I've been stumbling upon posts expressing various kinds of doubts against science on the Internet recently. Either something isn't proved enough, or scientific theories are too abstract, or they are even absurd. All these posts seem to have one thing in common - a fundamental misunderstanding regarding the way science works, or the way it should work. Because of this, I decided to attempt to explain the issue here - what science does, what it doesn't do, and why. Enjoy!
Getting to know the world
We - people - are surrounded by a certain reality. Since times immemorial some people have been noticing that there are some patterns to this reality, that it seems to follow some rules. Some of them got interested enough by this that they wanted to know more. They wanted to understand what the surrounding world actually is and how it works.
And here is where the problems start. The only tool the ancient people had that could help them tackle the problem of uncovering the rules of the world, was their intuition. And that intuition, which is a pretty good evolutionary adaptation to the environment our ancestors lived in, tends to fail spectacularly when applied to problems that weren't a part of that environment. The riddle you can try to solve here serves as a good illustration - I recommend having a go before reading the rest of the article, because it will become much less interesting afterwards.
Noticing that intuition can be deceiving and finding an effective way of counteracting this deception took the humanity a very long time. The result is the scientific method.
What is the scientific method?
The formal definition can be found on Wikipedia, but to put it shortly - it is a set of methods of studying the world that aims to obtain results that are as objective as possible. There are two main approaches to studying the world and we will start with describing these approaches.
Theory and experiment
Let us start with a bit about the experiments, as they are more intuitive.
Simply put, the experimental study of reality consists of gathering data by checking the reality's "answers" to some conditions "posed" to it. The conditions might be "posed" by an observer (eg. in a laboratory), or they can exist naturally (like in astronomical observations, where we don't control the celestial objects at all). We study what happens under what conditions and document it thoroughly, and we get to know some part of the reality this way.
A simple example: our study of reality could consist of checking what happens when we throw some objects in the air. We threw a ball - it fell. We threw a rock - it fell. We threw a fork - it fell. Now we have some data about the reality.
But the experiments themselves are not everything. Studying the reality only by experimenting resembles learning a subject at school by memorizing the textbook - we can answer some questions afterwards, but can we really say that we understand the subject? In order to bring our understanding of reality to the next level, we construct theories.
Theories are systems enabling predicting the reality's behavior under some circumstances. They are tools that give answers to questions like "if the conditions are so and so, what will happen?". Theories give structure to experimental data and enable drawing conclusions beyond just that which has been directly studied experimentally.
In our example, a simple theory could be "objects thrown in the air fall back down". The experimental data has shown that when we threw a ball, a rock or a fork, they fell, which made us attempt to formulate such a theory. If somebody asks us afterwards "and what happens if I throw a pen?", we can answer: "according to our theory, it will fall". We haven't studied this case experimentally yet, but we can reason about it based on our theory.
This begs the question: how do we know that our conclusion from the theory will be correct? That if we perform an experiment we haven't tried before, the result will be what the theory predicts? The answer is: we can't possibly know that! And this is the crux of many misunderstandings.
Verification or falsification?
Can we test our theory in any way? Can we make sure that objects thrown in the air, in fact, always fall? Can we ever be sure that this is how reality works?
Unfortunately, we cannot. No matter how many different objects we throw and observe falling, another one can always do something else. Of course, the more objects we try to throw, the more certain we will get that the theory is correct, as long as the results agree with it. However, our certainty can never reach 100%.
No scientific theory can be completely verified. Every scientific theory can be falsified, though. What is more - falsifiability is often considered a criterion a theory must satisfy to even be considered scientific.
In our example it is enough that a single object thrown in the air doesn't fall, and we will know that our theory can't be a correct description of reality. It is falsifiable, then. Can we falsify it in practice?
Well, it would be enough that someone would hand us a balloon filled with helium to throw, or that we would try to perform our experiments with throwing objects in a falling elevator, for example. In both cases the objects won't fall, falsifying our simple theory.
