A few different theories about the origin of the universe exist today. The Steady State Theory was developed in the late 1940s. This chapter offers an overview of this theory as well as comparing it to the Big Bang theory.
The term 'steady state' means a stable condition that does not change over time or in which change in one direction is continually balanced by change in another. The Steady State Theory of the origin of the universe is also referred to as the infinite universe theory or continuous creation. This theory was proposed by Hermann Bondi, Thomas Gold, and Sir Fred Hoyle. See image 1.
The Steady State Theory states that our universe looks the same from every spot in it and at every time. A steady state universe has no beginning or end. Bondi and Gold suggested that in order to understand the universe we need to observe its distant parts. To interpret these observations we must use the laws of physics. For Bondi and Gold the laws of physics would have to be the same in all parts of the universe and at all times. The Steady State Theory states that although the universe is expanding, it does not change its look over time. For this to work, new matter must be formed to keep the density equal over time.
According to the Big Bang theory, the matter around us was created out of nothing in the beginning. Hoyle tried to solve the problem of creation mathematically. He proposed that the decrease in the density of the universe caused by its expansion is balanced by the continuous creation of matter. The matter condenses into new galaxies that replace receded galaxies. The expansion and creation work against each other and a steady state of energy is maintained.
Helium and hydrogen are the most common elements in the universe. A helium atom is created from a hydrogen atom in the process of nuclear fusion that occurs within stars. The steady state astronomers stated that these large quantities of hydrogen and helium in the universe are created by supernovae. The Big Bang theory suggests that all elements were produced at the start of the universe out of nothing. Now, both theories accept that supernovae play an important role in the formation of heavy elements.
The Steady State Theory began to fade in the 1960s after the discovery of quasars. A quasar is thought to be a luminous galactic core, powered by a super-massive black hole. Quasars are so far away from us that their light has taken several billion years to reach the Earth. So, quasars are objects from the past which indicate that a few billion years ago the structure of the universe was very different from how it is today. See image 2.
The final 'blow' to the Steady State Theory was delivered by radio astronomers Arno Penzias and Robert Wilson. These scientists discovered the cosmic microwave (high frequency radio wave) background which is thought to be leftover radiation from the Big Bang. The Steady State Theory has explained this background radiation as the light from ancient stars which has been absorbed and emitted in all directions by galactic particles. Most astronomers were not convinced by this explanation because the discovered microwave background was very smooth, meaning that it did not come from different small sources. Also, its spectrum is close to that of an ideal black body. In physics a black body is the body that absorbs all electromagnetic radiation. The Steady State Theory is now no longer accepted by most cosmologists. Today the majority of astronomers consider the Big Bang theory to be the best description of the origin of the universe. See image 3.