Our particular universe is governed by the laws of physics and is about 14 billion years old. It began with a singularity that expanded rapidly in what is called the big bang. On earth, atoms formed into proteins, which formed into complex organisms over the course of millions of years. One million years ago, there were at least a dozen species of humans. By 30,000 years ago, only two species of humans still existed as all the others had gone extinct. Today, Homo Sapiens are the only species that remain. H. Sapiens were interesting because they had reached an evolutionary limit. While some animals were the biggest or the fastest, H. Sapiens' brains had developed to the extent that they could not give birth unassisted (due to the large cranium), but were cabable of abstract thought. They created music, religion, and new ways to grow food. Sometime between 2,000 and 3,500 years ago, a human in the Levant plagerized part of a thousand year old Babylonian script on the creation of the world and added a bunch of genealogy to it. He knew nothing of the universe or geology, so he winged it by saying that the earth was flat and the sky was a giant blue dome. Today, we call this the creation story. Some people who don't understand physics still believe it.
That being said, we don't know what started the big bang. Many scientists believe in alternate dimensions beyond our universe. Many scientists believe in parallel universes that may not be governed by the laws of physics. Could they possibly have stumbled into a scientific explanation for hell and heaven? Could the big bang have been started by God?Who knows?