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.
In astronomy, what causes inflation?
That phase of rapid, accelerated expansion is propelled by a new character to enter the cosmological cast: something termed the inflaton, according to our present idea of cosmic inflation. Is that clear? The inflaton fills with air.
What is the 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.
Flatness Problem
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?
What does cosmic inflation entail? How does inflation address the horizon problem in the quizlet on the flatness problem?
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.
What causes price increases?
- Inflation is the rate at which the price of goods and services in a given economy rises.
- Inflation occurs when prices rise as manufacturing expenses, such as raw materials and wages, rise.
- Inflation can result from an increase in demand for products and services, as people are ready to pay more for them.
- Some businesses benefit from inflation if they are able to charge higher prices for their products as a result of increased demand.
What is an example of inflation?
You aren’t imagining it if you think your dollar doesn’t go as far as it used to. The cause is inflation, which is defined as a continuous increase in prices and a gradual decrease in the purchasing power of your money over time.
Inflation may appear insignificant in the short term, but over years and decades, it can significantly reduce the purchase power of your investments. Here’s how to understand inflation and what you can do to protect your money’s worth.
What occurs during a period of inflation?
The Inflation Theory proposes that the universe experienced a period of extremely rapid (exponential) expansion in its early beginnings. It was created about 1980 to explain a number of issues with the traditional Big Bang theory, which states that the cosmos expands slowly over time.
What does inflationary imply?
Inflation is the gradual loss of a currency’s buying value over time. The increase in the average price level of a basket of selected goods and services in an economy over time can be used to calculate a quantitative estimate of the rate at which buying power declines. A rise in the general level of prices, which is frequently stated as a percentage, signifies that a unit of currency now buys less than it did previously.