There are a few flaws in the traditional Big Bang concept. The first is known as the flatness problem: why is the universe’s density so close to critical density, or, to put it another way, why is it so flat? The cosmos is currently so evenly divided between the positively-curved closed universe and the negatively-curved open universe that scientists are having trouble deciding which model to use. The current virtually flat condition stands out among all the options, ranging from extremely positively curved (extremely high density) to extremely negatively curved (extremely low density). Because any deviation from perfect equilibrium is compounded over time, the balance would have had to be considerably finer nearer the moment of the Big Bang. The cosmos would have re-collapsed by now if the universe density had been marginally more than the critical density a billion years after the Big Bang.
Consider how tough it is to shoot an arrow at a small target from a long distance. The arrow misses the target if your shot angle is slightly incorrect. As you travel further away from the objective, the allowed range of departure from the correct direction increases narrower and narrower. The more precisely calibrated the density had to be to get the universe’s current density so close to the critical density, the earlier in time the universe’s curvature became fixed. If the universe’s curvature had been only a few percent off from perfect flatness just a few seconds after the Big Bang, it would have either re-collapsed before fusion could begin, or it would have expanded so far that it would appear to be empty of matter. The density/curvature appears to have been finely tweaked.
Horizon Problem
The horizon problem is the second flaw in the traditional Big Bang model: why does the cosmos, particularly the microwave background, appear to be the same in all directions? The only way for two places to have the same circumstances (for example, temperature) is if they are close enough to share information and equilibrate to a common state. The speed of light is the quickest that information can travel. Two regions are isolated from each other if they are far enough apart that light hasn’t had enough time to travel between them. Because the regions cannot communicate with one another, they are said to be beyond their horizons (recall the term event horizon in the discussion about black holes).
Inflation
According to the inflation theory, any large-scale curvature of the section of the universe we can detect would have been expanded away by ultra-fast inflation. It’s like taking a little ball and blowing it up to the size of the Earth. Although the globe is still bent, the local section you’d view appears to be rather flat. The little universe has ballooned significantly, and the visible portion of the cosmos looks to be practically flat. That takes care of the flatness issue.
Inflation solves the horizon problem because regions that appear to be isolated from one another were in communication before the inflation period. They reached a state of balance before inflation pushed them apart. Another advantage is that the GUTs that predict inflation also predict an asymmetry between matter and antimatter, implying that matter should outnumber antimatter.
The origins of the ripples in the microwave background (the “galaxy seeds”) could potentially be explained by the inflation theory. Recall that matter-antimatter can transform to energy and energy can change back to matter-antimatter in an earlier section on the very early universe. Quantum mechanics, which deals with the very small scales of atoms, subatomic particles, and other particles, predicts that matter-energy fluctuations should be occurring at every point in space right now. It turns out that quantum fluctuations can happen if they happen fast enough to go unnoticed (the greater the energy-matter fluctuation, the quicker thefluctuation must occur). As a result, even in completely empty space (vacuum), there is a seething froth of fluctuations at very small scales, a vacuumenergy-virtual matter-antimatter virtual particles spontaneously emerging and then annihilating each other too swiftly for us to perceive. Although virtual particles-quantum foam may appear a little too fancy (to put it mildly), they do create measurable effects such as:
- The introduction of electron-positronvirtual particles in an atom will change the orbit of the real electron orbiting the nucleus, changing the energy levels that can be detected with extremely sensitive, precise equipment. When virtual particles are taken into account, the measured energy levels agree with those predicted by quantum mechanics.
- The presence of more virtual particles on either side of the plates than in the gap between the plates can explain the extra forces generated between close metal plates (the “Casimir Effect”).
- Collisions between genuine particles and antiparticles in high-energy particle accelerators can provide energy to the vacuum and induce the appearance of new particle-antiparticles.
