Cosmic Inflation
Cosmic Inflation is a theoretical framework that proposes a rapid expansion of the universe occurring shortly after the Big Bang. Initially introduced by physicist Alan Guth in 1980, this theory emerged to address several shortcomings of the Big Bang model, such as the flatness, horizon, and magnetic monopole problems. Unlike the steady expansion suggested by the Big Bang, Cosmic Inflation posits that the universe underwent exponential growth, allowing it to achieve a nearly flat geometry and maintain thermal equilibrium across vast distances.
The theory also offers insights into the formation of stars and galaxies, suggesting that the initial building blocks of these structures were microscopic and expanded significantly during inflation. Evidence supporting Cosmic Inflation includes observations of gravitational waves in the cosmic microwave background radiation, though subsequent data raised questions about these findings. Visual analogies often liken Cosmic Inflation to inflating a balloon, where the initial rapid inflation shapes the universe and influences its properties. As research continues, Cosmic Inflation remains a crucial concept in understanding the origins and evolution of the universe.
Cosmic Inflation
FIELDS OF STUDY: Astrophysics; Theoretical Astronomy; Cosmology
ABSTRACT: The big bang theory states that the universe developed slowly after the initial burst that created it. In contrast, cosmic inflation is a theory that says there was a short, intense period of expansion immediately afterward. This explains the flatness, horizon, and magnetic monopoles problems with the big bang theory.
Origins of Cosmic Inflation
The idea that the universe had a specific beginning in a sudden burst has its origins in the thoughts of ancient astronomers. Advancements in technology helped refine those ideas into the big bang theory. However, as researchers began to study the universe in more detail, they discovered some problems with the theory. Some phenomena that should have been associated with the big bang were absent, while others were present that the theory did not explain.
In 1980, physicist Alan Guth (b. 1947) proposed a theory to address some of those issues. Guth’s theory had a few errors, but fellow physicists Andreas Albrecht (b. 1957), Andrei Linde (b. 1948), and Paul Steinhardt (b. 1952) soon added further research and information. These four men are considered to be the architects of the cosmic inflation theory.
Building on the Big Bang
Scientists in the field of cosmology and astrophysics study the universe for clues to its origin. They have discovered several clues that are compatible with the predictions of the big bang theory. For example, researchers predicted in 1948 that the big bang should have left behind heat in the form of cosmic microwave background radiation (CMB), which would produce a blackbody spectrum. In 1965, this was found to be true. The theory also predicted the early formation of light elements, which researchers were also able to prove.
However, there were several problems with the big bang theory. Three of these are the flatness problem, the horizon problem, and the magnetic monopole problem. The flatness problem is so called because, according to the theory, the universe should have continued to curve as it expanded, but cosmologists determined that it is nearly flat. The horizon problem refers to the near-uniformity of the CMB throughout the universe. All CMB produces a blackbody spectrum characteristic of a specific temperature—about 2.7 kelvins—which suggests that when it was first emitted, the universe was a constant temperature throughout. However, the horizons of the observable universe would have been too distant from one another to reach thermal equilibrium. The time required for information to travel that far was greater than the age of the universe. Finally, the theory predicted the existence of a large number of magnetic monopoles, while no such particle has ever been found.
The theory of cosmic inflation addresses all these issues. While the big bang theory proposed that the universe expanded at a steady rate, cosmic inflation theory says that there was first a short period of rapid inflation. During this period, the universe grew exponentially, expanding faster than the speed of light, before losing energy and slowing its growth. This accounted for the flatness problem: the initial expansion altered the universe’s shape from the expected sphere into something that appears flatter. It also meant that when the CMB was produced, the now-distant reaches of the universe would have been much closer together than previously thought—close enough to reach thermal equilibrium before being separated by inflation. Cosmic inflation also suggests that magnetic monopoles were formed shortly after the big bang but were then spread so far and wide by inflation that they have yet to be detected.
Cosmic inflation theory also helps explain the formation of stars and galaxies. It says that the building blocks of these stellar features were microscopic until inflation expanded them exponentially. The areas that maintained the highest densities of the original matter of the universe formed stars, galaxies, and galaxy clusters.
