How to Read Science Research, Chapter 3: What Do We Mean By Theory, Fact, Law, and Hypothesis?

We’ve recently discussed where to find peer-reviewed research. Today, let’s talk about some of the words you might see in and about peer-reviewed research: theory, fact, law, and hypothesis.

These vocabulary words are tossed around freely, often by news media reporting on science and angry people criticizing science, without a lot of discussion of what they mean.

Hypothesis

Let’s start with a hypothesis, because that is often where scientists start. A hypothesis is a prediction and is often a starting point for scientific research, and might explain why something happens. A lot of us learned that a hypothesis is an “educated guess”, although we didn’t actually learn a lot about what that means.

A hypothesis is usually not when a scientist looks out the window and makes a guess about why something happens. That might be where it starts, but not where it ends up. A hypothesis usually involves a lot of time spent looking into all the research that has been done on the topic. It often even involves consideration of which type of experiment is most likely to find useful data that supports or refutes the hypothesis. At the end of the day, the science that is going to be funded is the science testing the most promising and well-researched hypotheses, so hypotheses tend to be pretty solid.

A hypothesis has to be tested many times, in many different ways, by many different scientists, before it becomes a theory, so hypotheses can even be supported by quite a bit of data.

Theory

Once a hypothesis has been tested with many experiments by many scientists over a lot of time, and is supported by loads of data, it becomes a theory. Theories aren’t likely to change with new experiments, data, or observations. Theories are usually well-supported explanations of why things happen and are used to make new hypotheses. An example of a theory is germ theory, which explains that (much) disease is cause by germs.

Theories are the best supported information in science.

Law

If a theory is the best supported information in science, then what is a law? A law is a description of something that happens and has been directly observed many, many times. It does not explain why or how. It is often represented by an equation that describes the relationship between different variables. An example of a law is Newton’s 2nd Law of Motion, which is represented by the equation F=ma, and describes the relationship between force applied to an object, the object’s mass, and the object’s acceleration.

We can’t directly observe germs causing disease, which is why germ theory isn’t a law. We’re pretty darn sure of it, though.

Fact

“Fact” is sometimes used interchangeably with “theory”, and sometimes with “law”, but isn’t exactly specified in science. It’s more of a general everyday word than a technical jargon word.

“Fact” isn’t really used a whole lot in science, and for a really cool reason. In fact (ha), this is my favorite part of science. This is what makes science so important: science is never, ever done learning. Science is always open to revising ideas based on new data. Even when we’re really, really, really sure of something, we’re always open to learning something new and changing our minds.

Stay tuned for Chapter 4: How Experiments are Designed!

Sources:

https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Map%3A_Introductory_Chemistry_(Tro)/01%3A_The_Chemical_World/1.03%3A_Hypothesis_Theories_and_Laws

https://lifehacker.com/the-difference-between-a-fact-hypothesis-theory-and-1732904200

https://en.wikipedia.org/wiki/Hypothesis

https://ncse.ngo/definitions-fact-theory-and-law-scientific-work