1

The Big Bang Theory: A Complete Cosmological Model?

Rationale

This report seeks to investigate the claim that “The Big Bang Theory is a complete model of
the universe.” Multiple aspects of this claim could be investigated.

The Big Bang Theory (BBT) is composed of numerous predictions surrounding the universe’s
origin and transformation. As the BBT is an integral basis in understanding the cosmos
(Uzan, 2016), any of these predictions is deserving of investigation.

Moreover, the claim presents the BBT as a “complete model”. This signifies that the BBT is
more accurate at explaining astronomical observations than alternative cosmological
models, e.g., the Steady State Theory (SST).

It has been long debated as to which model is the most ‘complete’. Hence, researchers have
collected a plethora of evidence to scrutinise the two most prominent models of the
universe: the BBT and the SST (Britannica, 2022). In particular, their investigation into the
spread of cosmological bodies and phenomena within the universe, e.g., quasars and Type
Ia supernovae, have tended to favour the predictions of the BBT over the STT (Hurley,
2015). Their results largely suggest the spread of cosmological matter to be uneven
(Kellermann, 2014) — a matter that aligns with the BBT but not the STT.

To further investigate such evidence, the following research question is posed:

Does the BBT propose more accurate predictions than the SST in relation to explaining the
distribution of celestial bodies (quasars) and cosmological phenomena (Type Ia supernovae)
within the universe?

Contrasting Predictions of the BBT and the SST

The BBT and the SST offers contrasting predictions regarding the distribution of celestial
matter within the universe. On one hand, the BBT predicts that the universe is

WANG T. Brisbane State High School PPY101D

 2

heterogenous: the distribution of certain cosmological matter and phenomena varies within
the cosmos (Bertschinger, 2000). The SST, conversely, proposes that the universe is
homogenous: the distribution of cosmological matter remains uniform within the cosmos
(Liddle, 2015).

The disparity between these two models has resulted in further investigation concerning the
distribution of celestial bodies and phenomena. This report focuses on two particular
aspects: quasars, exceptionally luminous and distant astronomical objects (Peterson, 2022);
and Type Ia supernovae, runaway explosions of white dwarfs (Augustyn, 2023).

This report analyses redshift z as a measure for distance. A redshift z of 1 ≈ 1.37710 light
years.

Distribution of Quasars

A Russian-German Spectrum-Roentgen-Gamma (SRG) mission in 2019 launched the

extended Roentgen Survey with an Imaging Telescope Array (eROSITA) into orbit (Predehl, et
al., 2021). Within its first operating year, eROSITA has observed over 11, 000 quasars, and its
findings, plotted on a Hubble diagram, is displayed below (Lusso, 2020).

WANG T. Brisbane State High School PPY101D

 3

Figure 1: Hubble diagram of eROSITA quasars (approximately 11, 000 yellow points),
displayed with redshift z against luminosity (distance modulus) (Lusso, 2020).

As evident in Figure 1, the number of quasars greatly increases at a distance of z ≈ 0.2, and a
rapid decrease at a distance of z ≈ 1.25 follows. This indicates that the distribution of
quasars within the universe is inconsistent. For instance, there are significantly more
quasars at a distance of 0.5 ≤ z < 1.5 than at a distance of 1.5 ≤ z < 2.5.

Thus, the fluctuating relationship between the number of quasars and redshift supports the
predictions of the BBT: the spread of celestial bodies varies across the universe. Such an
inconsistent distribution is likely accredited to the nature of quasars. Quasars require
extensive time to form (Simonetti, n.d.); thus, the rarity of these objects within the early
universe, i.e., the most remote parts of the cosmos (z > 2), is expected. Conversely, as the
universe ages (z < 2), quasars become increasingly more common, which is reflected within
Figure 1. Hence, the graph also invalidates the predictions of the SST: the distribution of
quasars within the universe is not consistent.

Figure 1 supports the BBT and opposes the SST. The former model, consequently, proposes
a more accurate prediction at explaining the uneven distribution of quasars within the
universe.

Distribution of Type Ia Supernovae

As of late, Type Ia supernovae has been studied by three independent research bodies: the
Sloan Digital Sky Survey-II (SDSS-II); the Supernova Legacy Survey (SNLS); and the High-Z
Supernova Search Team (HST) (Kessler, et al., 2009; Pritchet, et al., 2004; Riess, 1998). Their
combined data, plotted on a Hubble diagram, is presented below (Nielson, et al., 2016).

WANG T. Brisbane State High School PPY101D

 4

Figure 2: Hubble diagram of Type Ia supernovae, displayed with redshift z against luminosity
(distance modulus) (Neilson, et al., 2016).

It is evident from Figure 2 that as distance (redshift z) increases, the number of Type Ia
supernovae decreases. Beginning at z = 0.2, the quantity of this cosmological phenomenon
steadily declines until the graph’s conclusion (z ≈ 1.3). This indicates that the spread of Type
Ia supernovae within the universe is inconsistent. For example, there are significantly more
Type Ia supernovae at a distance of 0.8 ≤ z < 1.0 (approximately 60 in total) than at 1.0 ≤ z <
1.2 (approximately 10 in total).

This fluctuating relationship between the number of Type Ia supernovae and redshift, as
suggested by Figure 2, supports the predictions proposed by the BBT: the spread of
cosmological phenomena varies across the universe. This uneven distribution is attributable
to the nature of Type Ia supernovae formation. This particular cosmological phenomenon
necessitates the presence of a white dwarf (National Aeronautics and Space Administration,
2022), a celestial body found more commonly at closer distances within the universe.
Hence, it is expected that Type Ia supernovae would be more frequent at a distance of z <
1.0 and rarer at a distance of z > 1.0, a matter reflected within Figure 2. As such, the graph

WANG T. Brisbane State High School PPY101D

 5

also invalidates the predictions of the SST: the distribution of Type Ia supernovae is not
uniform.

