Steady State Hypothesis vs Big Bang Theory: The Scientific Debate That Redefined Our Understanding of the Universe

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What do we mean by "hypothesis” and “theory”?

  • Why we need to understand it first, because today's topic is "Steady state hypothesis" and "Big Bang expending University theory." 
  • So, when we are using the terminology "theory" with "Big Bang", we will be looking at how, after the imperial scientific evidence, the Big Bang has transformed itself from a hypothesis into a theory. So, let's start Steady State Hypothesis -&- Big Bang – Expanding Universe Theory 😊



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Steady State Hypothesis 


  • It is better to have an understanding of a particular topic or other subject from your surrounding environment. So, to understand the "steady state concept hypothesis", I think the political doctrine "conservatism" would be an ideal example to understand.

Doctrine of "Conservatism"
  • This political doctrine emphasises the preservation of -
  1. traditional institutions, 
  2. customs, 
  3. values, and 
  4. social order. 

  • In its extreme traditional form, it strongly resists change and seeks to maintain the existing social and political structure, because the belief is that -
  1. stability, 
  2. tradition, 
  3. authority, and 
  4. gradual evolution is preferable to rapid change, revolution, or radical reform.

But- 

  • Extreme Conservatism represents a preference for a closed and stable social order in which major social, political, and economic transformations are viewed as undesirable. 
  • However, history repeatedly demonstrates that change is an inherent law of nature and an indispensable feature of human civilisation.

  • Whenever legitimate demands for reform and transformation have been persistently suppressed, as witnessed in "Nepal's democratic movements" against autocratic rule, societies have often experienced revolutions, uprisings, and periods of upheaval. In such circumstances, the pace of change becomes rapid, disruptive, and sometimes destructive because gradual adaptation was denied for too long.
  • In essence, -
  1. History teaches us that societies survive not by rejecting change altogether (But Steady State, rejecting change in density ), 
  2. But by managing and adapting to change (But Steady State did not adapt itself to fluctuation and transformation in the universe) in a constructive and timely manner. 
  • The suppression of necessary reforms may delay transformation, but it rarely prevents it; instead, it often magnifies the intensity of change when it eventually arrives. In the case of "the Steady state hypothesis",  this change came and hypothesisi collpase by coming years of the 1960s.



"Steady State hypothesis”

  • In the year 1948, the Steady State Hypothesis was formally proposed by:
  1. Fred Hoyle
  2. Hermann Bondi
  3. Thomas Gold

  • At the baseline theory accepted Hubble's expansion but argued that:

  1. The universe has no beginning.
  2. The universe has no end.
  3. New matter is continuously created to maintain a constant average density.

Key Points

  • "The Perfect Cosmological Principle" considers the universe to be homogeneous and isotropic on a large scale. As a result, the universe appears the same everywhere and at all times. From a conceptual point of view, this can be regarded as a conservative outlook, similar to the doctrine of conservatism, which prefers continuity and stability.
  • The hypothesis denies the existence of a starting point or birth of the universe and instead considers it eternal. 
  • As a consequence, the hypothesis is compelled to state that the universe has always existed and will continue to exist forever.
  • The hypothesis mainly talks about a mean density, meaning that throughout the universe, an average density is maintained. 
  • Another ironic feature of the hypothesis is that it recognises the universe as expanding.
  • Now, when we combine these two ideas—an expanding universe and a constant average density—it implies that new matter must be continuously created to maintain the mean density. 
  • The hypothesis recognised this as one of its fundamental principles, and for this reason, it is also known as the "Continuous Creation Hypothesis."
  • A question naturally arises regarding the previously created matter. Due to continuous expansion, after a certain period of time, much of this matter becomes invisible to the observer. What happens beyond that point is not clearly answered by the hypothesis. 
  • Yet, the theory maintains the position that no additional matter significantly alters the overall character of the universe.
  • One inference that can be drawn from this hypothesis is that, because the universe has to maintain its mean density, it will continue to expand and expand and expand.
  • Despite all these assumptions and exceptions, the universe is still considered to appear static and unchanged. 
  • In this sense, it resembles ot our discussed political outlook that is not reluctant to acknowledge transformation and prefers continuity over change.
  • The following image, through a flowchart, graphically explains this hypothesis well-

  • Therefore, the Steady State Hypothesis can be regarded as a fundamentally closed view of the universe. As scientific observations increasingly pointed towards an evolving universe, the hypothesis found it difficult to sustain itself and consequently had strong reasons to be rejected by the scientific community by the 1960s.




Comparative Analysis

The "Big Bang Theory"

  • In the Big Bang analysis, we are not going to discuss the timeline as it has been discussed on various platforms with its chronology. So, very briefly, through the following image I am providing you with the Big Bang Theory chronology. 
The Chronology -&- Milestone moments of Big-Bang

  • Based on the above chronology of this Big Bang, we need to note 04 milestone events-

  1. Due to the intense energy, the matter got separated into electron, proton, neutron and neutrino.
  2. The expansion continued, and with this expansion, it maintained an inverse relationship with temperature, so gradually, temperature dropped to 4226 degrees Centigrade.
  3. The moment the temperature reached 4226 degrees centigrade, it created a stable/favourable condition for an electron, proton or neutron to collide, which led to the formation of the first "hydrogen" atom.
  4. Now, as a consequence, "hydrogen" leads to the formation of "helium" and the existence of a star, because we know in our star/Sun, hydrogen continuously converts into helium through nuclear fusion. 

  • Our main focus over here shall be on how this hypothesis converts itself into a theory. So we will discuss those evidence which are having the scientific empirical values in support of the Big Bang Theory.