Now let’s return to inflation. The galaxy seeds could have been quantum fluctuations in the early cosmos, but they would have been far too small to be the ripples we detect in the cosmic microwave background. That is, before inflation! The super-fast expansion of the cosmos during inflation would have stretched the fluctuations to considerably bigger sizes-large enough to create ripples in the microwave background that over billions of years became amplified to form galaxies under the influence of gravity. Although current versions of inflation theory cannot answer all of the questions about our universe’s large-scalestructures, they do predict a specific distribution of ripple sizes in the microwave background that is consistent with results from high-altitude balloon experiments, the WMAP mission, and the Planck mission. The temperature varies by around 1 part in 100,000, as anticipated by inflation, and the distribution of ripples peaks at an angular extent of one degree on the sky. Astronomers will examine how microwave background photons scattered off electrons right before the cosmos became transparent as they continue to evaluate data from the Planckspacecraft. Light becomes preferentially directed in a specific direction as a result of scattering (it is “polarized”). The most basic version of inflation predicts a specific polarization of the microwave background, which is visible in WMAP data. Scientists using WMAP and Planck will hunt for gravitational wave imprints from inflation, which would provide even stronger evidence for the inflation theory.
The much-heralded discovery of gravitational wave signatures in the microwave background by the Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) experiment at the South Pole in March 2014 turned out to be the result of an older incorrect model of microwave emission from our galaxy’s interstellar dust, which contaminates the cosmic microwave background. The BICEP2 team revealed their findings early to allow other research teams, notably those working at the South Pole and at the high elevations of the Atacama Desert in South America, to double-check their findings. Both have cold, dry air that is fairly consistent. The Planck and BICEP2 teams then collaborated to create the most accurate model of what signals from ancient gravity waves should look like, demonstrating in January 2015 that the previous announcement was erroneous. The hunt for gravitational wave imprints in the microwave background is still on!
The Cosmological Constant
Recent evidence suggests that the cosmological constant should be reinstated. Even when astronomers include the highest quantity of dark matter allowed by measurements, there is insufficient matter (luminous or dark) to flatten the universe-the cosmos is open with negative curvature if the cosmological constant is zero. According to the inflation theory, the universe should be flat to a great degree of precision. Beyond what ordinary and dark matter can do, an extra energy termed dark energy is required to make the universe curvature flat overall. The cosmic constant (vacuum energy) stated above is most likely this dark energy. The combined efforts of matter and dark energy flatten space as much as inflation theory predicts, according to recent studies of the cosmic microwave background.
The fact that quantum theory predicts that the total vacuum energy should be on the order of 10120 times greater than what is observed is a major stumbling block in the hypothesis of the cosmological constant. Quantum theory predicts that the cosmological constant will cause the universe to expand so quickly that you will be unable to see your hand in front of your face because light will not be able to reach your eyes! We can see billions of light years in actuality. Physicists are attempting to understand why the quantum theory’s prediction and reality are so far off. Some cosmologists are investigating the concept of “quintessence,” a dark energy that fluctuates with space and time. Keep an eye out for updates!
Two different teams made key observations of very distant (“high-Z”) Type Ia supernovae, which revealed that the expansion rate is slower than expected from a flat universe. Because they occur from the collapse of a star core of a specific mass, Type Iasupernovae are exceptionally bright and can be used as standard candles to measure very far distances (1.4 solar masses). Astronomers can determine the geometry of the cosmos by measuring extremely long distances. The supernovae were less bright than anticipated. After ruling out common theories like intergalactic dust, gravitational lensing, and metallicity effects, the two teams were forced to conclude that either the universe has negative curvature (is open) or that the supernovae are farther away than the Hubble Law says they are because the universe expanded more slowly than expected in the past. The supernova findings were shocking in that they revealed that the expansion is speeding fast! If only one team of astronomers had discovered this unexpected discovery, it would have been dismissed at the outset. The accelerating universe conclusion could not be discounted because two independent, extremely competitive teams (eager to prove the other team incorrect) discovered the same surprise outcome that was the polar opposite of their predictions. For their discovery, the two teams were awarded the Nobel Prize in Physics (in 2011). Other scientists have since proven that the universe’s expansion has been increasing for billions of years.
