Big Bang Theory
The Big Bang theory had its beginnings in the 1920s when a Belgian priest named Georges Lemaitre theorized that the universe began from a single primordial atom. This idea afterwards received major boosts by Edwin Hubble’s observations that galaxies are speeding away from us in all directions.
The theory suggests that about 10 billion years ago all the matter in the universe was contained in a hot, dense ball of radiation and subatomic particles. The temperature of this ball of matter was incredibly high – billions and billions of degrees. An explosion took place and the matter expanded. As it expanded it cooled and electrons, protons and neutrons formed. On further expansion and further cooling small gaseous atoms like hydrogen and helium formed, then larger ones. Since being cooled by expanding, to its present state it still continues to expand.
The Big Bang is the leading theory that almost all astrophysicists believe explains the origin of the universe. This is because all observations so far made support the Big Bang theory; there are four main lines of evidence that are most-often used.
The first observation: The expansion of the universe. The universe is expanding now, so in the past it must have been smaller. If it were smaller in the past, then there probably was a time when it was infinitesimally small.
The second observation: The evidence of the Cosmic Microwave Background Radiation (CMB) that was discovered in 1965 by Arno Penzias and Robert Wilson from Bell Labs. They were working with a microwave receiver, but were getting noise from every direction they pointed the receiver. It was coming from all over the sky at what seemed to be exactly the same frequency; this was the first evidence for the CMB.
The third observation: The great amount of different elements of the universe. The theory predicts that certain amounts of hydrogen, helium, and other elements should be made. Observations have shown almost exactly the amounts that are predicted.
The fourth observation: It is the only one that completely lays down a framework for the final expansion of the universe as we observe it today.
The theory suggests that about 10 billion years ago all the matter in the universe was contained in a hot, dense ball of radiation and subatomic particles. The temperature of this ball of matter was incredibly high – billions and billions of degrees. An explosion took place and the matter expanded. As it expanded it cooled and electrons, protons and neutrons formed. On further expansion and further cooling small gaseous atoms like hydrogen and helium formed, then larger ones. Since being cooled by expanding, to its present state it still continues to expand.
The Big Bang is the leading theory that almost all astrophysicists believe explains the origin of the universe. This is because all observations so far made support the Big Bang theory; there are four main lines of evidence that are most-often used.
The first observation: The expansion of the universe. The universe is expanding now, so in the past it must have been smaller. If it were smaller in the past, then there probably was a time when it was infinitesimally small.
The second observation: The evidence of the Cosmic Microwave Background Radiation (CMB) that was discovered in 1965 by Arno Penzias and Robert Wilson from Bell Labs. They were working with a microwave receiver, but were getting noise from every direction they pointed the receiver. It was coming from all over the sky at what seemed to be exactly the same frequency; this was the first evidence for the CMB.
The third observation: The great amount of different elements of the universe. The theory predicts that certain amounts of hydrogen, helium, and other elements should be made. Observations have shown almost exactly the amounts that are predicted.
The fourth observation: It is the only one that completely lays down a framework for the final expansion of the universe as we observe it today.
Steady State Theory
The Steady State theory is a cosmological theory for the origin of the universe that suggests the universe has always existed and did not have a moment of creation. The Steady State theory was inspired by a 1940s movie entitled Dead of Night. After seeing this movie in 1946, Thomas Gold, Hermann Bondi, and Fred Hoyle wondered if the universe might not be constructed the same way. The discussion that followed eventually led to the Steady State theory.
This theory suggests that the universe has always existed. We see the universe now as it was in the past and will be in the future. This means that the universe would be infinitely old; it would have no birth date and would never end. The Steady State theory suggests that new matter is created everywhere in the universe, this matter forms galaxies which slowly move away from each other. This means that some galaxies in a particular area of space are younger than others. It is believed that new stars and galaxies would form to fill any empty space left behind when old stars and galaxies moved apart.
The Steady State theory is a general theory of only some astronomers. They believe that the universe has no beginning or end but remains much the same throughout time. This is based on a set of four beliefs generally known as the perfect cosmological principle.
The first belief: The physical laws are universal. Any science experiment if performed under identical conditions will have the same result anywhere in the universe because physical laws are the same everywhere in the universe.
The second belief: On an acceptably large scale the universe is the same. There is large scale structure in the universe, such as clusters of galaxies; so, it is assumed that the universe is the same only on scales large enough for even the largest structures to average out.
The third belief: It is assumed that the universe is isotropic, meaning that there is no preferred direction in the universe.
The fourth belief: It is assumed that over an acceptably long time, the universe looks basically the same at all times.
This theory suggests that the universe has always existed. We see the universe now as it was in the past and will be in the future. This means that the universe would be infinitely old; it would have no birth date and would never end. The Steady State theory suggests that new matter is created everywhere in the universe, this matter forms galaxies which slowly move away from each other. This means that some galaxies in a particular area of space are younger than others. It is believed that new stars and galaxies would form to fill any empty space left behind when old stars and galaxies moved apart.
The Steady State theory is a general theory of only some astronomers. They believe that the universe has no beginning or end but remains much the same throughout time. This is based on a set of four beliefs generally known as the perfect cosmological principle.
The first belief: The physical laws are universal. Any science experiment if performed under identical conditions will have the same result anywhere in the universe because physical laws are the same everywhere in the universe.
The second belief: On an acceptably large scale the universe is the same. There is large scale structure in the universe, such as clusters of galaxies; so, it is assumed that the universe is the same only on scales large enough for even the largest structures to average out.
The third belief: It is assumed that the universe is isotropic, meaning that there is no preferred direction in the universe.
The fourth belief: It is assumed that over an acceptably long time, the universe looks basically the same at all times.