"Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.In an older and closely related meaning, "science" also refers to a body of knowledge itself, of the type that can be rationally explained and reliably applied. A practitioner of science is known as a scientist."
You can't test the big bang. No one was there to see it happen. You can't recreate it. It a guess. That's all it is. Scientists will NEVER be able to prove the big bang, so it is just a belief. They have to put as much faith in the big bang as Christian have to to believe in theological creation.
Also for that very same reason they can't disprove the hollow earth theory. There is no way that scientists can truly know what lies in the center of the earth , because they can't go there. They can't test the core of the earth because they can't get any samples of what the core is like.
500 years ago the world was flat and you could heal people by leeching them dry.
In short: all science is is best guess.its all conjecture.