Now, think about what would be required to do today to tear down one of our leading scientific theories. It’s not as complicated as you might imagine: all it would take is a single observation of any phenomenon that contradicted the Big Bang’s predictions. Within the context of General Relativity, if you could find a theoretical consequence of the Big Bang that didn’t match up with our observations, we’d truly be in store for a revolution.
But here’s the important part: that won’t mean that everything about the Big Bang is wrong. General Relativity didn’t mean everything about Newtonian gravity was wrong; it simply exposed the limit of where and how Newtonian gravity was successful. It will still be accurate to describe the Universe as having originated from a hot, dense, expanding state; it will still be accurate to describe our observable Universe as being many billions of years old (but not infinite in age); it will still be accurate to talk about the first stars and galaxies, the first neutral atoms, and the first stable atomic nuclei.
Whatever comes along to replace it — whatever supersedes our present best theory (and this applies to all scientific realms) — its first order of business is to reproduce all the successes of that theory. The steady state or static Universe theories that seek to supplant the Big Bang? They can’t even do that much. Same thing for the electric Universe/plasma cosmology group; same thing for the tired light adherents; same thing for the quantized quasar redshift camp; same thing for the topological defect/cosmic string aficionados.