Without a repulsive cosmic constant to overcome gravity’s slowing impact, accelerating expansion is impossible. Because the expansion rate was slower long ago than it is now, an accelerating universe will raise the derivedage of the universe. The galaxies took longer to reach their great distances than predicted by the original decelerating universe model. Since everything was closer together long ago, gravity was the major force affecting the universe’s expansion. The gravitational effect became diluted as the cosmos expanded. The strength of gravity eventually fell below the amount of dark energy. Recent studies of how the rate of expansion has evolved throughout the universe’s history suggest that dark energy took over from gravity around 4 billion to 6 billion years ago, although its influence was not noticed until about 9 billion years ago.
The form that dark energy takes will determine the universe’s far future.
If dark energy is the cosmological constant, the universe’s expansion will continue for many trillions of years after all of the stars have died out. If dark energy is one of the probable forms of “quintessence,” the rate of acceleration accelerates, and galaxies, stars, and even atoms are ripped apart in a “bigrip” on a time scale before all stars die out (but after our Sun dies). After its current period of acceleration, other types of dark energy could lead the universe to re-collapse.
If the dark energy is a cosmological constant or a quintessence form, detailed studies of the microwave background and future observations of supernovae with betterdetectors, such as the Dark Energy Survey and new bigger space observatories, will inform us. The cosmological constant form is supported by data from the WMAP and Planck missions, as well as revised Hubble Constant measurements made with the Hubble Space Telescope. However, we have learnt enough from the past few years of unexpected observations to conclude that Einstein’s greatest blunder was admitting that he committed a blunder!
The Planck data has produced a huge conflict with Hubble Constant measurements. The Hubble Constant is 73.5 +/- 1.6 km/sec/Mpc, as determined through meticulous measuring of the distance scale ladder. The Planck derivation from cosmic microwave background radiation data is only 67.4 +/- 0.5 km/sec/Mpc. The lower number is supported by the eBOSS mapping of distant galaxies. Despite their proximity, the 6.1 km/sec/Mpc difference is substantially greater than the uncertainty. That could indicate unexpected complexities in dark energy or a new exotic particle (aside from whatever dark matter is) that needs to be added to the standard model of cosmology and particle physics, or that there’s something peculiar about our part of the universe that affects the expansion rate in a way we haven’t accounted for. Unfortunately, alterations to the standard model would throw off the standard model’s outstanding fit with other microwave background properties. The disparity will be resolved in the traditional scientific way: by cross-checking the studies, collecting more data, and making creative changes to our knowledge of the underlying physics.
The light we see from far things has been stretched by the expansion of space, and the distance between the distant object and us has been stretching as well, so how far away is that object from us now? It all relies on the Hubble Constant, Omega matter, and cosmological constant quantities you pick. To calculate the distance to that distant object, use Ned Wright’s Cosmology Calculator, and learn about the different terms for distance in an expanding universe, such as “comoving radial distance,” “angular size distance,” and “luminosity distance.” The AstroSims Cosmological Redshift Simulator is a simulation that shows how the distance between galaxies grows as light travels. The Hubble Constant is the lone variable in this simplified form of the expansion.
Review Questions
- In the mainstream Big Bang theory, what is the “flatness” problem? What makes you think it’s a fine-tuning issue?
- What is the Big Bang theory’s inflation extension, and when is it thought to have happened in the universe’s history?
- How does the inflation extension of the Big Bang theory explain the traditional Big Bang theory’s “flatness” and “horizon” problems?
- What is the “cosmological constant,” and why was it created by Albert Einstein? Why did Einstein call that a blunder? Why are cosmologists now claiming that it was not an error?
How can inflation help with the horizon problem quizlet?
Because it states that the Universe was all connected before inflation, it addresses the horizon problem. Inflation also solves the flatness problem by effectively flattening out any irregularities in the geometry of the early post-big-bang Universe, resulting in the flat Universe we witness today.
How does inflation theory solve monopole problem?
Consider living on a soccer ball’s surface (a 2-dimensional world). You may have noticed that this surface was curved and that you were in a closed universe. Even though it is still a spherical on bigger scales, if that ball grew to the size of the Earth, it would appear flat to you. Consider expanding the size of that ball to galactic proportions. Even though it may have been quite curved to begin with, it seems flat to you as far as the eye can see. Inflation flattens out any initial curvature of the three-dimensional world.
