Alan Harvey Guth
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Alan Harvey Guth (born February 27, 1947 in Perth Amboy, New Jersey) is a theoretical physicist and cosmologist.
Guth has researched elementary particle theory (and how particle theory is applicable to the early universe). Currently serving as Victor Weisskopf Professor of Physics at the Massachusetts Institute of Technology, he is the originator of the inflationary universe theory.
He graduated from MIT in 1968 in physics and stayed to receive a master's and a doctorate, also in physics.
As a junior particle physicist, Guth first developed the idea of cosmic inflation in 1979 at Cornell after attending a Big Bang lecture by Robert Dicke, and gave his first seminar on the subject in January 1980. Moving on to Stanford University Guth formally proposed the idea of cosmic inflation in 1981, the idea that the nascent universe passed through a phase of exponential expansion that was driven by a positive vacuum energy density (negative vacuum pressure). The results of the WMAP mission in 2006 made the case for cosmic inflation very compelling.
Alan Guth was born on February 27, 1947 in New Brunswick, New Jersey, USA to the middle-class, Jewish couple Hyman and Elaine Guth, owners of a small grocery store and a dry-cleaning establishment. Unlike their son, they were not highly educated: Hyman had only graduated from junior college, while his wife never went to college. Guth was the middle child between two sisters, Arlene his older sister by three years, and the younger by six years of which is Lucille. He has stated that in his mostly uneventful childhood, he developed a great fondness for mathematics.
After attending several public schools, he skipped his senior year to start at the Massachusetts Institute of Technology. After his junior year, he enrolled in a five-year program where he could get his bachelor’s and master’s after two more years. MIT was easier for him than high school because all his courses were science and math. One reason he did this was because he was worried about the draft. He certainly was not a big fan of the Vietnam War, because in 1970 he participated in some speeches at political activities. Guth managed to obtain both a bachelor’s and master’s degree in 1969 and a doctorate in 1972. In 1971, he married Susan Tisch, his high school sweetheart, and they had two children: Lawrence (born 1977) and Jennifer (born 1983). However, Guth found a hard time finding a permanent job before he found his true calling in investigating the origins of the universe. Part of the problem was that the assistant professorships at the universities were filled, largely because of the baby boom.
At the very beginning, Guth did not have much interest in cosmology and tended to focus on particle physics. After he graduated in 1971, he spent nine years traveling across the country pursuing temporary postdoc jobs related to physics hoping to get a permanent job at a university somewhere, but did not meet much luck. He was at Princeton 1971 to 1974, Columbia 1974 to 1977, Cornell 1977 to 1979, and the Stanford Linear Accelerator Center (SLAC) 1979 to 1980.
Guth's earliest work at Princeton was in the study of quarks, the elementary particles that made up protons and neutrons. His research became obsolete with the development of the theory of quantum chromodynamics, which gave quarks a new special property called color. Ironically, much of that theory had been developed by graduate students at Princeton, but Guth had been too wrapped up in his own ideas to notice what was going on around him. When Guth discovered this he felt embarrassed that he was paying no attention to what his colleagues were doing. Since his time at Princeton had been wasted, he had to find another postdoc job in any way that was available to him, such as reading notices on bulletin boards and called acquaintances who worked in physics departments. He eventually was able to get another postdoc job at Columbia, where he attempted to catch up in particle physics.
In his new job, Guth studied gauge theory, which was the basic idea behind quantum chromodynamics. He worked on the idea that symmetry in the universe had broken down. Steven Weinberg, who would later have an influence on Guth, had developed the electroweak theory, which was the idea that the weak nuclear force and electromagnetism were once the same force shortly after the Big Bang, when the universe was at a very high temperature. When the two forces became separate, there was spontaneous breaking of symmetry. Weinberg suggested that when symmetry breaks down, the universe goes through a phase transition similar to when water turns into ice or steam. Guth started studying the details of phase transitions.
One of the things Guth focused on was magnetic monopoles, which were believed to exist somewhere in the universe, but had yet to be found by anyone. Monopole magnets were initially predicted by Maxwell’s equations, which united electricity with magneticism. While magnets with a north and south pole had been observed, there was no scientific law that prevented the appearance of magnets with only one pole. In the process of spontaneous symmetry breaking, very tiny discontinuities would be produced with the properties of monopoles. Guth became an expert on the topic of monopoles.
Guth's first step to developing his theory of inflation occurred at Cornell in 1978, when he heard a lecture by Robert Dicke about the flatness problem of the universe. Dicke explained how the flatness problem showed that something significant was missing from the Big Bang theory at the time. The fate of the universe depended on its density. If the density of the universe was large enough, it would collapse into a singularity, and if the actual density of the matter in the cosmos was lower than the critical density, the universe would increasingly get much bigger.
