No-one was around during the big bang, no-one has ever seen a star’s lifecycle from birth to clataclysmic death, and we can’t put these things in the lab to test them, so where do scientists get the audacity to claim that these things happened and are happening?
A few weeks ago, I wrote a column in the Zululand Fever where I put the discipline of science within the confines of testability. I said that when one makes a claim on how nature works, then we can test it and prove it wrong or right and I claimed that anything outside this “testability” perimeter is therefore “unscientific” and “supernatural”.
A friend of mine then asked me about the Big Bang theory and how it is accepted as the origin of the universe, being an event that occurred only once, if it indeed did occur. He said, “We can’t conduct an experiment in the lab where we see the big bang again.” He also listed other things rendered “unscientific” by my testability assertion, such as multiverses and black holes (those massive stars that are so hefty that not even light can escape their gravity).
Well, the universe acts in mysterious ways but we can find generalisations from observing how it works, like noticing how objects fall the same way every time you drop them. Scientists then formulate mathematical explanations that need to satisfy these generalisations and once they are up to par, we test them on nature. And if they pass these tests, we call them "laws of nature".
Now, each of these remains "true" until a more efficient explanation comes along. In other words, we use Ockham's razor, i.e. we cut the rubbish.
Edwin Hubble in 1929 observed that galaxies seem to be moving away from each other, as if the space between them were expanding. This changed the static view of the universe accepted at the time. Around the same time, Georges Lemaitre theorised that if the universe is expanding then it means if you extrapolate backwards it must have existed in one point in space, thus the big bang theory was born (though it was not called that at the time).
It became popular among the scientific fraternity because it was the simplest explanation for the origins of an expanding universe amidst other explanations that were much less elegant.
But we still needed to ‘prove’ the theory by finding evidence for it in nature. Obviously we couldn't use the same physical phenomenon that gave birth to it to prove it so we turned to mathematics and the mathematical results resulted testable (observable) physical phenomena.
One of these was the cosmic microwave background (CMB) which heralded indirect evidence for the big bang as it was found completely independently in 1964. At the moment there are scientists looking to disprove the big bang theory by finding phenomenon not predicted by or against the theory and until that happens, we accept it as the origin of the universe, and all major theories go through this baptism of fire all the time.
“But we can't test it in the lab,” he said. Well, astrophysicists almost never get to touch or experiment on their specimens, but they can construct good enough theories to explain phenomena from little more than star shine and use those to predict other phenomena whichwhen found to be true are then accepted as true until Ockham comes in.
What of multiverses and black holes? Well, the idea of multi-verses theorises that there are other universes existing outside of ours and this crazy idea came from the observation that some subatomic particles (which operate on a completely different set of laws called Quantum Theory) can exist in two places at once and even disappear here and appear somewhere else.
At the moment, the idea of multiple universes in existence are the best explanation for this and other funny behaviour and it has given birth the mathematical model of the universe called String Theory (or M-theory) which is yet to be proven but is our best bet that can be tested as we get better sophisticated scientific instrumentation.
As for black holes, they were predicted by Albert Einstein in his theory of General Relativity and later found in nature through the powerful gravity they exert on other stars, the x-ray radiation emitted when they devour hapless stars and plumes of gas in space.
Sometimes you just have to observe and deduce and test those deductions by observing somewhere else in nature.