Time to be smart: ‘Fact’, ‘Law’, ‘Hypothesis’ and ‘Theory’ in Science.

Reading time: 2 min 57 sec

I watched a youtube video recently wherein
Dr Zakeer Naik says to a bright medical student that a theory in science will become law/fact after testing and evaluating it using scientific methods over time. I got shocked listening to this nonsense. There is no wonder when a religious person says something like this because the lack of scientific knowledge can lead him to the highest level of misconceptions (I know people who still believe that Earth is the centre of the universe! yes. They exist!). Instead, why I got shocked was because he is educated scientifically and has earned an MBBS degree. It seems that there is a lot of people out there who have confusions about differences between terms such as fact, law, hypothesis, and theory. I believe that at least people who do science should know the differences. Otherwise, a lot of misconceptions will lead them to believe in absurdities. So here we are…

The terms above have other meanings in everyday English vocabulary, but in science, they have definite meanings:

  1. Fact: It is an observation of a phenomenon/event that has been repeatedly confirmed and finally accepted. It is always true under specified circumstances. E.g.:
    • “When I drop objects, they fall on the ground.”
  2. Hypothesis: A proposed explanation of the observed fact (A hypothesis can become a law or a theory as you will read further down the article). E.g.:
    • “Some mysterious force is located at the centre of the earth. It continuously attracts every object towards it.”
    • “Every object attracts each other. So objects fall as a result of the earth’s attraction.”
    • “Not every object attracts each other, but only earth attracts all other objects. My pencil never seems to be attracted by my pen.”
    • “Every object has its own natural state, and this state is acquired when an object is at the centre of the universe. Since the earth is the centre of the universe, objects tend to move towards the earth’s centre.”
  3. Law: A law describes the working of a fact. This description never tells us why it works, instead it only tells us how it works, most often backed up by mathematical equations. E.g.:
    • “A man named Newton sits alone inside his house for years and finally comes out one day, hypothesises that objects attract each other by a force that depends on their masses and distance between them. He formulates mathematical equations describing his observation. Independent tests over more than 300 years validate these equations, and people start to consider these as the laws of gravity. All other hypotheses fail the tests and thereby become wrong descriptions.”
  4. Theory: A theory explains why an observed fact works. It tells the mechanism involved. A theory can be founded with a set of postulates. A hypothesis/group of hypotheses can become a theory when it is tested and verified scientifically. But no amount of supporting experiments can prove that a theory is always right because scientists entertain the possibility of anomalies in theory. A theory should also confirm all its predictions by undergoing rigorous experiments. In case of failure of some predictions, this theory should either be modified or corrected. In fact, the more a theory survives under different circumstances, the closer the theory resembles the actual mechanism involved. In this sense, only science can lead to the truth by convincing everyone. E.g.:
    • Einstein’s general theory of relativity explains why gravity works the way it does. Because of the uneven distribution of mass, the space-time around it will be warped, which in turn pushes objects to move along specified paths.

No wonder why people mistake the word “Scientific theory ” as “hypothesis”. Internet says “theory” and “hypothesis” are synonyms: wrong

What internet says is right, but then people misinterprets that a ‘scientific theory’ and a ‘theory’ are the same. But they are never the same.

Some people think that a theory becomes a law when it is tested and verified over time. This is just false. They are all independent terms in science, as explained above.

Next time if someone says that ‘Theory of Evolution of species’ is just a theory and wrong at that, then you can confidently ask them to learn first the meaning of what a scientific theory is. It is time to be smart. 🙂 


  1. The Role of Theory in Advancing 21st Century Biology, National Academy of Sciences
  2. http://oregonstate.edu/instruction/bb317/scientifictheories.html
  3. A great youtube video on this topic explained by Joe Hanson, PhD.


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