The next part in Guth's path came when he saw a lecture by Steven Weinberg in early 1979. Weinberg talked in two lectures about the Grand Unified Theory (GUT) that had been developed since 1974, and how it could explain the huge amount of matter in the universe compared to the amount of antimatter. The GUT explained all the fundamental forces known in science except for gravity. It established that in very hot conditions, such as those after the Big Bang, electromagnetism, the strong nuclear force, and the weak nuclear force were united to form one force. Weinberg also was the one who emphasized the idea that the universe goes through phase transitions, similar to the phases of matter, when going from high energy to low energy. Weinberg’s discussion of why matter is so dominant over anti-matter showed Guth how precise calculations about particles could be obtained by studying the first few seconds of the universe.
Guth decided to solve this problem by suggesting that a supercooling during a delayed phase transition. This seemed very promising for solving the magnetic monopole problem. By the time they came up with that, Guth had gone to the Stanford Linear Accelerator Center for a year, but Guth had been talking to Henry Tye back and forth. Tye suggested that they check that the expansion of the universe not be affected by the supercooling. In the supercooled state, a false vacuum is produced. The false vacuum is a vacuum in the sense that it is state of the lowest possible density of energy; it is false in the sense that it is not a permanent state of being. False vacuums decay, and Guth was to find that the decay of the false vacuum at the beginning of the universe would produce amazing results, namely the exponential expansion of space.
Guth realized from his theory that the reason why the universe appears to be flat was because it was fantastically big, just the same way the spherical Earth appears flat to those on its surface. The observable universe was actually only a very small part of the actual universe. Traditional Big Bang theory found values of omega near one to be puzzling, because any deviations from one would quickly become much, much larger. In inflation theory, no matter where omega starts, it would be driven towards equal to one, because the universe becomes so huge. In fact, a major prediction of inflationary theory is that omega will be found to be one.
The reason for the missing monopoles was that the universe was so big that the density of monopoles would be very low. The “enormous number of monopoles could have risen in the inflationary universe, yet we and all other observers would find them to be observationally far rarer than snowballs in the Sahara…Inflation would spread them so thin that the average observer would expect to find only a single monopole in the entire observable universe.” The incredibly vast expansion of the universe caused by inflation solved both the flatness problem explored by Robert Dicke and the monopole problem that had been explored by Tye and Guth.
By an amazing coincidence, two weeks later, Guth heard about another problem discussed by colleagues at work. This was called the horizon problem. The microwave background radiation discovered by Arno Penzias and Robert Woodrow Wilson appeared extremely uniform, with almost no variance. This seemed very paradoxical because, when the radiation was released about 300,000 years after the Big Bang, the observable universe had a diameter of 90 million light-years. There was no time for one end of the cosmos to communicate with the other end, because energy can not move faster than the speed of light. The paradox was resolved, as Guth soon realized, by the inflation theory. Since inflation started with a far smaller amount of matter than the Big Bang had presupposed, an amount so small that all parts would have been in touch with each other. Inflation then blew up the universe so quickly that there was no time for the essential homogeneity to be broken. The universe after inflation would have been very uniform even though the parts were not still in touch with each other.
Guth first released his ideas on inflation in a seminar at SLAC on January 23, 1980. Word about his ideas spread quickly and soon Guth, who had been worried about his job prospects, was besieged with offers. Although there were positive responses from his audiences, Guth did not publish his work because he was primarily concerned with the “graceful exit” problem. In August, he submitted his paper, entitled “The Inflationary Universe: A Possible Solution to the Horizon and Flatness Problems” to the Physical Review. He ignored magnetic monopoles because they were based on assumptions of GUT, which was outside the scope of the speech.
The answer came on December 1981 while Guth was finishing a paper on his failures. He read a paper from Moscow physicist Andrei Linde saying that the whole universe is within just one bubble, so nothing is destroyed by wall collisions. This conclusion was made using a Higgs field with an energy graph that was originally proposed by Sidney Coleman and Erick Winberg. Guth was amazed by this concept so he searched through Linde’s paper looking for a blunder, but he found none. Linde had independently been working on bubble inflation, but no one had informed him of the flatness problem. Both he and Guth eventually exchanged papers, thus helping each other work out inflation. Another person who was working on the “graceful exit” problem was Paul Steinhardt.
