Fact vs Theory vs Law vs Hypothesis vs Proof

There is a reasonable amount of jargon across all scientific disciplines and it is absolutely not surprising that the general public does not keep up to date on all of them, nor should they be expected to.  That being said, there are a number of scientific terms that are fairly regularly and consistently misused by the general public and the media that are fundamental to science across all disciplines.First, lets take a look at what science actually is. According to Wikipedia: “science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe”. That is pretty straightforward.  Science is a framework, or a methodology, for looking at the world around us and putting forth our best efforts to understand this crazy universe we find ourselves in. This framework can be laid out in a few simple steps outlined in this nifty little flow chart:
scientific method

Original image created by http://www.sciencebuddies.org/

That is all there is to it.  That is science.  The tricky bits fall within the background research, constructing a hypothesis, designing and implementing an experiment, and analyzing the results. The finer details of these steps may vary from field to field but this is, in essence, what has taken us from tribal nomadic civilization to dropping probes on Mars.  Needless to say, it works pretty well.
Now lets dive into the headline of the article. The words listed in the title, fact, theory, law, hypothesis, and proof are words that find themselves with slightly different meanings in the common vernacular when compared to how they are used within the context of science.  This leads to much confusion in science reporting and in communicating science to the general public.  Please, please, please, keep in mind that when you are reading and listening to scientific discussion of any kind these words must be understood within the proper context and not as they are typically used by the general public in day to day conversation.
Scientific Hypothesis: A scientific hypothesis is a testable explanation about some phenomenon. This could range from an explanation as to why apples fall from trees to why homo-sapiens walk on upright on two legs and well beyond. As long as it attempts to explain something and it is testable it is a scientific hypothesis. There are good and bad hypotheses and the quality of ones hypothesis is likely going to be intricately connected to the original question and the quality and extensiveness of the background research and relevant background knowledge of the individual generating the hypotheis. The key difference between a hypothesis as used in day to day discord and a scientific hypothesis is that a scientific hypothesis is necessarily testable. Hypothesis testing is a whole other issue that I may tackle in the future but for now lets leave it at that.
Scientific Fact: A fact, within the context of science, is very basic.  A scientific fact is in essence an objective and verifiable observation. It is a fact that when standing on the surface of earth if one were to release an object from their outstretched hand that the released object will fall towards the ground. This is an objective reality that anyone can go and test at any time. Facts are collected when we repeatedly fail to reject a hypothesis during experimental testing.
Scientific Theory: Here comes one of the big problems. In general conversation when someone uses the word theory they are using the word the same way a scientist might use hypothesis. The person most likely means that they have some kind of guess or hunch.  When a scientist uses the worth theory they mean something entirely different.  Within the context of science a theory is 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. Further, a scientific theory must be able to be used to make predictions about natural events and phenomena that are consistently accurate. A simple way of thinking about a theory is that is is what we use to explain the facts we observe in the world. Sticking with the gravitation example given above the Theory of Gravity is not a guess or a hunch about gravity.  The theory of gravity is an attempt to explain how and why when you release that object from your hand it falls.
Scientific Law: While a scientific theory may help us to explain the world around us a scientific law is something entirely different.  A law, within the context of science, is a statement that is based on repeated experimental observation that describes some aspect of natural phenomenon. While the theory of gravity may strive to explain why things fall when you release them the a law of gravity will describe the falling.  As such, laws are often expressed using mathematics. It should be noted that a theory can never be “upgraded” to a law as they are completely different things.Proof: This is important. Outside the world of mathematics, science does not and cannot “prove” anything. That is simply not how it works. Continued use of the scientific method builds supporting evidence or refuting evidence for existing theories and laws and is used in the construction of new theories and laws.  That is all there is. If you were reading closely earlier you may have noticed a curious way of describing the outcome of an experiment. “Facts are collected when we fail to reject a hypothesis during experimental testing”.  This is significant and important to understand. An experiment in science does not prove the hypothesis, is either rejects the hypothesis or fails to reject it.  We are inherently incapable of  designing and carrying out an experiment 100% perfectly. Because of this we can never know with certainty that the outcome was not caused by some unaccounted for variable, some bias, or some mistake.  Instead, we slowly chip away at the unknown by demonstrating what is not and raising up what is left for further criticism and refinement.I hope this brings some clarity to the discussion of science and that those who stumble across this find it interesting and useful.Lastly, as always, if you made it this far please share/upvote/and all that other social media jazz!

Edit: If you enjoyed this, you should take a look at my more recent article focusing specifically on the use of “proof” which can be found here: You can’t prove it: On the value of “proof” and the importance of falsifiability

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