What is the Big Bang theory?

TL;DR:

The Big Bang is a theory about how the universe physically expanded from an initial state of high density and temperature. It is not a theory of the ultimate creation of the universe.

The Bible doesn't really say anything directly about the Big Bang theory. The theory is a mathematical model attempting to describe how the universe expanded from an initial state of extremely high density and temperature. The Big Bang model was first suggested by combining the observed expansion of the universe with Einstein’s General Relativity. While several independent lines of evidence support the Big Bang model, it is still being developed and tested. It undergoes modifications when new observations don't fit the model. Alternatives to the Big Bang include the eternal universe and the multiverse, neither of which has biblical support nor scientific support. The Big Bang theory might explain how the universe physically changed after the instant of a “beginning,” but says nothing about how or why that beginning occurred. The actual creation event of the universe remains beyond the probing of cosmologists. However, the Bible is clear about how the universe started and Who created it.

from the old testament

The Old Testament does not say anything specific regarding the Big Bang theory.
The Bible tells us that God created the heavens and the earth (Genesis 1:1).

from the new testament

Colossians 2:8 warns believers against following worldly philosophies based on human tradition. While much of the Big Bang theory has scientific merit,
Non-believers often make speculative claims that the Big Bang demonstrates that there is no “need” for God. Such claims lack evidence and logical support. The Big Bang model itself says nothing about biology or life.
By faith we understand that the universe was created by the word of God, so that what is seen was not made out of things that are visible (Hebrews 11:3). This verse affirms that God did not use preexisting material to create the universe. Since the text is written for all generations it does not provide scientific detail as to how creation occurred.

implications for today

The Big Bang describes a model of the universe expanding from an initial state of extremely high density and temperature. This singularity expanded rapidly, and as it did, it cooled and formed subatomic particles, atoms, and eventually the stars and galaxies we see today. Interestingly, both the Big Bang theory and the Bible (Genesis 1:3, 14) suggest that photons (light) existed before stars (the sun). The theory is supported by a range of observational evidence, including the expansion of the universe, cosmic microwave background radiation and the abundance of light elements. The Big Bang implies that the universe began to expand around 13.7 billion years ago.

The Big Bang theory is based on Einstein’s General Relativity (theory of gravity), which accurately describes the behavior of matter and energy on large scales. General Relativity is well established, but it does not say how things started. In 1927 the Catholic Priest and astronomer Georges Lemaitre first applied Einstein’s work to the expanding universe, implying that it could be traced back to a single point of origin. Prior to this most scientists believed the universe was infinite and eternal. There was significant resistance to the idea that the universe had a beginning because of the religious implications. Today, based on the evidence, most cosmologists accept the idea that the universe had a beginning, although opinions vary widely on the initial cause, which Genesis 1:1 tells us was God.

The Big Bang theory is not complete and has several untested predictions and missing pieces. An unsettling claim is that 95% of the energy in the universe is in an unknown form, called dark energy and dark matter, which have never been observed. The Big Bang theory is still being developed.

This link answers the question if the Big Bang theory is compatible with the Bible.

https://www.compellingtruth.org/big-bang-theory-Bible.html

understand

The Big Bang theory explains that the universe expanded from an initial state of extremely high density and temperature.
The Big Bang theory is not complete and does not explain how the universe was created, though it is often linked to debates over the age of the earth.
The Big Bang theory describes how the universe evolved, not how it began, leaving the initial cause unanswered, which is where the Bible points to God as the Creator.

reflect

How does understanding the Big Bang theory as a description of the universe's expansion rather than its creation affect your view of the relationship between science and faith?
How does knowing that the Bible attributes the universe's creation to God influence your perception of scientific theories like the Big Bang?
How can you reconcile the scientific aspects of the Big Bang theory with the biblical account of creation?

engage

Many people take issue with the Big Bang theory due to its implications. Some believers see it as an erasure of God from our understanding of nature. This is because modern atheism uses the Big Bang Theory to claim naturalistic origins—but when the theory was first suggested, atheists strongly resisted it because it so obviously suggested a supernatural origin. Additionally, the theory's incomplete nature and unresolved aspects, like dark matter and dark energy, contribute to skepticism and debate. However, when discussing the theory, we can remind people of what is known versus what is not. The Big Bang theory has not been proven, but it does reveal people’s interest in the universe God created. The Big Bang theory can potentially be compatible with Christian beliefs if understood as describing the mechanism of the universe's expansion rather than its ultimate origin. While the theory does not address the theological aspects of creation, it does not necessarily conflict with the belief in God as the Creator of the universe. It does, however, conflict with a young earth model.
How might the Big Bang theory’s focus on the universe’s expansion shape or challenge our understanding of God’s role in creation?
Considering that the Big Bang theory does not address the ultimate cause of the universe, how can Christians use this theory to discuss and explore theological questions about creation and God?