Cosmic expansion

Cosmic expansion refers to the constant separation, or expansion, of all space in the universe over time. Albert Einstein suggested the potential cosmic expansion of the universe in his theory of relativity, but the first studies that have essentially proven cosmic expansion were in 1929 by a man named Edwin Hubble. From his observations, he formulated Hubble's Law. "The apparent recession velocity of a galaxy v is proportional to its distance d from the observer: v=H0d, where the constant of proportionality H0 is known as the Hubble constant."

The subject of Universal expansion can face much confusion and objections. Many people are mislead by what this expansion really is. If all space and matter in the universe expanded simultaneously, not only would the empty space in between objects expand, but the objects would expand, as well. Galaxies would be further apart, but the galaxies and all matter that makes them up would also be greater in size. If this was true, expanding the space between planets by double the distance would also double the size of the planets and to the observer it would look as if nothing happened. If the observer expands as well as any form of a measuring device, it is hard to say what expansion really means. According to Hubble's Law, the space in between objects is constantly expanding, but the objects themselves, like planets, people, stars, are essentially maintaining their size of matter and shape as a constant.

Effects on Distance
In cosmology, a unit of distance is defined as light multiplied by time. Edwin Hubble, the founder of Hubble's Law and the man who proved that the universe is expanding, created a unit of distance known as the Hubble length. One unit of Hubble length is c/H0. This measurement is equal to about fourteen billion light years.

As the universe expands, the space between objects recedes and becomes further away in distance. This is the most clear and evident effect caused by cosmic expansion. Although the space between objects expands, the objects, themselves, maintain the same size. There are different analogies to help explain this concept. One example is the raisin bread analogy. If there was a ball of raisin bread dough that consisted of the bread dough with raisins dispersed throughout the dough, the bread would be put in the oven and begin to expand. As the bread expands, the raisins become farther apart from each other. The farther the raisins are from each other, the faster they will recede from each other. This essentially applies to cosmic expansion in how the more distant galaxies are from each other, the faster they recede from one another.

Effects on Light
While the universe continues to expand, not only distance is affected. Light is also greatly affected by the constant expansion of the universe. During this expansion, light waves travel through our universe and, due to the expansion, will get stretched out and create longer wavelengths. When Edwin Hubble was doing his research on galaxies, he realized their light was being redshifted. Due to this, the galaxy clusters are moving away from each other.

Inflation
Cosmic inflation is essentially a type of cosmic expansion, although the term refers to a specific event at the beginning of time. Inflation is the extreme accelerated expansion of the Universe.

Cosmic inflation is said to be an event that is considered a period of time that took place immediately after the Big Bang event. Cosmic Inflation occurred 10-36 second after the Big Bang expansion. Then it settled into the present expansion we see today. In the cosmic inflation period, a so-called vacuum energy spread across the whole Universe. This vacuum energy later created all the matter in the universe.

Credit for the development of this theory belongs to Alan Guth (See Also: Borde-Guth-Vilenkin singularity theorem), Andrei Linde, Paul Steinhardt, and Andy Albrecht. Prior to their formulated theory, much evidence from previous studies were suggesting this event. Vesto Melvin Slipher used this information to research galaxy movement according to their spectral shift in the early 1920's. Shortly after, in 1922, Alexander Friedmann became the first man to propose that not only did the universe initially expand rapidly, but it is currently expanding. Edwin Hubble, creator of the Hubble's Law, used these previous studies to determine that galaxies tend to be traveling away from us. Hubble used the galaxies' spectral shifts to prove his studies. In his studies, he discovered that the universe is expanding. He noticed that the more distant the galaxy is from us, the faster it seems to be receding. The only apparent solution to this problem is that the space in the universe is in constant expansion.

According to the theory of cosmic expansion, the universe began as a quantum fluctuation that was 1020 times smaller than the size of the proton. Within that rapid amount of time, the universe managed to increase in size by about 1026 times its original size. The speed of this inflation towers over the speed of light, and the force of this inflation was great enough to overcome the force of gravity. Within seconds, the Universe had a diameter of about four inches.

Inflation can be viewed as a hypothesis created to save errors in the big bang theory. Prior to the formulation of the inflation theory, problems began to arise relating to heat. One of the most known and argued problem is known as the horizon problem, which is a light-travel problem. For the heat to have been evenly equalized throughout the Universe, more than ten times the amount of time from the Big Bang would have been necessary. The theory of cosmic inflation was formulated to try and rescue the big bang theory.