Because Inflation assumes a burst of exponential expansion in the early cosmos, distant places were actually considerably closer together before Inflation than they would have been with conventional Big Bang expansion.
As a result, previous to Inflation, such places could have been in causal contact and had a uniform temperature.
Magnetic monopoles can exist due to inflation as long as they were created before the period of inflation.
Because the density of monopoles decreases exponentially during inflation, their abundance decreases to undetectable levels.
Inflation also explains the creation of structure in the cosmos as a bonus.
Prior to inflation, the cosmos we can see today was microscopic, and quantum fluctuations in the quantity of matter on microscopic scales increased to astronomical scales during inflation.
The greater density regions condensed into stars, galaxies, and clusters of galaxies over the following several hundred million years.
How does the horizon problem fit into the inflationary universe model?
The cosmic inflation theory attempts to solve the problem by positing a 1032-second phase of exponential expansion in the first second of the universe’s history due to a scalar field interaction. The cosmos grew in size by a factor of more than 1022, according to the inflationary model, from a small and causally connected region in near equilibrium. Inflation then accelerated the expansion of the universe, isolating local parts of spacetime by expanding them beyond the boundaries of causal touch, essentially “locking in” the uniformity at great distances. Essentially, the inflationary model proposes that in the very early universe, the universe was totally in causal contact. After that, inflation extends the universe by about 60 e-foldings (the scale factor a increases by e60). The CMB is observed after a large-scale inflation has occurred. Because of the rapid expansion caused by inflation, it was able to maintain thermal equilibrium to this massive size.
The anisotropies in the Big Bang caused by quantum fluctuations are diminished, but not totally eliminated, as a result of cosmic inflation. Cosmic inflation smooths out differences in the temperature of the cosmic background, yet they still persist. The theory predicts a spectrum for microwave background anisotropies that is mainly consistent with WMAP and COBE data.
Quizlet: Which two problems in the cosmos can inflation theory solve?
The horizon and flatness difficulties are both solved by inflation theory. The Big Crunch would occur in a closed universe because which of the following forces acts as a brake on the universe’s expansion?
What is inflation theory?
Inflation is caused by an increase in the money supply, according to the monetary theory of inflation. Inflation rises faster as the money supply grows faster. In specifically, a 1% increase in the money supply leads to a 1% increase in inflation. The price level is proportional to the money supply when all other factors remain constant.
What does inflation theory imply?
The cosmos we live in was born around 14 billion years ago in an incredible event known as the Big Bang. The cosmos expanded exponentially in the first fraction of a second, expanding far beyond the perspective of today’s greatest telescopes. Of course, all of this is just speculation.
The BICEP2 consortium has announced the first direct evidence in favour of this notion, dubbed “cosmic inflation.” Their findings also include the first photos of gravitational waves, or space-time ripples. These waves have been referred to as the “Big Bang’s initial tremors.” Finally, the findings show that quantum physics and general relativity are inextricably linked.
“This is quite thrilling. We’ve captured the first direct image of gravitational waves, or ripples in space-time, across the primordial sky, confirming a theory about the universe’s birth “Chao-Lin Kuo, a co-leader of the BICEP2 collaboration and an assistant professor of physics at Stanford and SLAC National Accelerator Laboratory, said
The cosmic microwave background a faint glow left over from the Big Bang was observed by the BICEP2 instrument, yielding these ground-breaking results. The tiny oscillations in this afterglow reveal information about the early universe’s circumstances. Small temperature disparities throughout the sky, for example, reveal where the cosmos was denser, eventually condensing into galaxies and galactic clusters.
The cosmic microwave background exhibits all of the properties of light, including polarization, because it is a kind of light. The atmosphere scatters sunlight on Earth, causing it to become polarized, which is why polarized sunglasses can help minimize glare. The cosmic microwave background was dispersed and polarized in space by atoms and electrons.
BICEP2 co-leader Jamie Bock, a professor of physics at Caltech and NASA’s Jet Propulsion Laboratory, said, “Our team sought for a unique sort of polarization called ‘B-modes,’ which represents a twisting or’curl’ pattern in the polarized orientations of the ancient light” (JPL).
