Inflation model” and “Inflation theory” redirect here. Following the inflationary period, the Universe continues to expand, but at a less rapid rate. It developed further in the the cosmic landscape pdf 1980s.
This was quickly interpreted as meaning galaxies were receding from earth. If earth is not in some special, privileged, central position in the universe, then it would mean all galaxies are moving apart, and the further away, the faster they are moving away. Many other observations agree, and also lead to the same conclusion. However for many years it was not clear why or how the universe might be expanding, or what it might signify.
It was very quickly realized that such an expansion would resolve many other long-standing problems. Inflation theory largely resolves these problems as well, thus making a universe like ours much more likely in the context of Big Bang theory. 2012 – 2013 and is still being researched. So it is not seen as problematic that a field responsible for cosmic inflation and the metric expansion of space has not yet been discovered.
Universe cannot communicate with Earth yet. These parts of the Universe are outside our current cosmological horizon. In the standard hot big bang model, without inflation, the cosmological horizon moves out, bringing new regions into view. This presents a mystery: how did these new regions know what temperature and curvature they were supposed to have? A space with a cosmological constant is qualitatively different: instead of moving outward, the cosmological horizon stays put. The spatial slices are expanding very fast to cover huge volumes.
Things are constantly moving beyond the cosmological horizon, which is a fixed distance away, and everything becomes homogeneous. As the inflationary field slowly relaxes to the vacuum, the cosmological constant goes to zero and space begins to expand normally. The new regions that come into view during the normal expansion phase are exactly the same regions that were pushed out of the horizon during inflation, and so they are at nearly the same temperature and curvature, because they come from the same originally small patch of space. The theory of inflation thus explains why the temperatures and curvatures of different regions are so nearly equal.
It also predicts that the total curvature of a space-slice at constant global time is zero. More strikingly, inflation allows physicists to calculate the minute differences in temperature of different regions from quantum fluctuations during the inflationary era, and many of these quantitative predictions have been confirmed. This means that any inhomogeneities are smoothed out, just as any bumps or matter on the surface of a black hole horizon are swallowed and disappear. The “no-hair” theorem works essentially because the cosmological horizon is no different from a black-hole horizon, except for philosophical disagreements about what is on the other side. During inflation, the energy density in the inflaton field is roughly constant. However, the energy density in everything else, including inhomogeneities, curvature, anisotropies, exotic particles, and standard-model particles is falling, and through sufficient inflation these all become negligible. This is necessary to ensure that the Universe appears flat, homogeneous and isotropic at the largest observable scales.
This relatively low temperature is maintained during the inflationary phase. It was very quickly realised that such an expansion would resolve many other long-standing problems. Inflation attempts to resolve these problems by providing a dynamical mechanism that drives the Universe to this special state, thus making a universe like ours much more likely in the context of the Big Bang theory. For example, molecules in a canister of gas are distributed homogeneously and isotropically because they are in thermal equilibrium: gas throughout the canister has had enough time to interact to dissipate inhomogeneities and anisotropies. The situation is quite different in the big bang model without inflation, because gravitational expansion does not give the early universe enough time to equilibrate.