But I want to convince you that science is not merely a body of facts. It is not merely something engaged in during the working week by people who studied to become scientists. Perhaps most importantly for this audience, science is not a weapon of mass propaganda wielded by unbelieving apostates intent on robbing your children of a place in God's kingdom. Science is not your enemy. Science is simply a method or process by which we can understand the world and reality. You probably use this method all the time without realising it.
Science as a method
Science at its core is really just a method, or set of tools, for figuring out how reality works, what probably happened in the past, and for predicting what might happen in the future. But it is much more than just a useful tool. It can provide answers to deep questions, some of which defy our intuitions and challenge our pre-conceived notions of what reality is and how it works. We know the method works because it leads to real-world outcomes, consistent with the detailed explanations that underlie the predictions. These explanations add to our understanding of the world, and that understanding can be tested via prediction and experiment. Science is a process, and it produces explanations and understanding. It is also self-correcting, and designed to eliminate biases and errors.
Science is not new
Science has been with us since at least the time of the ancient Greeks, and likely long before that. Its methods have been refined over time, and in more modern times it was greatly advanced by the work of Nicolaus Copernicus and Galileo Galilei in the 16th century and many other great scientists in the centuries since then. It is important to note that Galileo was not the first to produce a working model of planetary motion. The previous understanding of the solar system prior to Copernicus placed the Earth in the center with the planets following predictable but sometimes complex paths across the sky. The key advantage of Copernicus's model was that it provided a much simpler explanation of the solar system while making the same accurate predictions.
We now know that even the heliocentric model is not the whole story. For just as the Earth orbits the Sun, so the Sun orbits the centre of the Milky Way galaxy, and the galaxy is also itself not stationary. Heliocentrism is not "wrong" per se, but rather it has been superseded by far more complete theories, including General Relativity. What I find far more interesting than the facts themselves, is by what methods and discoveries we came to know them.
How do we know what is real?
By plotting the locations of planets in the night sky, using a telescope, early scientists were able to come up with models which could then be used to make predictions. Those predictions could be tested against future observations to determine whether the models accurately represented reality. If not, the models could be updated and new predictions and measurements made. But this is not the whole story. As discussed above, earlier geocentric models were already able to account for the motion of planets, albeit in a more complicated way. So another principle of science is that of explanatory efficiency, otherwise known as Occam's Razor. This is more of a guide than a rule, but the basic idea is that explanations requiring fewer assumptions are to be preferred. In practice this is not always easy to do, but at least in the case of cosmology, the heliocentric model of the solar system was clearly much simpler, and eventually provided much greater explanatory power.
We can use this example to demonstrate further aspects of the scientific method. Suppose there was an alternative model that made all of the same predictions as the Copernican model, but also predicted that the planets might spontaneously and suddenly reverse their motion at some unspecified time in the future. How would we decide between the two models? Both made the same predictions, except that certain predictions from the alternative model are unable to be tested, even in principle. What we would ideally be looking for is some way to test both models in such a way that we could rule out one while confirming the other. That is, we need to find a test that could be performed, where the predictions of each model differ from each other, and then we could compare each prediction with the actual result and thereby rule out one or both models.
If such a test or measurement could not be performed, even in principle, then according to Occam's Razor, we would be better to revert to the simpler of the two models, at least until such time as some experiment or measurement disagreed with that model. And this is exactly how scientists proceed. The ability to make testable predictions is called falsifiability, and is one of the foundations of modern scientific theories and models today. Any hypothesis that cannot be tested, even in principle, is not taken seriously, since it cannot lead to any greater understanding or explanation of reality. Examples include miracle claims, claims of an afterlife, and of course creationism.
There is an additional point that is worth stating for the above example. The Copernican model also features a plausible explanation consistent with the predictions it makes, whereas the alternative model has no such explanation for why the planets should suddenly reverse their path through space. Any explanation offered for this as-yet-unobserved reversal would likely also be far more complicated than the Copernican model's explanation.
Meanwhile, those who argue in favour of divine creationism, whether for the origin of life or the origin of the universe, cannot offer a sufficient explanation for their claim. This is because the "explanation" that everything we see was designed by God could just as well be made for any configuration of any possible universe, and thus it does not explain anything at all. Further, creationism makes no predictions, testable or otherwise, for much the same reason. It is akin to claiming that the world arose by sheer magic. There is no possible configuration of the world for which the very same claim could not be made.
What can science tell us about reality?
According to atomic theory, all matter is made of particles. Some particles are "unstable" (or radioactive), meaning that they will eventually decay into other particles. The rate at which such particles decay can be measured, and we thereby know the decay rates of many different particle isotopes. Each isotope yields a specific decay rate which can be measured and predicted to a high degree of accuracy. We cannot predict when any single radioactive atom will decay, but given a large enough sample we can predict with very high accuracy how long it will take for roughly half of them to decay. This is known as the "half life" of a radioactive isotope.