Thus, Figure 2 uniquely supports the claims of the BBT and therefore suggests that the
former is more accurate than the SST at explaining the inconsistent cosmological
distribution of Type Ia supernovae.

Conclusion

The distribution of quasars and Type Ia supernovae was examined and found to be uneven
within the universe. In both figures, the number of celestial bodies and cosmological
phenomena decreased as distance (redshift) increased, indicating an uneven distribution of
quasars and Type Ia supernovae. As such findings uniquely aligned to the predictions of the
BBT but not the SST, the BBT proposes more accurate predictions than the SST in regard to
explaining the distribution of quasars and Type Ia supernovae within the universe.
Consequently, the claim that “The BBT is a complete model of the universe” is supported.

Evaluation

The first source is deemed to be of high credibility. The author, Lusso E., is an astrophysics
specialist at the University of Durham, has written over 50 articles (Durham University,
2023), and affiliated to the Arcetri Astrophysical Observatory — a globally-recognised
cosmological institution (Righini, 1967). However, as measuring extremely distant
astronomical objects are prone to error, this reduces the credibility of the data, harming the
accuracy of identified trends. Nonetheless, while the measurements may contain
inaccuracies, this does not reduce the overall confidence of the results: refining the data
further does not affect the conclusion.

The second source, written by Nielsen, et al. is moderately credible. This report was
approved by the Danish National Research Foundation — an internationally-recognised
astronomical institution (Danish Agency for Science Technology and Innovation, 2013), and
thus increases the source’s credibility. However, the data presented within this source is not

WANG T. Brisbane State High School PPY101D

 6

recent. Namely, the source utilises data from the HST, a cosmological project that concluded
over two decades ago (Riess, 1998). Hence, the results may be outdated and unreliable.
Overall, this suggests the source to be of moderate credibility.

To further the report’s integrity, corroborating sources may be found to mitigate the
inaccuracies found within the first source. Furthermore, to mediate the issue of outdated
information, the collection of more recent sources may be necessary to ensure the data’s
relevance.

Word Count: 1184

WANG T. Brisbane State High School PPY101D

 7

References

Augustyn, A. (2023). Type I supernovae. https://www.britannica.com/supernova/Type-I-

supernovae

Bertschinger, E. (2000). Cosmological Perturbation Theory and Structure Formation.

https://arxiv.org/pdf/astro-ph/0101009.pdf

Britannica, T. Editors of Encyclopaedia. (2002, March 29). steady-state theory.

https://www.britannica.com/science/steady-state-theory

Danish National Research Foundation. (2013). Evaluation of The Danish National Research
Foundation. Danish Agency for Science, Technology and Innovation.

Durham University. (2023). Dr Elizabeth Lusso. https://www.durham.ac.uk/staff/elisabeta-

lusso/

Hurley, S. (2015, July 25). The Steady State Theory.

https://explainingscience.org/2015/07/25/the-steady-state-theory/

Kellermann, K., I. (2014). The Discovery of Quasars and its Aftermath. Journal of
Astronomical History and Heritage. 17(3), 267-282. https://arxiv.org/pdf/1304.3627.pdf

Kessler, R., et al. (2009, August 22). First-Year Sloan Digital Sky Survey-II (SDSS-II)
Supernovae Results: Hubble Diagram and Cosmological Parameters.
https://arxiv.org/pdf/0908.4274.pdf

Liddle, A. (2015). An Introduction to Modern Cosmology. John Wiley & Sons, Ltd.

Lusso, E. (2020). Cosmology with quasars: predictions for eROSITA from a quasar Hubble
diagram. https://arxiv.org/pdf/2002.02464.pdf

WANG T. Brisbane State High School PPY101D

 8

National Aeronautics and Space Administration. (2022). Type Ia Supernova.

https://exoplanets.nasa.gov/resources/2172/type-ia/supernova/

Nielson, J., et al. (2016). Marginal evidence for cosmic acceleration from Type Ia
supernovae. Sci Rep, 6, 1-8. https://doi.org/10.1038/srep35596

Peterson, B. (2023, February 18). quasars. Encyclopaedia Britannica.

https://www.britannica.com/science/quasar

Predehl, P., et al. (2021). The eROSITA X-ray telescope on SRG. First science highlights from
SRG/eROSITA, 647, 1-16. https://doi.org/10.1051/0004-6361/202039313

Pritchet, C. J. (2004, June 9). SNLS – the Supernova Legacy Survey.

https://arxiv.org/pdf/astro-ph/0406242.pdf

Riess, A., et al. (1998, July 1). Results from the High-Z Supernova Search Team.
https://arxiv.org/pdf/astro-ph/9807008.pdf

Righini, G. (1967). The Arcetri Astrophysical Observatory. Solar Physics, 1(3-4), 494-497.
https://adsabs.harvard.edu/full/1967SoPh....1..494R

Simonetti, J. (n.d.). Frequently Asked Questions about Quasars.

https://www1.phys.vt.edu/~jhs/faq/quasars.html

Uzan, J. (2015). The big-bang theory: construction, evolution and status. Séminaire Poincaré,
1-69. https://arxiv.org/pdf/1606.06112.pdf

WANG T. Brisbane State High School PPY101D