Does it mean, then, that our theory is useless and should be scrapped? No! It is still correct in some domain. We just need to specify the conditions for its applicability, eg. "objects heavier than air thrown by an observer standing on the ground fall" (of course, in order to come up with a reasonable set of conditions, not having any prior knowledge, we would have to perform tens, hunders, thousands of experiments first). This way we can obtain a theory fitting all experimental results known to us.
Is it already the final theory? And what have I said earlier about complete verification? Someone could still hand us a balloon filled with helium in a vacuum chamber - and suddenly it will turn out that this theory has holes, too. We could again identify the conditions that made it incorrect and amend it further, though.
Sources of theories
In our example, we formulated our theory after performing a few experiments. We gathered some data about reality, noticed a pattern, proposed a general rule. Are theories always created this way?
Not necessarily. If someone, for example, started with an idea, that material objects tend to find themselves on the ground, they could create the same theory. Someone else could simply dream the idea for this theory. In both cases the final result is the same sentence we phrased after our initial observations: objects thrown in the air fall". Are these two theories somehow worse because of where they come from? No! The only thing that decides the value of a theory is how well it predicts the experimental results, not how it came to be. If we have a system that can predict the numbers in a lottery, we will be just as rich if we derived it from the Bible, as if we derived it from detailed observations of previous lottery drawings.
Building theories on ideas or thought experiments instead of on experimental results is actually a common approach in physics. Of course, such theories have to be confronted with experimental results all the same - as I mentioned before, it's how well the predictions match the experiments that decides the value of a theory, and this can only be checked by actually performing experiments. Nevertheless, theories that are based on a single specific idea, or a few of them, and predicting results well at the same time, are considered particularly aesthetic (Einstein's theory of relativity is a great example here). Most theoretical physicists dream of finding a single idea that would allow them to derive a theory correctly predicting every possible experimental result.
What theories say about reality
It is worth making a note at this point about how far we can go in drawing conclusions about reality from a theory.
Imagine that someone postulated an idea that is saying something about reality itself, eg. "the Universe started with the Big Bang". Having such an idea, we can try figuring out various consequences it would have for the actual shape of reality, eg. that space should be constantly expanding, or that there should exist a microwave background radiation, etc. In actual science, both ideas and their consequences are usually expressed in mathematical language, for the sake of maximal precision.
Some of the consequences derived this way will be propositions that can be directly, experimentally tested. It will be possible to check if reality really looks the way it should if the given idea was correct. Let us assume, then, that the tests were performed and all of them showed that reality looks exactly the way it should if the idea was correct. In our example: we can detect that other galaxies are redshifted, and that there exists a cosmic microwave background - and both effects were actually detected. This means that we are observing a reality that we would expect if there actually was a Big Bang in the beginning.
Does this mean, that the reality actually is the way the idea tells us? If all experimental results match the idea of an initial Big Bang, then there really was a Big Bang?
Strictly speaking - no. Drawing conclusions this way is a logical fallacy called affirming the consequent. Correctness of the idea implies such a reality as we are observing - this doesn't mean, though, that such observations imply the correctness of the idea. I'm writing "strictly speaking", though. In practice, so many experiments are being (and have been) performed, that if a theory derived from an idea matches all of them, it is really hard to imagine another theory, matching the experiments equally well, that would contain the negation of the idea. In our Big Bang example, almost all - if not all - the effects implied by the Big Bang have been detected, so it is really hard to imagine an equally good theory that would not assume the Big Bang, or would even assume a lack of it. A priori, it is possible on a purely logical level - at least until we have an actual proof that the negation of the idea in consideration (the lack of a Big Bang) unequivocally contradicts reality. Nevertheless, even lacking such a proof, an idea can often be considered well-founded - with a caveat that we will cease to consider that if a counterexample is found. So, for the moment we deem the Big Bang as having actually happened, but we are open to the idea that another explanation might arise that would not require a Big Bang.
Neither experiments, nor theories give us any direct information about the objective reality. Obtaining such information is probably impossible, anyway - since every observer has no choice but to study it through their own subjective perception. For this reason, the scientific method focuses on intersubjective verifiability instead - that is, such a presentation of theories and experimental results which allows independent observers to check them and come to the same conclusions, each in their own subjective perspective.