Why is this important? Well, because we know that all living matter contains both the radioactive isotope carbon-14, as well as normal carbon, carbon-12. The ratio of carbon-14 to carbon-12 in the air and all living things remains very near constant, as the carbon-14, although decaying at a known rate, is replaced by new carbon-14 atoms over time. This is true for living organisms. When an organism dies however, it stops taking in new carbon. Over time, the remaining carbon-14 then decays, again at the known rate. So by measuring the ratio of these isotopes in an organism that has died some time ago, we can calculate backwards and determine with relatively high precision how long ago that organism died.
This is not only true of Carbon-14 but also of various other combinations of isotopes. In some cases, measurements can be made using several isotope combinations, which each have different half-lives, thereby vastly increasing the accuracy of the measurement.
This method has been tested many, many times on organisms of known age, as you can read for yourself in this paper. There are many others. By repeatedly confirming the results via experiments with samples of known age, we gain increased confidence that the methodology and explanations behind the model are likewise accurate. Thus, scientists are able to quite confidently show that, for example, the Dead Sea Scrolls were likely produced sometime around the latter couple of centuries BC. The very same methods also tell us the ages of organisms going back tens of thousands of years.
Carbon-14 has a relatively short half-life compared to other isotopes, which means that it cannot be used for organisms that died more than about 50,000 years ago. For such organisms we need to rely on other methods, such as dating the rocks and rock layers that the organisms were buried in, and this is typically done using a combination of radiometric dating and other geological techniques. This works for trees and plants just as well as for animals, fish and even coral. Much information can be understood about Earth's history simply by observing the sedimentary rock layers laid down over long periods of time (complete with periods of erosion between deposits).
Choose your sources
It may be tempting for believers such as Christadelphians to insist that science can yield truth but only when it agrees with their previously held beliefs. Some therefore insist that only those scientists whose findings agree with their favourite doctrines are to be accepted, and all others summarily rejected as heretics or as being misguided. There are several problems with this approach.
Firstly, by whose judgement was this distinction made? Without proper training in the relevant fields, how were you able to determine which scientists are closer to truth and which ones are mistaken?
Secondly, if by your reckoning, the number of scientists who were mistaken (despite collectively many lifetimes of dedicated research) vastly outnumber those who discovered the truth, would it not be even more improbable that you somehow managed to discover this truth, without even basic training?
Thirdly, and most importantly, one of the key ways in which science proceeds is through publications in reputable journals, each subjected to rigorous peer review. This is a process whereby scientists do their best to point out any errors in the work of their peers and colleagues, with the goal of ensuring the highest quality standards in what is published. Every paper is scrutinised by others in the relevant fields, and sloppy work is likely to be rejected. Many experiments are replicated and the replicated results are also published following the same peer-review process. The process is not perfect, but it is very good, and far better than any known alternative. On what grounds therefore would we as laypersons be justified in rejecting all of this peer-reviewed research in favour of following a handful of scientists most of whose work has yet to pass peer-review?
It is of course possible, though extremely improbable, that the vast majority of scientists are wrong about biology, palaeontology, cosmology, astrophysics, geology and a range of other scientific fields of study, but perhaps those of us who possess very little expertise in any of these fields beyond a secondary-school level, might be wise to consider that the majority of scientists in these fields just might know something we don't. But we don't have to guess. We can read about their discoveries and understanding for ourselves.
The beauty of science is that it doesn't just teach us how nature works, it documents how it reached its conclusions. Don't just look at the facts of science and pick and choose which ones you agree with. Dig deeper. Ask how they know, and keep reading until you understand it yourself. If you do not understand it, then you are not in a place to form a belief on it. Better to withhold judgement and admit you don't know, than to foolishly commit to a belief without understanding.
How do you know that?
So next time you hear or read of a claim about reality, whether from a scientific source or a religious one, don't be afraid to ask, "How do you know that?", and then be prepared to follow that question as far as necessary to reach an answer that is grounded in evidence. Remember, the difference with science is that it can explain not only how something works, but also how it knows what it knows. It will also often describe further ways to test it, and even ways to potentially prove it false. Science is also upfront and honest about what it doesn't (yet) know. But what science does not know, it is likely that no one knows it, for without science they lack the methods by which to test it and discover it.
If on the other hand someone tells you that if you follow what they say a magical being will grant you everlasting life after you die, ask them, "How do you know that?" and then ask how you might test it. If it cannot be tested, then how did they know it is true? Isn't it rather more likely they don't know it? It is far easier to profess a false confidence than to prove that what one says is true. We should ask for proof and evidence, lest we become gullible and give up our entire life to follow another's fable. Those who value their own life, and truth, will endeavour to be more discerning about how they spend the first and seek the second.
Science is our best tool for discovering charlatans and guarding against being fooled. It is also our best window into the inner workings of reality and the fascinating wonders of the universe we live in. There is much we don't know, but there is also humility in that admission. The future is exciting, as more discoveries lie in wait to be made. There is nothing more human than to seek to know more about ourselves, and about our universe and our place within it. Only a fool would insist they already know it all.