Seeking answers to questions involves imagining the answer then seeing how well it fits the question. Seeking flaws in our answers can be more valuable than the answer itself. This becomes particularly true when one's answer serves as a pillar for answering future questions.
How many disciplines engage people in finding out what is wrong with their answers? The physics discipline could particularly benefit from ongoing self-scrutiny of its foundational pillars. Today we consider the Big Bang.
Einstein with his general relativity presented an elegant and powerful mathematical tool for analyzing gravitational relationships. His analysis relied on the concept of a spacetime continuum to extend Isaac Newton's laws of universal gravitation. Time is treated as a fourth dimension by converting it into distance using the speed of light. Time as we all know, or think we know, flows on mysteriously and continuously.
In 1922 Alexander Friedmann, building on Einstein's and de Sitter's field equations, produced equations for the ultimate contraction or expansion of the universe. In 1927 Georges Lemaître proposed an expanding model of the universe to explain the observed redshifts of spiral nebulae. In 1929 Edwin Hubble provided an observational foundation for Lemaître's theory. Hence, was born the Big Bang model of the universe.
In 1964 the Cosmic Microwave Background was discovered. This was believed to confirm expansion of the universe. In 1990 the COBE satellite showed the CMB spectrum matches a 2.725K black-body. Dark matter was needed to match the small anisotropies in the CMB. Mainstream alternatives to the Big Bang model became very rare after this time.
The concept of Dark Matter evolved after the matter in the universe was estimated by Lord Kelvin in 1884. Originally, it meant unseen matter. Now, it means an unknown type of matter. Spiral galaxy rotation curves helped promote the concept of Dark Matter. It was needed to account for the stronger than expected gravity at distant regions. Mordehai Milgrom's MOND gravity provided an alternative, but that seems to garner less favor.
In 1998 measurements of supernovae indicated the expansion of the universe is accelerating. Hence, was born Dark Energy.
In April of 2019 (this year) Hubble measurements confirmed that more distant regions of the universe were expanding more slowly than nearby regions. An explanation of this has not yet been formulated.
Do you see a common thread here? The Big Bang model evolved during the first half century. The Big Bang model required numerous patches to keep it working during the last half century. It borders on heresy to say that the Big Bang model is wrong. This limits scrutiny of the model's foundations.
This example of the Big Bang illustrates why we need an organized, sanctioned search for flaws in the underpinnings of physics. Only by actively looking for our flaws do we progress toward a solution.
Perhaps we should start at the beginning and look at our lack of understanding of time (i.e. spacetime)and question the original application of general relativity to the distant universe.