As gravitational waves move through space, they compress it, causing a characteristic pattern in the cosmic microwave background. Like light waves, gravitational waves have a “handedness” and can have left- and right-handed polarizations.
“Because of their handedness, the swirly B-mode pattern is a unique characteristic of gravitational waves,” Kuo added.
The researchers looked at sky scales ranging from 1 to 5 degrees (two to 10 times the width of the full moon). To accomplish this, they set up an experiment in the South Pole, where the cold, dry, and steady air allows for crisp detection of dim cosmic light.
BICEP2 co-principal investigator John Kovac, an associate professor of astronomy and physics at Harvard-Smithsonian Center for Astrophysics, who managed the project’s deployment and science operation, said, “The South Pole is the closest you can get to space while still being on the earth.” “It’s one of the world’s driest and clearest places, ideal for studying the faint microwaves left over from the Big Bang.”
The researchers were taken aback when they discovered a B-mode polarization signal that was far greater than many cosmologists had predicted. In order to rule out any inaccuracies, the team evaluated their data for more than three years. They also evaluated whether the apparent pattern may be caused by dust in our galaxy, but the data indicate that this is exceedingly unlikely.
“We were looking for a needle in a haystack, but we found a crowbar,” said Clem Pryke, an associate professor of physics and astronomy at the University of Minnesota.
In 1980, while a postdoctoral scholar at SLAC, physicist Alan Guth formally suggested inflationary theory as a revision of traditional Big Bang theory. Instead of beginning as a quickly expanding fireball, Guth proposed that the cosmos grew exponentially larger in a fraction of a second after exploding from a tiny portion of space. This concept drew a lot of interest right on since it seemed to offer a novel answer to many of the problems with the standard Big Bang theory.
Certain predictions in Guth’s scenario, however, contradicted empirical facts, as Guth, who is now a professor of physics at MIT, quickly realized. In the early 1980s, Russian physicist Andrei Linde tweaked the model to create “new inflation” and then “eternal chaotic inflation,” both of which produced forecasts that matched actual sky observations.
Linde, who is now a professor of physics at Stanford, couldn’t contain his joy at the news. “These data represent a smoking gun for inflation,” he added, explaining that other theories do not foresee such a signal. “This is something I’ve been waiting 30 years to witness.”
BICEP2’s measurements of inflationary gravitational waves combine theoretical reasoning with cutting-edge technology in a stunning way. Beyond Kuo, who designed the polarization detectors, Stanford had an important role in the discovery. Kent Irwin, a physics professor at Stanford and SLAC, worked on the superconducting sensors and readout devices that were employed in the experiment. Kuo, who is connected with the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), which is financed by Stanford, SLAC, and the Kavli Foundation, was one of the researchers participating in the study.
BICEP2 is the second stage of the BICEP and Keck Array experiments, which are part of a coordinated program with a co-principal investigator organization. Jamie Bock (Caltech/JPL), John Kovac (Harvard), Chao-Lin Kuo (Stanford/SLAC), and Clem Pryke (Stanford/SLAC) are the four principal investigators (UMN). All of them, as well as excellent student and scientist teams, collaborated on the current result. University of California, San Diego; University of British Columbia; National Institute of Standards and Technology; University of Toronto; Cardiff University; and Commissariat l’nergie Atomique are among the primary BICEP2 collaborators.
The National Science Foundation is funding BICEP2 (NSF). The National Science Foundation also manages the South Pole Station, which houses BICEP2 and the other telescopes employed in this study. The Keck Foundation also contributed significantly to the team’s telescope building. The construction of the ultra-sensitive detector arrays that enabled these measurements was generously financed by NASA, JPL, and the Moore Foundation.
What is the cosmic inflation theory?
The notion of exponential expansion of space in the early cosmos is known as cosmic inflation, cosmological inflation, or just inflation in physical cosmology. From 1036 seconds after the conjectured Big Bang singularity to somewhere between 1033 and 1032 seconds following the singularity, the inflationary epoch lasted. The cosmos continued to grow after the inflationary epoch, but at a lesser rate. After the universe was already over 7.7 billion years old, dark energy began to accelerate its expansion (5.4 billion years ago).
