model of the universe. Some Scientists may be disappointed that 90 to 99 percent of the universe is unknown to mankind. But, what else is new? Nearly, the same percentage of the human brain is unknown. We cannot determine the weather precisely, nor can we predict the location and intensity of the next earthquake.
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