You may have heard how someone disparages evolution - "it's just a theory." On the other hand, gravity must be 100% real - after all, it is "law." But these general impressions are not entirely correct. The words "fact", "hypothesis", "theory" and "law" have very specific meanings in the world of science, and they do not quite correspond to those we use in everyday language.
Fact
This is a fairly simple fact, but not so simple. In science, a fact is an observation that has been confirmed so many times that scientists can, in every sense, accept it as "true." But nothing is scientifically absolutely “true”. You can say that "all swans are white" is a fact, but there is always a chance that you will see a black swan and the fact will cease to be true.
Likewise, you could say that in fact, every time you drop your pencil, it falls to the floor, but science leaves room for the infinitesimal probability that this may not happen (for example, in zero gravity).
Hypothesis
A hypothesis is a preliminary explanation for an observation that can be tested. This is just a starting point for further investigation. Any observation is usually accompanied by many hypotheses. If you notice that a swan is white, your hypothesis might be that it is dyed, or its feathers are faded in the sun, or its feathers simply lack pigment. You can then explore all of these hypotheses and find the one that is most supported by the evidence, if any.
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Throughout history, there have been many hypotheses about why objects fall when you drop them. Aristotle believed that this is because material objects tend to fall towards the center of the universe, and the ancient Greeks considered the earth to be the center of the universe. Newton reasoned that all Earth-related objects should be attracted to the Earth, but also all planets should be attracted by other planets, and so on for every object in the Universe. His hypothesis was that all this is due to the force of gravity, which he called gravity.
Law
In science, a law is a detailed description of some phenomenon in the natural world, usually involving mathematics. Newton's law of universal gravitation, quoted above, describes with impressive accuracy how matter behaves. This makes it easy to predict how the Moon will behave if it is very large and close to its planet, and not the way it is now - very small and distant. The law describes all this, but does not explain why.
Theory
A theory is an explanation of some phenomena of the natural world, which are confirmed by facts, tested by hypotheses and laws. The above quote is a simplified version of Einstein's general theory of relativity. Newton said that the force of attraction between two objects depends on their mass and the distance between them; Einstein said that attraction occurs because the mass of each object literally distorts the fabric of the universe, and the greater the mass, the greater the distortion.
Theory is the grandfather of all scientific statements, so it makes no sense to say that evolution is "just theory."
But, as already mentioned, science never says anything with 100 percent certainty. Einstein's theory doesn't work when you apply it to quantum mechanics, which deals with the behavior of tiny subatomic particles. As a result, many scientists are putting forward new hypotheses about gravity. But that doesn't mean Einstein was wrong. General relativity explains the vast majority of our observations, and every time scientists tried to prove it was wrong, they failed. This is the strength of scientific theory: it is built on a sufficiently solid foundation that even if you find several cracks in it, you can be sure that the structure as a whole will hold up.
Svetlana Bodrik
