The Big Bang is a scientific theory. In scientific terminology, a theory is a well-substantiated and comprehensive explanation of a phenomenon based on empirical evidence and supported by multiple lines of research. The Big Bang theory is the prevailing scientific explanation for the origin and evolution of the universe.
According to the Big Bang theory, the universe began as an extremely hot and dense point around 13.8 billion years ago. It then expanded rapidly, leading to the formation of matter, galaxies, and the structure we observe today. The theory is supported by various lines of evidence, such as the observation of the cosmic microwave background radiation, the abundance of light elements, the redshift of distant galaxies, and the large-scale structure of the universe.
It's important to note that in scientific terms, a hypothesis is a proposed explanation or prediction that requires further testing and evidence to become a theory. The Big Bang theory has gone through extensive testing and has accumulated substantial empirical support, making it one of the most widely accepted scientific theories in cosmology.