The issue of intersubjective verifiability is simpler for theories. What is needed is an expression of the theory that allows other to independently derive the same predictions from it. This is usually achieved by using rigorous, precise language in formulating theories - often mathematics. If people other than the author can understand which reasonings are correct within the theory, and which are not, the goal has been achieved.
There is a slightly bigger problem with this in the case of experiments. Precise language is also required - it is necessary for other people to be able to recreate both our experimental setup, and the conditions in which we were performing the experiment. But there is still one element missing, and it is specifying what results can be considered the same, and what results can't.
Imagine, for example, that we are trying to measure the Earth's gravitational acceleration with a pendulum - it's a pretty simple experiment, it boils down to measuring the length of the pendulum and its period of oscillations, and using a simple formula. Imagine that we performed the experiment and got a result of 9.8 m/s², and our friend performed it, too, but they got 9.83 m/s². So what now? Does it mean that only one of us got the correct result? Or maybe neither of us? Have we forgotten to take some factor into account...?
The answer is: it depends. It depends on how accurately we measured the length of the pendulum and its period of oscillations. No measurement is perfectly accurate - the instruments have their limitations, and every measurement is distorted by random factors that are impossible to take into account. All of this means that every experimental result has a corresponding uncertainty. The analysis of uncertainties is an important part of the job of every experimental scientist.
When we account for the accuracy of the instruments and other factors, it might turn out that our result with its uncertainty is 9.8 ± 0.1 m/s², and our friend's - 9.83 ± 0.15 m/s². This would mean that not only are our results not contradictory, they are even very much in agreement!
The uncertainties also play a very important role in comparing the experimental results with theoretical predictions. If a theory predicts an acceleration of 9.81 m/s², and we got 9.8 m/s², that doesn't mean that the theory has been falsified yet! If that was 9.800 ± 0.001 m/s², and the theory predicts 9.8132 ± 0.0003 m/s² (yes, the predictions can have uncertainties, too - they are often based on experimental results that have uncertainties themselves), then the theory would be in trouble. But if it is 9.8 ± 0.1 m/s², as in our example, then it is a result matching the theory.
An important part of the scientific method is counteracting the influence of various psychological effects on theoretical predictions and experimental results.
Let us say that we made the measurements of the gravitational acceleration with a pendulum and we got 9.7 ± 0.1 m/s². Then we calculate it from theory and we find that it should be 9.81 m/s². But, we note that we might have measured the length wrong, and by the way, we probably turned the timer on a bit late, and if we just modify some numbers within the error boundaries, we will get 9.75 ± 0.11 m/s². Then we proudly announce that the theory matches our experiment.
All is well until someone else comes, makes the same measurement, gets a non-matching result, and it makes them find the existence of a factor that we missed and nobody else has heard of before. And thus we missed a chance for a huge discovery.
Or another example: consider a simple theory that says "a green color of an object causes it to fall when it is thrown". We set out to test it. We take a few green objects, throw them, they fall. We are proud of our confirmation of the theory. Someone else comes, throws a red object, it falls. Throws a blue one, it falls. Something doesn't really add up here.
These are just two examples of mind traps that one might fall into. A scientist has to be aware of them and actively counteract the possibility of falling victim to them.
The first described effect is usually counteracted by making predictions in advance. Correctness of a theory is studied by first calculating its predictions, and only then performing the experiment. Then one can honestly check if the predictions match or not - and if not, look for the source of the error.
The second effect is called confirmation bias. People have the tendency to look for confirmations of their suppositions. But, if we are looking for a rule that would be as general as possible, we also have to make sure that the predictions are not a match under conditions when they shouldn't, and this part is often overlooked. This is actually the trap that many people fall into when faced with the riddle from the beginning of the article (if you haven't tried it yet - well, know you know what to look out for) and this is why it is important to try to falsify a theory when testing it, and not to try to confirm it.
There are many various effects of this kind, so it is impossible to describe all of them here. I won't even try, then - I'll just say that it is a good idea to research this topic before announcing a revolution in science.
