The life of the cosmos is a subject of heated debate and fervent speculation for scientists, astronomers, cosmologists and astrophysicists. How did it begin? How did it evolve? How did it assume its current shape and behavior? How will it end? Presently, the most likely theory to appeal to for answers is what’s known as the Inflationary Universe theory. According to it, the early universe expanded at an exponential rate for the first few fractions of a second following the Big Bang.
This theory was put forward in 1981 by cosmologists in order to solve various problems in their own field.
PROBLEMS WITH INFLATION THEORY
One such problem is called the horizon problem. If we follow this theory’s logic, but assume that the Universe is not expanding, and that two photons simultaneously depart from the same point, one aimed at the Earth’s North Pole, and the other aimed at the Earth’s South Pole. The logic goes that, since these two particles could not exchange any information from the time released, the time required to send information from one photon to the other would be twice the age of the cosmos.
These photons in are causally disconnected; they cannot penetrate one another’s horizon.
But this can’t be, since we have already observed photons approaching from opposite directions that must have somehow communicated, since the cosmic microwave background radiation is nearly homogeneous, i.e. unchanging across different sectors of the night sky.
HOW DO WE SOLVE THIS PROBLEM?
We can solve this problem by assuming that the universe expanded exponentially at its earliest beginnings, shortly after the Big Bang. Before this happened, the whole of the cosmos was in causal contact, and at equilibrium with a common, homogeneous temperature. This means that sectors of the universe that are widely separated today were once extremely close together, which explains why photons from these disparate and distant regions have the same temperatures.
AN ANALOGY
To visualize cosmic inflation, imagine the inflation of a balloon. One person at any point on the balloon may think they are at the center of expansion, since each and every neighboring point appears to move farther away as the surface of the balloon extends from the interior pressure.
For more on the universe’s beginnings, cosmic inflation and quantum fluctuations, check out Stephen Hawking’s Centre for Theoretical Cosmology.
