Question

according to this theory the universe is still expanding what theory is this?

Answer 1

The theory you are referring to is the **Big Bang Theory**, which posits that the universe began from an extremely hot and dense state and has been expanding ever since. Observations, notably the redshift of distant galaxies and the cosmic microwave background radiation, support the idea that the universe is still expanding today. This expansion is also described by Einstein's General Theory of Relativity and is further analyzed through the framework of cosmological models, such as the Lambda Cold Dark Matter (ΛCDM) model, which includes dark energy as a driving force behind the accelerated expansion of the universe.