Several theoretical physicists, including Alexei Starobinsky at the Landau Institute for Theoretical Physics, Alan Guth at Cornell University, and Andrei Linde at the Lebedev Physical Institute, contributed to the development of inflation theory in the late 1970s and early 1980s. The 2014 Kavli Prize was awarded to Alexei Starobinsky, Alan Guth, and Andrei Linde “for pioneering the hypothesis of cosmic inflation.” It was further improved in the early 1980s. It describes how the universe’ large-scale structure came to be. The seeds for the growth of structure in the Universe are quantum fluctuations in the microscopic inflationary zone, enlarged to cosmic scale (see galaxy formation and evolution and structure formation). Inflation, according to many physicists, explains why the world appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is dispersed uniformly, why the cosmos is flat, and why no magnetic monopoles have been found.
The precise particle physics mechanism that causes inflation remains unclear. Most physicists accept the basic inflationary paradigm since a number of inflation model predictions have been confirmed by observation; nonetheless, a significant minority of experts disagree. The inflaton is a hypothetical field that is supposed to be responsible for inflation.
In 2002, M.I.T. physicist Alan Guth, Stanford physicist Andrei Linde, and Princeton physicist Paul Steinhardt shared the renowned Dirac Prize “for development of the notion of inflation in cosmology.” For their discovery and development of inflationary cosmology, Guth and Linde were awarded the Breakthrough Prize in Fundamental Physics in 2012.
Which of the following methods can be used to combat the horizon effect?
The horizon effect, also known as the horizon problem, is produced by the search algorithm’s depth constraint and manifests itself when a negative event is unavoidable but can be postponed. Because only a portion of the game tree has been examined, the algorithm will believe that the event may be avoided when this is not the case. Extensions, particularly check extensions, are aimed to lessen horizon effects in addition to the mandatory quiescence search.
For practical reasons, search depth is limited when analyzing a big game tree using strategies like minimax with alpha-beta pruning. However, analyzing an incomplete tree can produce erroneous results. When a substantial change occurs just outside the search depth’s horizon, the computing device is affected by the horizon effect.
In 1973, Hans Berliner coined the term “Horizon Effect” to describe a phenomenon that he and other academics had seen. The Negative Horizon Effect “results in the creation of diversions that ineffectively delay an unavoidable outcome or make an impossible one appear achievable,” according to him. “The program grabs much too soon at a consequence that can be enforced on an opponent at leisure, frequently in a more effective form,” according to the “mostly unnoticed” Positive Horizon Effect.
The horizon effect can be reduced by adding a quiescence search to the search algorithm. This allows the search algorithm to examine beyond its horizon for a certain class of moves that are critical to the game state, such as chess captures.
Many horizon effect concerns can be solved by rewriting the evaluation algorithm for leaf nodes and/or studying more nodes.
The horizon effect can be solved using which of the following techniques?
A flat Universe is one in which the amount of matter present is just enough to stop the expansion of the universe but not enough to collapse it. This would be an extremely delicate balancing act! Imagine astronomers’ amazement when they discovered that, as far as we can tell, the Universe had exactly the density of matter required to be flat. The ‘flatness problem’ has sprung up as a result of what appears to be a genuinely astonishing coincidence.
To put it another way, the flatness problem occurs because we appear to dwell in a Universe with a density parameter (0) that is very close to one. To put it another way, the Universe is on the verge of reaching critical density. The ‘issue’ is that, after 14 billion years of expansion and evolution, the Universe must have been even closer to critical density at some point in the past. For example, during Planck time (within 10-43 seconds of the Big Bang), the density must be within 1 part in 1057 of the critical density. i.e. 0 had to have been almost accurate at first:
There is no known explanation for the Universe’s density to be so near to the critical density, and most astronomers see this as an excessively weird coincidence.
As a result, there is a ‘issue’ with flatness.
Many ideas have been proposed to explain the flatness problem, and recent theories now include the theory of inflation, which predicts the Universe’s observable flatness.
However, not all scientists embrace inflation, and the topic continues to be a source of discussion and inquiry.