It’s a term that creationists and other science-doubters like to abuse. When we try to explain to them how the Big Bang and evolution can explain the origins and development of life in the universe, their rebuttal is that they are “just theories”.
Certain members of the general public seem to think that scientific ideas are just vaguely formed ideas that can be moulded to form an anti-religious narrative, and deny the existence of the divine. But what we mean in science when we use the term “theory” is extremely different to what is meant its ordinary usage. “It’s just a theory” is a complaint that should never be uttered with regard to theories like the Big Bang and evolution.
Not all Theories are Tested…
While the most well known theories in science have a huge quantity of experimental evidence backing them up, it is not the case that all scientific theories have been experimentally verified and accepted as fact. This doesn’t mean that some theories are just vague ideas though. Even if a theory has not been thoroughly tested it will still have a very detailed and fleshed out exposition.
The examples to which I want to draw you to come from my own area of interest – theoretical physics. String theory and Supersymmetry theory are two theories of theoretical physics that have not been experimentally tested and established as fact, but we still call them theories. This is because these theories have been extensively researched and explored mathematically.
Take one of the key textbooks in the field “Superstring Theory” by Green, Schwarz and Witten. This is an introductory textbook for graduate students comprised of two volumes each about 500 pages long. These textbooks are hundreds of pages of advanced mathematics and physics that set up the foundations of the theory – let alone all the research that has been going on since the 1980s when this textbook was written!
So even if scientific theories are yet to be experimentally tested, they are very detailed, intricate and specific. They are not just vague, wild ideas.
But Lots of them Have Been
If we’re talking about theories like evolution and the Big Bang however, then you’re talking about theories that have both an enormously detailed theoretical foundation and also an enormous amount of experimental evidence in their favour.
Take the Big Bang for instance: red-shift, the CMB and the relative abundances of elements in the universe are all decisive validations of the theory. What many Big Bang doubters try to suggest however is that these three key pieces of evidence are the only major tests of the theory, and that really the Big Bang theory is on the verge of collapse.
But this is just nonsense. There are thousands and thousands of peer reviewed scientific papers in cosmology which take the Big Bang theory for granted and use it to correctly predict phenomena that we observe in our universe. In the 20th century there was an apparent crisis for the Big Bang theory when the estimated age of the universe was about 3 to 8 billion years younger than the estimates of ages of the oldest stars in the Milky Way. Further research and more precise measurements produced better estimates for these ages and found that there was no longer any conflict between the ages.
One of the best ways to convey just how solid these theories are is by quoting the biologist J.Haldane, who said that finding just a single rabbit fossil in the Precambrian would destroy his acceptance of evolution. It’s the same with the Big Bang theory. Just one astronomical observation that would seemingly contradict the Big Bang theory would be enough to cast serious doubt over it. Both in biology and in cosmology however, thousands and thousands of fossils and galaxies are investigated every day and no “Precambrian rabbit” has been found. These scientific theories are as good as fact.