Evidence of Cosmic Inflation
In March 2014, scientists using the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope in Antarctica said they had detected gravitational waves in the CMB. The BICEP2 team believed these waves showed that inflation had occurred, validating the theory. However, in January 2015, information from the European Space Agency’s (ESA) Planck satellite reported a large dust cloud in the Milky Way galaxy that was found to have caused some or all of the gravitational waves. However, the BICEP2 team continued its research and the hunt for information about the origins of the universe continues.
Visualizing Cosmic Inflation
The effects of cosmic inflation can be broadly likened to the inflation of a balloon. The first puff of air causes a rapid change in the size and shape of the balloon, after which it grows more gradually as it inflates. This accounts for why the universe remains flat and has not grown rounder: it is maintaining the shape it gained during the initial inflation period. The theory explains how parts of the universe can have such similar properties, since they were once much closer together, just as the ink of a design drawn on the balloon would have consistent properties even after the balloon was inflated. The increasing size of the universe would also allow for any monopoles to be scattered widely, just as dots drawn on the balloon would spread farther apart as the balloon expanded.
While scientists continue to study the universe for clues to its formation, cosmic inflation provides an important way to understand how the universe formed as it did.
Principal Terms
- Alan Guth: an American theoretical physicist who first proposed the theory of cosmic inflation in 1981.
- Andreas Albrecht: an American cosmologist and theoretical physicist, considered a co-architect of the cosmic inflation theory.
- Andrei Linde: a Russian-born physicist who revised Guth’s work; one of the co-architects of cosmic inflation theory.
- big bang theory: a widely accepted explanation of the origin of the universe that says the universe was formed by the sudden expansion of a very hot, dense primordial fireball about 13.7 billion years ago.
- blackbody spectrum: the range of wavelengths of thermal radiation given off by a blackbody, an object that neither reflects nor transmits received light but gives off some light at all wavelengths, with shorter wavelengths for hotter objects.
- cosmic microwave background radiation: thermal radiation that is present in nearly uniform quantities throughout the observable universe and produces a blackbody spectrum characteristic of a temperature of approximately 2.7 kelvins. It believed to be left over from an early stage of universe expansion..
- cosmology: the astrophysical science that seeks to understand why the universe is the way it is by looking at how it formed, how it has changed, how it is structured now, and how it may change in future.
- flatness: a point of near-critical density, or the point at which the universe stops expanding.
- horizon: the limit of the observable universe, or the farthest region of the universe from which Earth can receive information (i.e., radiation), located about forty-five billion light-years away.
- light element: one of the first three elements of the periodic table—hydrogen (in the form of the isotope deuterium), helium, and lithium—which are believed to have been formed within the first few minutes of the big bang.
- magnetic monopole: a hypothetical magnetic particle that has only a north pole, unlike ordinary magnets, which have both a north and a south pole.
- Paul Steinhardt: an American physicist and cosmologist who was one of the co-architects of cosmic inflation theory; also proposed the cyclic model, which hypothesizes that the universe develops in cycles and that some events important to the formation of the universe happened before the big bang.
Bibliography
"Beyond Big Bang Cosmology." Wilkinson Microwave Anisotropy Probe.NASA, 16 Apr. 2010. Web. 22 Apr. 2015.
Connolly, Amy R. "Scientists: Evidence of Big Bang Theory Fails to Space Dust." UPI.com. United P Intl., 31 Jan. 2015. Web. 22 Apr. 2015.
"Cosmic Microwave Background." Cosmos: The SAO Encyclopedia of Astronomy. Swinburne U of Technology, n.d. Web. 22 Apr. 2015.
"Cosmology: The Study of the Universe." Wilkinson Microwave Anisotropy Probe. NASA, 21 Dec. 2012. Web. 22 Apr. 2015.
"The Origins of the Universe: The Big Bang." The Stephen Hawking Centre for Theoretical Cosmology.U of Cambridge, n.d. Web. 22 Apr. 2015.
Palma, Christopher. "Blackbody Radiation." Astronomy 801: Planets, Stars, Galaxies, and the Universe. Penn State U, 2014. Web. 22 Apr. 2015.
Sutter, Paul. "Seeing the 'Real' Big Bang Through Gravitational Waves." Space. Future US, 25 July 2021, www.space.com/big-bang-study-with-gravitational-waves. Accessed 14 June 2022.