I wrote a lot about what science is and how it works. There is also a phenomenon that tries to pass as science, but is not science - it's pseudoscience. What are the characteristics of pseudoscience? How can you tell it from science? This is a topic for a whole book, I'll just describe a few signs here that should raise red flags when you encounter them.
1. Anecdotal evidence
Pseudoscientists love anecdotal evidence - ie. stories that confirm their claims, but are either hard to verify, or their authenticity is of little importance to the subject at hand. An example of typical anecdotal evidence is "my aunt was taking homeopathic medicine and was cured", or "here on website X a random man described how he performed an experiment and got a result contradicting a well-established theory". In both cases we know nothing about reproducibility of the result - it could be caused by an unknown factor, a random fluctuation, or it could be a straight up lie. In case of medicine, its effectiveness is tested using statistical methods in controlled trials (because even effective medicine doesn't provide a 100% certainty of success in therapy). In the second example, a few independent confirmations would be needed to acknowledge the result - especially if it contradicts the rest of scientific knowledge.
2. Selective treatment of data
A typical move of pseudoscientists is to focus on results that seem to confirm their results, and completely ignoring those that contradict them, no matter how many there are. If somebody ignores results of repeated studies that are inconvenient to them - it's a solid indicator against their often declared scientific approach.
3. Promoting unfalsifiable theories
Pseudoscientists like to propose theories that sound reasonable and explain the observations at the first glance - but if you look deeper, they would explain any observation. Or, in other words - there is no observation imaginable that would prove their theory wrong. No matter what is observed, the theory explains it. "A negative result? I'm right. A positive result? I'm also right."
It is easy to identify such a theory by the impossibility of deriving any predictions from it. Since any result would agree with it, there is no telling which of the agreeing results will happen in reality.
4. Accusing science of being unscientific
This one is particularly amusing, because it is a classical projections of one's own shortcomings on the opposite side.
A typical accusation of being unscientific is based on the fact that a theory is not the only one possible explaining an observation. It stems from a mistaken belief, or purposefully wrong allegation, that scientific evidence cannot admit more than one interpretation. This is obviously absurd. A theory isn't scientific because it is the only one that can explain every single observation, and an obsevation isn't scientific because it only has a single theoretical interpretation. A theory must be falsifiable and match all known experiments (where applicable); an experiment must be reproducible and have rigorously analysed uncertainties. That's it for the scientific requirements.
Theory vs hypothesis
As a closing remark, I wanted to touch upon another topic that often likes to appear in the context of evolution, and that is often explained completely wrong.
In discussions about evolution, its opponents often like to raise the "argument": "evolution is just a theory". A common answer is to state that this mixes the colloquial meaning of the word "theory" with its scientific meaning; that the colloquial "theory" is closer to scientific "hypothesis", and that scientific "theory" is a hypothesis confirmed with observations. The first part is admittedly correct, but the second part is totally wrong.
I wrote what a theory is at the beginning - it is a system allowing to make predictions about reality. There is nothing in the meaning of the word even remotely resembling being confirmed! A theory is a theory regardless of whether it matches experiments (it is "correct"), or whether it does not (it is "wrong").
It is true that the colloquial usage of the word "theory" is as a synonym for a "hypothesis", a "supposition", and that arguing by "it's just a theory" is a simple equivocation. It's not true, though, that a theory is somehow a next stage in the development of a hypothesis, which is reached when the hypothesis is confirmed. Being a hypothesis and being a theory are two independent things. Presenting a new theory is usually at the same time a hypothesis that it is correct, that it accurately describes reality - but this is where relationships between the two end.
It is also worth reiterating that a theory can never be confirmed. It can only be not falsified. If a theory can't be falsified, even though there were attempts - it is considered a good theory.
Well, this came out longer than I expected. I hope that I managed to explain the essence and the sense of science at least a bit, and show what the scientific method is about. The awareness of these issues is particularly important now, when everybody can go and publish whatever in the internet, and pretend to be a scientist even if they know nothing about the topic. This text is supposed to be a kind of a vaccine against such people - it should provide the Reader with knowledge allowing them to recognize if someone is really presenting something scientific, or if they are only pretending. If this is achieved - awesome. If not - well, I just hope that there was something valuable in it regardless :)