[Physics Class Notes] on Steady-State Theory Pdf for Exam

We all know about the Big Bang theory of how the universe came into existence. The steady-state universe theory is put forward as an alternative to the Big Bang theory. The steady-state theory states that the universe is always expanding, but it maintains the same density. We know that the state of matter depends on how dense its particles are. Thus, if the density of an object remains the same while its size continues to increase, we can say that that object is in a constant or steady state. The same concept when applied to the universe gives us a steady-state hypothesis.

A formal statement for the steady-state theory:

It states that the universe is constantly expanding while retaining a constant average density.

Steady-State Theory Explanation

It can be a bit confusing to understand how the steady-state universe theory could make sense. Let’s break it down here so that it’s simpler to understand.

The universe is filled with various kinds of celestial objects and collections of these celestial objects. It has stars, planets, asteroids, moons, meteors, and so many other such celestial bodies. The proponent of steady-state theory in simpler terms is that as the universe grows or expands, the number of celestial bodies also proportionally increases.

To put it differently, if the size of the universe is increasing but the number of celestial bodies is not, there will be a decrease in the density. Now, alongside the increasing size of the universe, the number of planets and stars, and other bodies are also increasing, and thus, the density remains more or less the same.

Steady-State Theory Evidence, or Lack Thereof

The steady-state theory proponents were Sir Fred Hoyle, Sir Hermann Bondi, and Thomas Gold. It was taken forward by Sir Hoyle after the propounding of the theory. The model used since the 1950s for any observations, which is the Cosmic Microwave Background, does not count much for evidence which is mostly because it comes from the Big bang theory, to which the steady-state theory was propounded as an alternative.

[]

Features of Steady State Universe Theory

This theory assumes that all the galaxies existing in the universe are moving slowly away from one another. Because of what the theory states, that as the universe expands, the galaxies and other celestial bodies in the universe also proportionately expand, the steady-state universe theory also assumes that new matter is constantly being created in the universe. The propounders of the theory also put forth the speed derived at which new matter is created, which is at the rate of 1 atom of hydrogen per 6 cubic kilometers of space per year, which is an incredibly minuscule amount. Another one of the features of steady-state theory is that it considers the universe to be stable and steady, as the name suggests.

The Drawbacks of the Steady State Theory

Unfortunately, there is more evidence against this theory than there are steady-state theory facts and tangible evidence. While there are definite predictions that could be tested via observation, those observations were the reason why it did not gain much clout in cosmology. The radio observations made went far into the universe, and returned with information from billions of light-years ago with evidence of a changing universe, which is pretty much the opposite of what the theory propounds. The cosmic microwave background also could not provide much evidence for this theory. These are the two main reasons that the big bang theory has been looked at as the origin of the universe and the steady-state theory put aside.