WHAT IS THE STEADY STATE THEORY??
Blog#67 Wednesday, March 3rd ,2021
The Big Bang theory states that the Universe originated from an incredibly hot and dense state 13.7 billion years ago and has been expanding and cooling ever since. It is now generally accepted by most cosmologists. However, this hasn’t always been the case and for a while the Steady State theory was very popular. This theory was developed in 1948 by Fred Hoyle (1915-2001), Herman Bondi (1919-2005) and Thomas Gold (1920-2004) as an alternative to the Big Bang to explain the origin and expansion of the Universe. At the heart of the Steady State theory is the Perfect Cosmological Principle.
This states that the Universe is infinite in extent, infinitely old and, taken as a whole, it is the same in all directions and at all times in the past and at all times in the future. In other words, the Universe doesn’t evolve or change over time. The theory does acknowledge that change takes place on a smaller scale. If we take a small region of the Universe, such as the neighborhood of the Sun, it does change over time as individual stars burn up their fuel and die, eventually becoming objects such as black dwarfs, neutrons stars and black holes. The Steady State state theory proposes that new stars are continually created all the time at the rate needed to replace the stars which have used up their fuel and have stopped shining.
So, if we take a large enough region of space, and by large we mean tens of millions of light years across, the average amount of light emitted doesn’t change over time. Arguments in favor of the Steady State Hypothesis include the apparent time-scale problem raised by the observed rate of cosmic expansion (aka. the Hubble Constant or the Hubble-Lemaitre law). Based on Hubble’s observations of nearby galaxies, he calculated that the Universe was expanding at a velocity that increased systematically with distance.
However, ongoing observations during the 1950s and 1960s steadily led to a buildup of evidence against the Steady State Hypothesis. These included the discovery of bright radio sources (aka. quasars and radio galaxies) which were discovered in distant galaxies but not those closest to us – indicating that many galaxies became “radio-quiet” over time. By 1961, surveys of radio sources allowed for statistical analyses to be made, which ruled out the possibility that bright radio galaxies were uniformly distributed. Another major argument against the Steady State Hypothesis was the discovery of the Cosmic Microwave Background (CMB) in 1964, which the Big Bang model predicted.
Combined with the absence of a gamma-ray background and pervasive clouds of x-ray emitting gas, the Big Bang model became widely accepted by the 1960s. By the 1990s, observations with the Hubble Space Telescope and other observatories also discovered that cosmic expansion has not been consistent over time. During the last three billion years, in fact, it has been accelerating.
(Saturday, March 6th ,2021)
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