The Inflationary Theory was developed in the 1970s to help explain several mysteries that werent addressed in the Big Bang Theory.  It was also used to say why scientists havent been able to find magnetic monopoles (single north or south poles that are not connected to another pole).  The theory was also used to explain why the universe seems so homogeneous or uniform.

In this paragraph you will learn how fast the expansion of the universe took place.  Read more to find out this amazing theory. This period of expansion started 1 × 10-35 sec after the big bang and lasted only 1 × 10-32 sec (1 × 10-35 and 1 × 10-32 are extremely small numbersa decimal point followed by thirty-four zeroes and then a 1, or thirty one zeroes and then a 1, respectively).  During that very brief interval the universe expanded to be 1 × 1050 times its previous size (1 × 1050 is a very large numbera 1 followed by 50 zeroes).  This expansion then was well done within the first second of time in the universe. Then the universes expansion became more like it is in todays present rate.

In the Inflationary Theory, it is thought that the universe began in a minuscule area of space.  The region was so compact that all parts could be in contact with each other.  This allowed the universe to become very homogeneous.  After the expansion started and is happening the universe became more spread out.  This gives us the almost homogeneous universe we see today.  On a small scale though it isnt very homogeneous, because in our galaxy things are seemingly put together in lumps.  But on a larger scale, clusters of galaxies are spread out much more evenly.

The Inflationary Theory also explains how our universe could be ever expanding or would contract and get smaller again.  If the universe is dense enough, the force of gravity may eventually overcome the universes expansion and start pulling matter in the universe back together. Cosmologists are still trying to find out how dense the universe is. The estimations fall very close to the dividing value between a universe that expands forever (an open universe) and a universe that eventually contracts (a closed universe). The inflationary period in the theory would have expanded the universe just fast enough for it to reach the size that led to the estimated density of todays universe. (MSN Encarta, source. Thank You!)

The Inflationary Theory also tries to explain the existence of magnetic monopoles, which other which other physical and cosmological theories predict.  But the theory also explains that the universe expanded greatly in just a second, so that relatively few magnetic monopoles were spread far apart.  Cosmologists use the Inflationary Theory to explain how there might only be one magnetic monopole in the observable universe. 

The best evidence for the inflationary universethe homogeneity of the universe, the mass density of the universe, and the absence of magnetic monopoleswas also the justification for the theory.  (Thank you MSN Encarta!)   But for this reason, some scientists have criticized the theory for not being testable.  One reason for this is that we still dont know the universes density!  Because of some disagreement is being argued that the Inflationary Theory shouldnt be a theory. 

The current version of the inflationary theory predicts that the density of the universe is very close to the value that divides the two possibilities for the future of the universe: expanding forever or eventually ending expansion and beginning to shrink. If scientists collect definitive evidence that the universe is open, or will expand forever, the inflationary theory would be proved false. (MSN Encarta!)

The Inflationary Theory was created at MIT (Massachusetts Institute of Technology) by Alan Guth in the 1970s.