As humanity evolved from living in caves and hunting and foraging for food into civilisations, they developed a curiosity about themselves and the world around them. It was soon realised that it is pretty much impossible to discover all the secrets of the universe in one go. Exploring the mysteries of the cosmos involved constantly evolving knowledge and beliefs. Therefore, a systematic mechanism to conduct this exploration was required. As a result of this, the scientific method was born. This method facilitates humans in investigating various phenomena, evaluating and re-evaluating existing knowledge, and expanding the boundaries of what is already known. As such, adherence to the scientific method has become an integral part of scientific inquiry and any scientists wishing to share the results of their research with the world are expected to follow it.
One of the many benefits this process affords is to weed out the bad theories from the good ones. A theory that passes the filters of the scientific method can be considered robust and highly likely. However, in many cases, it is equally important for scientists to communicate their results to the world at large; to people who may not be trained in the use of the scientific method, and indeed may not even understand it. To one unfamiliar with it, the constantly evolving nature of scientific knowledge raises serious questions about its trustworthiness at any given point in time. Therefore, I believe it important for every intelligent and thinking human being to be familiar with the basics of this method so that they may begin to trust the scientific process and the knowledge it reveals.
It is important to distinguish the term “scientific theory” from “theory” in the general sense. The AAAS defines a scientific theory as “a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.” What does this mean in simpler words? It means that there are numerous natural phenomena around us. In order to understand them, we must come up with some kind of explanation as to why they occur. This explanation is known as a scientific theory. What characteristics must a scientific theory possess to be considered plausible? It must explain the observed facts, as well as make some measurable predictions that can be repeatedly tested under controlled conditions. A theory that possesses these two characteristics is a good candidate to explain the actual phenomenon. This definition also provides us with a hint about the scientific method, the application of which results in a scientific theory.
The scientific method consists of asking a question about the phenomenon being investigated, formulating a hypothesis (a conjecture about the phenomenon that can be proven true or false), evaluating the logical consequences of that hypothesis, and testing these predictions. The final step in the scientific method is the analysis of the results of the previous steps to determine if there is enough evidence to prove or disprove the hypothesis and to rule out the possibility that the evidence is observed as a random fluke. To evaluate a theory using this method, a hypothesis is chosen. This hypothesis represents some aspect of the theory and must be true if it is correct. There may be several such hypotheses that may be true given a particular theory. The more hypotheses are proven correct using this method, the more a scientific theory is considered to be plausible. A good theory is one that withstands such scrutiny over a considerable period of time without being falsified. For example, one question might be, “why is the sky blue?” A hypothesis might be, “elements in the air bend the light in such a way that render the light blue.” This hypothesis presents some testable predictions; there must be some elements in the air that affect the light and the light’s wavelength must change after hitting them. These predictions can then be tested in a laboratory to see if they support the hypothesis.
This means that there is no such thing as a completely certain scientific theory. Every theory exists on a likelihood spectrum. The more a theory is supported by evidence, the more likely it is. This begs the question; what happens if evidence that contradicts a theory is observed? Well one of two things: if the theory is still new, then most likely an alternate theory will be proposed that explains all of the previously seen evidence as well as the newly observed one. If the theory has been extensively tested in the past, it is more likely that the existing theory will be modified slightly to explain the new facts. Generally speaking, the more a theory is tested, the less likely it becomes that it will be completely wrong.
A classical, yet controversial example is the Big Bang theory. This theory attempts to explain how our universe came to be the way it is. The basic postulate is that at one point in time, the universe existed in a super-dense, super-hot state. The rapid expansion of this state allowed the super-hot energy to become less dense and cool down, giving rise to our universe. According to recent estimates, the “explosion” that caused the rapid expansion occurred approximately 14 billion years ago. Eventually, the cooled energy transformed into matter, which in turn gave rise to planets and stars. To this day, our universe is still expanding. Now one might wonder, how do you test something of this magnitude and proportions? How can you find out what happened 14 billion years ago when no planets, galaxies, suns, moons and stars existed? The sheer scale of the phenomenon is overwhelming and mind-boggling. How did humans even come to imagine such an elaborate story? What prompted the idea in the first place?
To answer, we shall look at a little bit of history. Scientists did not always believe that the universe was expanding. Initial models of the universe depicted a static universe. One in which the positions of the various celestial bodies were fixed. The first discovery that indicated that this might not be the case came in 1910 when Vesto Slipher, an American astronomer, and later others observed that the light from most spiral galaxies was red-shifted. This means that the observed colour of light from these galaxies was redder than it originally was. Red-shifting of light is a well-known phenomenon that occurs when the light source is moving away from the observer. In addition, Einstein’s general theory of relativity did not allow for a static universe. It predicted that the universe must either be shrinking, or expanding. This led Einstein to believe at first that his calculations were wrong. But in 1929, Edwin Hubble discovered that relative to earth, all other celestial bodies are receding in every direction. Hubble’s calculations were found to be consistent with general relativity, causing scientists to seriously begin considering the expanding model of the universe. His discoveries later led to the development of the Big Bang model.
With the development of the Big Bang model came testable predictions. Over the years, many of these predictions have been found to be correct. Probably the most important prediction of the Big Bang was the existence of an extremely faint background glow in the universe, invisible to the naked eye. This glow is a remnant of the very early stages of the rapid expansion of the universe when it was filled with opaque light. Eventually, this light cooled and became transparent. Two American astronomers discovered this glow in 1964. This discovery is considered a landmark test of the Big Bang model and earned the two astronomers a Nobel Prize in 1978. Since then, many more predictions of the Big Bang model have been found to be correct, establishing it as the dominant model of the evolution of the universe in current times.
This example clearly demonstrates how application of the scientific method, from asking questions, to developing theories based on facts, to testing these theories helps further our understanding of the universe. The point of emphasis here is that scientific theories are not just random guesses by scientists that they either choose to believe or discard. Well-established scientific theories become so only after rigorous testing and experimentation. Therefore, to say that a well-established scientific theory is just that, a theory and could be wrong is to undermine the hard work of many scientists spread over many years. This is not to say that any theory, such as the Big Bang, is fool proof and cannot be wrong. However, given the abundance of evidence observed in its support, it is highly likely that it is mostly correct. It is still entirely possible that future evidence leads scientists to refine or alter it a little bit to better fit the facts. However, that must not be taken as a sign of the fragility of science and considered as a shortcoming. Science, while being transient, is still based on observed facts. To deny it is to adopt an “ostrich” mentality. We must avoid that at all costs lest history leave those who would deny the truth behind.