If you believe in Redshifts you have to Believe in the Big Bang

The concept of redshift and the Big Bang theory are inextricably linked. Understanding redshift is fundamental to grasping the evidence supporting the Big Bang. While it's possible to analyze redshift data without explicitly stating "I believe in the Big Bang," the interpretation of that data almost inevitably leads to the same conclusion: an expanding universe originating from a singular, incredibly dense state.

Redshift, in essence, is the stretching of light waves as they travel through space. When we observe light from distant galaxies, we often find that the wavelengths of this light have been shifted towards the red end of the spectrum. 

This shift is analogous to the Doppler effect, where the pitch of a siren changes as it moves away from us. In the case of light, the redshift indicates that the galaxies are moving away from us.

The crucial observation is that the farther away a galaxy is, the greater its redshift. This relationship, known as Hubble's Law, suggests that the universe is expanding uniformly. 

If the universe is expanding, it implies that it was smaller and denser in the past. Extrapolating this expansion backward in time leads to a point where all matter and energy in the universe were concentrated in an extremely hot, dense singularity – the Big Bang.

Skeptics might argue that redshift could be caused by other phenomena, such as light losing energy as it travels through space (tired light theory) or some unknown physical process. However, these alternative explanations have significant drawbacks. For example, the tired light theory fails to explain the observed time dilation of distant supernovae, which is perfectly consistent with an expanding universe.

The argument that redshift necessitates belief in the Big Bang rests on the following points:

• Hubble's Law: The observed linear relationship between redshift and distance strongly suggests a uniform expansion of the universe.

• Cosmic Microwave Background (CMB): The CMB, a remnant of the Big Bang, provides further evidence for a hot, dense early universe. Redshift plays a role in explaining the observed temperature of the CMB, as it has been redshifted to microwave wavelengths due to the expansion of space.

• Abundance of Light Elements: The Big Bang theory predicts the observed abundances of light elements like hydrogen, helium, and lithium. These abundances are consistent with the nucleosynthesis that would have occurred in the early, hot, and dense universe. Redshift calculations are used to refine our understanding of the conditions present during this nucleosynthesis.

• Lack of Viable Alternatives: While alternative explanations for redshift exist, they struggle to explain the full range of observational data as consistently as the Big Bang model.

While it is possible to analyze redshift data and discuss the expanding universe without saying the words “Big Bang”, the conclusions that are drawn from that data are very much in line with the big bang model. To accept that the universe is expanding, with galaxies moving away from each other at speeds proportional to their distance, you are in essence accepting the core tenant of the big bang. The logical conclusion of an expanding universe, extrapolated back in time, is a singular point of origin.

Therefore, while one might technically avoid explicitly stating "I believe in the Big Bang," accepting the evidence for redshift and the expanding universe necessitates accepting the fundamental principles that underpin the Big Bang theory. The redshift of light is a powerful piece of evidence that leads scientists to believe that the universe has expanded from a smaller denser state, which is the core concept of the Big Bang.