The answer is the big bang witch goes as follows
The Big Bang model is that the universe begun in an extremely dense and hot condition and has expanded. The theory suggests, and measurements show, that the universe is still expanding today.
The Big Bang is a scientific theory about how the universe started, and then made the stars and galaxies we see today.
The universe began as a very hot, small, and dense superforce (the mix of the four fundamental forces), with no stars, atoms, form, or structure (called a "singularity"). Then about 13.8 billion years ago,[1] space expanded very quickly (thus the name "Big Bang"). This started the formation of atoms, which eventually led to the formation of stars and galaxies. It was Georges Lemaître who first noted (in 1927) that an expanding universe could be traced back in time to an originating single point. The universe is still expanding today, and getting colder as well.
As a whole, the universe is growing and the temperature is falling as time passes. Cosmology is the study of how the universe began and its development. Scientists who study cosmology agree that the Big Bang theory matches what they have observed so far. although there are flaws in this theory such as where did the explosion come from and even if u could find a way to explain the creation of the explosion itself there is the tiny fact that u cant create something from nothing however there would be starting material in this theory it wouldn't simply create more and since the theory states that the world will grow infinitely this is impossible but as i said it is a theory and the most accepted at that
