In the field of Cosmology, cosmic inflation is a theory which posits that in the first 10-35 of a second after the Big Bang, the universe underwent a period of rapid, exponential inflation, with it increasing in size by a factor of at least 1026, or "to essentially arbitrarily large universe", i.e. at miraculous rate much faster than the currently measured speed of light.[note 1] It was first proposed by Alan Guth of MIT, in 1981, who declared, in line with tenets of postmodern science, to explore "the question of whether it is in principle possible to ignite inflation in a hypothetical laboratory, thereby creating a new universe". The theory, described by Alexei V. Filippenko as "seductively powerful", tries to account for several objections to the Big Bang model, in order to preserve the illusion that this model explains the origin of the universe. J.Hartnett calls Cosmic Inflation theory an ad hoc assumption rather than specification of a causal mechanism, introduced by Big Bang theorists as a result of three-fold need:
- Due to extreme density of its initial stages, the early Big Bang scenario was in danger of gravitationally driven re-collapse into a singularity.
- The lack of "natural explanation" for the extraordinarily uniform and homogeneous properties of cosmic microwave background radiation (CMBR) indicated by the observational evidence.
- The Big Bang was supposed to produce at early stages so called magnetic monopoles and inflation should disperse them prior to production of elementary particles to allow claims that these magnetic monopoles are too rare to be encountered now.
Problems with the Big Bang model
The Flatness problem
The critical density of the universe is the density at which the universe's rate of expansion will slow down, and eventually reach a rate of zero, as the age of the universe becomes very, very large. Densities above or below this would lead to the universe eventually collapsing back on itself during to gravity, or expanding at an every increasing rate, respectively. Today's best estimates of the universe's density place it staggeringly close to the critical density - the universe is described as being almost "flat", since the shape of the universe's geometry is decided by its density - hence the name of the flatness problem. If the universe's density is extrapolated back until just after the Big Bang, it is found to be exceedingly close to 1 - given that it can take any value, this value leading to a perfectly "flat" universe seems unlikely to have been chosen at random. 
The explanation offered by cosmic inflation is that the period of exponential expansion which occurred essentially "ironed out" any small creases in the early universe, leading to the visible universe's shape being flat.
The Horizon problem
In accordance with the Cosmological principle, the observable universe is seen to be both homogeneous and isotropic on large scales (that is, the "same", no matter where you are, or where you look).  Given the vast size of the observable universe, and the finite age of the universe, there is no reason for the universe to be so "smooth" - there has not been enough time for light to travel between two points at opposite ends of the universe, and so they are not causally connected, and there should be no reason for them to have such similar properties.
Cosmic inflation offers an explanation, in that the universe expanded by such a large amount, over such a small time, so the entire visible universe is in fact a very small portion of the early universe (in causal contact with surrounding points at that time) which was expanded into everything seen today.
The Magnetic Monopole problem
Several physical theories, such as General Relativity and some Grand Unified Theories predict the existence of particles called magnetic monopoles, as well as the magnetic dipoles easily observed in nature. However, no monopoles have ever been observed, and given the success of other aspects of the Standard Model, this was unexpected.
However, if the magnetic monopoles were created before the period of expansion posited by cosmic inflation as is expected, they would have been diluted throughout the universe, since the distance between two neighbouring particles would have been increased by such a huge factor, so there may only be one monopole (if that) present in the entire visible universe.
- ↑ cf. “There are considerable variations in the speed of expansion . It may be much faster than the speed of light as it is supposed to have been in the first zillionth of a second after the Bing Bang according to inflation theory, a now very popular patch up of the original BBC (Big Bang Cosmology), which Pecker refers to as the New Big Bang.“  In the final section of his 1905 paper, Einstein explicitly states that, “velocities greater than that of light have … no possibility of existence.” If proponents of Inflation theory are at the same time adherents of Einstein’s theories, then one may argue that their theory represents a system with no possibility of existence by their own standards or the theory clearly represents a miracle beyond natural laws accepted by them.
- ↑ 1.0 1.1 Alex on the Frontiers of Astronomy 4 Our Universe One of many (September 24, 2013). Retrieved on October 31, 2013. “[06min:00sec]The standard Big Bang theory has no natural explanation for why the energy density of the universe should be exactly this critical value such as that the energy density of the universe divided by the critical value is exactly the unity. It’s an arbitrary thing in a Big Bang -it could have been anything. ... The theory is seductively powerful ... And then universe went through gigantic exponential expansion that took it from a microscopically tiny size-scales to essentially arbitrarily large universe.”
- ↑ 2.0 2.1 2.2 Alex Williams, John Hartnett (2005). Dismantling the Big Bang. Green Forest, AR, USA: Master Books, 121-125, 130-131, 145. ISBN 978-0-89051-437-5.
- ↑ MarcoM. Capria, Aubert Daigneaut et al. (2005). "13. Standard Cosmology and Other Possible Universes", Physics Before and After Einstein. IOS Press. ISBN 1-58603-462-6.
- ↑ A.Einstein (June 30, 1905). On the Electrodynamics of Moving Bodies. Annalen der Physik. 17:891. pp. 23. http://www.fourmilab.ch/etexts/einstein/specrel/specrel.pdf.
- ↑ Faculty Directory: Alan Guth, Victor F. Weisskopf Professor of Physics. Massachusetts Institute of Technology, Department of Physics. Retrieved on 03.03.2013.
- ↑ http://physicsworld.com/cws/article/print/24768
- ↑ http://www.symmetrymagazine.org/cms/?pid=1000045
- ↑ 8.0 8.1 http://www.daviddarling.info/encyclopedia/C/critical_density.html
- ↑ http://csep10.phys.utk.edu/astr162/lect/cosmology/cp.html
- ↑ http://superstringtheory.com/cosmo/cosmo4.html