Empirical EVIDENCE in support of Big Bang-



As shown in the image, the five pieces of evidence are provided in this file. Most importantly, we are going to discuss here which are -
  1. Edwin Hubble Red Shift
  2. CMBR, and 
  3. NASA's WMAP


Edwin Hubble Red Shift

  • During the early twentieth century, astronomers observed that the spectral lines of many galaxies were shifted toward the red end.
  • Later, from 1929 to 1929 Edwin Hubble systematically studied these observations and found that most galaxies exhibit red shift.

  • Hubble discovered that the farther a galaxy is, the greater its red shift. Hubble expressed a relationship known as "Hubble's Law", which states that distant galaxies recede faster than nearby ones.
  • According to Hubble, red shift is the phenomenon in which light from a celestial object shifts toward the red end of the spectrum because distance is increasing and red colour maintains a longer wavelength.
  • As the object recedes, its light waves become stretched, increasing their wavelength and appearing red in colour.
  • This increase in wavelength causes the light to shift toward the red region, known as red shift.
Conclusion
  • Red shift provided the first direct observational evidence that the universe is expanding.
  • An expanding universe implies that galaxies were closer together in the past. 



Cosmic Microwave Background Radiation (CMBR): A Major Evidence of the Big Bang Theory

Accidental Discovery of CMBR

  • Many important scientific discoveries have occurred by chance.
  • One such discovery was the "Cosmic Microwave Background Radiation (CMBR)."
  • In 1965, Arno Penzias and Robert Wilson were conducting "radio-astronomical observations" using a microwave antenna.
  • They repeatedly detected a faint and persistent background noise coming from every direction in space.
  • After eliminating all possible sources of interference, they realized that the signal was cosmic in origin.
  • This led to the accidental discovery of CMBR, providing powerful evidence for the Big Bang Theory.


CMBR?

  • Cosmic Microwave Background Radiation (CMBR) is the faint electromagnetic radiation present throughout the universe.
  • It is often referred to as the "afterglow" or "relic radiation" of the Big Bang.
  • It is highly important to note that CMBR had already been predicted by the Big Bang Theory before its discovery.

CMBR Origin-

  • It is estimated that the early universe was extremely hot, dense, and opaque.
  • About 380,000 years after the Big Bang, the universe cooled sufficiently, up to 4226 degrees centigrade, for electrons and protons to combine and form neutral atoms.
  • This period is known as the Recombination Era.
  • Before recombination, free electrons continuously scatter photons, preventing light from traveling freely.
  • After neutral atoms formed, photons decoupled from matter and began moving freely through space, which is observed today as CMBR.

Important Characteristics

  • Present throughout the universe almost uniformly in all directions, indicating that the early universe was nearly homogeneous and isotropic.
  • The present temperature approximately 2.725 Kelvin (-270.4°C).
  • Due to the continuous expansion of the universe, the original high-energy radiation has been stretched into the microwave region of the electromagnetic spectrum.
  • CMBR exhibits an almost perfect blackbody spectrum, exactly as predicted by the Big Bang model.
  • Tiny temperature fluctuations (anisotropies) represent the initial density variations that later evolved into galaxies, galaxy clusters, and large-scale cosmic structures.

Conclusion

  • CMBR, the relic microwave radiation, left over from the Big Bang. Its existence, uniform distribution, blackbody nature, and temperature closely match theoretical predictions. Therefore, regarded as one of the strongest and most direct observational evidences for the Big Bang Theory and the expansion of the universe.


WMAP (Wilkinson Microwave Anisotropy Probe) as Evidence for the Big Bang Theory

Background-

  • After the discovery of the CMBR, scientists had a wish to study it in greater detail to understand the origin and evolution of the universe.
  • To achieve this objective, "NASA" launched the Wilkinson Microwave Anisotropy Probe (WMAP) on 30 June 2001.
  • Named after American cosmologist "David Todd Wilkinson."
  • It was designed to map the Cosmic Microwave Background Radiation (CMBR) across the entire sky with unprecedented accuracy.

Objective?

  • To measure tiny temperature variations present in the CMBR.
  • These variations contain valuable information about the-
  1. origin, 
  2. age, 
  3. composition, and 
  4. evolution of the universe.

Discovery?

  • WMAP produced the most detailed full-sky map of the Cosmic Microwave Background Radiation, which we have discussed in a previous topic, available at the time.
  • It detected extremely small temperature fluctuations in the CMBR, known as "anisotropies." which concludes the presence of slight density differences in the early universe and are considered a zone of creation of new material in the universe, and thats how lated evolced into- 
  1. galaxies, 
  2. galaxy clusters, and 
  3. large-scale cosmic structures.

Conclusion

  • It estimated the age of the universe to be approximately 13.7 billion years, and confirmed that the universe originated from a hot, dense, and nearly uniform state, as predicted by the Big Bang Theory.
  • The universe is nearly flat in its geometry, and has been expanding and cooling since the Big Bang.
  • The universe originated from a hot and dense state.
  • It measured the tiny temperature variations within the CMBR, and that's how WMAP acted as a powerful observational tool that verified and strengthened the evidence provided by the CMBR.


Summing up from "Hypothesis" to "Theory"

  • Thus, the cumulative evidence provided by -
  1. Red Shift, 
  2. CMBR, and 
  3. WMAP firmly established that the universe is expanding. The remarkable agreement between these observations and the predictions of the Big Bang model demonstrated that the Big Bang was not merely a speculative hypothesis but a real cosmic event, ultimately transforming the Big Bang Hypothesis into the scientifically accepted Big Bang Theory.



















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