While inflation was a very interesting theory that was able to solve some existing problems in cosmology, it still needed to be tested. Scientists decided to find out if there is the amount of variation in the background inflation that was predicted by inflationary theory. To accomplish it, they sent two probes to measure the non-uniformities that Guth and Linde said could be found. The results of the first, COBE (Cosmic Background Explorer) were released in 1992 and said “yes.” However, the physicists who sent it felt that they needed to modify their estimates of the experimental uncertainties. COBE was followed in 2003 by WMAP (Wilkinson Microwave Anistropy Probe), which showed that the nonuniformities did exist with even greater precision. This helped show that Guth’s ideas on inflation were the correct ones.
An even more critical test for inflation was: is the value of omega precisely one? According to Guth's inflation theory, omega for the observable universe should equal one, even though it would most likely be much different for the entire universe. In 1998, they accomplished this by measuring the movements of Type Ia supernovae. One thing that they noticed was the supernovae were all the same. They also found out that distant objects actually moved slower than scientists had expected according to Hubble’s expansion law. This suggested the existence of dark energy existing in empty space responsible for the expansion rate of the universe. It was determined from the supernova projects that omega almost certainly equals one, which was in perfect consistency with the inflation model.
Creating a new universe
Guth has investigated the conditions for how a universe could be created in a laboratory, consistent with the laws of physics. Traditionally, one would need the energy of several galaxies, but inflation theory showed it is actually much easier to create a universe. All one needs is one ounce and false vacuum. Once false vacuum exists, the evolution of the universe is independent of what came before. Physicist Roger Penrose once stated that one would need negative energy to create a new universe, but Guth showed that it could also be made by quantum tunneling.
The birth of a new universe also does not affect the old one. It would take about 10−37 seconds to disconnect from its parent. However, all an observer would see is the formation of a black hole, which would disappear very quickly. Creating a new universe actually would be quite dangerous since it would result in the release of energy similar to that of a 500 kiloton explosion.
Alan Guth believes that the size of the entire universe is at least 1023 times bigger than the size of the observable universe. The universe also exists among countless other universes with various different laws of physics. A fractal pattern exists in the multiverse system, which involves universes inside vacuums that are inside other universes. Each pocket universe created by inflation will appear flat to the observers within it. Meanwhile, new universes will fill in the gaps created by older ones, similar to Hoyle’s discredited steady-state theory. The big bang of the universe is actually similar to cell division in biology, since new universes are continuously formed. However, inflation always wipes out the circumstances of the beginning of the particular universe.
Alan Guth's main beliefs about the universe are that it definitely has a beginning and that it is just one of many universes that came into existence. Inflation never ends, but keeps expanding at an exponential rate, meaning that it doubles in very short increments much less than one second. Universes keep being created all the time as bubbles within the inflation process. The entire cosmos was created by quantum fluctuations from nothingness. While the concept of a universe being created from nothing sounds improbable, it is perfectly consistent with the laws of conservation of energy because its total energy value is zero.
One theory that Guth is particularly fond of is string theory, which says that the building blocks of the universe are superstrings that are much smaller than elementary particles. According to the latest versions of this theory, there are about 10500 possible vacuums in existence. The main reason why Guth supports string theory is that he feels that it is the only one that provides a working idea of quantum gravity, a concept that physicists have long been searching for.
There have been more than fifty additional inflation theories proposed since Guth's original model. Now that the Planck spacecraft was finally launched in 2009, it should provide data to help choose between the various theories of the details of inflation. The theory of inflation that wins out will certainly differ from Guth's original model, which he acknowledged was incomplete because of its inability to solve the "graceful exit" problem. But Guth will always be remembered as the person who revealed inflationary theory to the scientific community.
According to Guth’s theory of cosmic inflation, the universe originated from a false vacuum filled with high energy. The existence of a repulsive gravitational field caused the universe to enter a great period of exponential expansion. He realized that the expansion was so quick that in only 10−33 seconds, it was 1050 times the original size. Due to the fact that the false vacuum is not stable, the expansion will not continue forever. Instead, quantum tunneling will cause the false vacuum to decay into a low-energy true vacuum. When it decays, bubbles suddenly appear to fill in the space. Although the bubble universes start out small at first, many of them will quickly become fairly large. The ultimate conclusion was that, on the contrary to popular belief, it was possible for the universe to suddenly appear from nothing.
Guth is the Victor F. Weisskopf Professor of Physics at the Massachusetts Institute of Technology (MIT). So far, he has written about 60 technical papers related to the effects inflation and its interactions with particle physics. He has won many awards and medals, including the Medal of the International Center for Theoretical Physics, Trieste, Italy, with Andrei Linde and Paul Steinhardt and the Eddington Medal in 1996, and the 2009 Isaac Newton Medal, awarded by the British Institute of Physics.
* "It is said that there's no such thing as a free lunch. But the universe is the ultimate free lunch". — A. H. Guth