The relative abundance of hydrogen/helium was well known before the Big Bang theory was formulated so how is predicting that which is already known meaningful? And it didn’t require a particle accelerator to find this out.
And here I was getting ready to write a long response to what could have been summed up in a sentence!
[The relative abundance of hydrogen/helium was well known before the Big Bang theory was formulated so how is predicting that which is already known meaningful? And it didn’t require a particle accelerator to find this out.]
Because inherent in the Big Bang theory is details of the process for the synthesis of elements from simpler subatomic particles. These details not only predict the relative abundance of these elements but they also predict HOW and WHY they are produced. It’s more than just spitting out a number (which was already known) it’s about explaining the process and then using the explanation to make predictions about that which isn’t known and then running experiments to see if those predictions come true.
And they do come true which means the theory is, by definition, both “robust” and “reliable”. Search for “Quantum Electrodynamics” for more info on this.