The Big Bang theory is the most widely accepted explanation for the origin and evolution of the universe based on the available scientific evidence. While it is true that the term "Big Bang" might give the impression of an explosion, the theory does not propose an explosion occurring within a preexisting space. Instead, the Big Bang theory describes the expansion of space itself from an extremely hot, dense, and compact state.
Here are some key points that support the Big Bang theory:
Observational evidence: Astronomers have observed that galaxies are moving away from each other in all directions, indicating an expanding universe. This expansion was inferred from the redshift of light from distant galaxies, known as the Hubble's Law. This observational evidence strongly supports the idea of an early, highly compact state from which the universe expanded.
Cosmic microwave background radiation: The discovery of the cosmic microwave background radiation (CMB) in 1965 provided significant evidence for the Big Bang. The CMB is a faint radiation pervading the entire universe and is considered to be the remnants of the hot, dense state of the early universe. Its discovery and subsequent detailed measurements align with the predictions of the Big Bang theory.
Abundance of light elements: The Big Bang theory successfully explains the observed abundances of light elements, such as hydrogen and helium, in the universe. It predicts the relative amounts of these elements based on the conditions and processes that existed during the early stages of the universe's expansion.
General Relativity: Einstein's theory of General Relativity, which describes the gravitational interactions in the universe, provides a mathematical framework that supports the Big Bang theory. The equations of General Relativity predict an expanding universe and, when applied to the early universe, suggest a singularity—a state of infinite density and temperature—from which the expansion originated.
It is important to note that the Big Bang theory does not attempt to explain the ultimate cause of the universe or what existed before the Big Bang itself. It focuses on understanding the development of the universe from its earliest stages up to the present. Speculations about what may have occurred before the Big Bang fall within the realm of theoretical physics, and current scientific understanding has limitations in addressing such questions.