What to Believe? Scientific Explanations

Look at the photo below. Do you believe what you see?

image of big foot
Source: Roger Patterson’s Sasquatch, History Link

On October 20, 1976, Roger Patterson and Robert Gimlin set out on horseback to explore the northern California wilderness and search for Bigfoot. Using a 16mm handheld movie camera, they shot the following footage.

Source: Roger Patterson Bigfoot footage, Dzvid Walker 1964

Many scientists throughout the world continue to remain divided on the authenticity of the film. 

When we are asked to evaluate scientific explanations, we have to evaluate or judge the reliability of what we hear and see. We have to use critical thinking to evaluate explanations. Critical thinking means combining what you already know with new facts or observations and deciding if you agree or not.

Evaluating scientific explanations involves two steps.


Hypothesis vs. Theory

In everyday language, people often use the terms hypothesis and theory interchangeably. For example, when a person makes an observation about everyday occurrences, he or she might say, “I think that she speeds to work every day; that’s my theory.” In most cases, this is not a problem because the meanings of the words are close enough that you will be understood.

When studying science, however, the distinction between the terms hypothesis and theory is important, and it is easy to confuse them. They both refer to a scientific explanation about how the world works. In this lesson, you will look at the definitions a little more closely to try to better differentiate between the two terms.

The chart below shows the differences between hypothesis and theory.

Hypothesis Theory
  • A hypothesis is a possible (tentative) scientific explanation or prediction of an observation or set of observations.
  • In general, a hypothesis is based on a rather limited set of data.
  • A hypothesis must be testable through a scientific investigation.
  • Observations gathered during investigations provide evidence that either support or do not support hypotheses. If evidence supports the hypothesis, the hypothesis is said to be valid.
  • Usually one or more scientists working together make hypotheses.
  • A theory is a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. A theory is used to explain many different hypotheses about the same phenomenon or a closely related class of phenomena.
  • Scientific theories are well-established and highly-reliable explanations that have been verified multiple times by repeated testing and have a great deal of empirical evidence that confirm them as valid.
  • Scientific theories are capable of being tested by many different scientists working independently of each other.
  • A theory is valid as long as there is no evidence to dispute it. Theories can be disproven.

Let’s look at an example of each and see if you can tell the difference between a hypothesis and a theory.

You Try!

Read each of the following scenarios and decide if it is a hypothesis or a theory. 

A Closer Look at Theories

In this section, you are going to take a closer look at theories.

The information that scientists “know” to be “true” is actually based on the accepted scientific theories that have the greatest support. In this section, you will learn about a few of the theories that are currently a part of the scientific community. You may have heard some controversy surrounding some of the scientific theories found in the links below. Investigate each of the links below, and then select two different theories that you would like to investigate further.

After you select your two theories from the list below, answer the questions following the links based on the articles you’ve read. Record your answers in your notes.

Read more about the Big Bang Theory at the following link: The Big Bang

Read more about Atomic Theory at the following link: Dalton's Atomic Theory

Read more about the Cell Theory at the following link: Cell Theory

Read more about the Plate Tectonic Theory at the following link: Plate Tectonics

  1. How does this theory relate to the information you have learned during this lesson about the characteristics of scientific theories?
  2. How do scientific hypotheses help support this theory?
  3. What current investigations do you know about that are related to this theory?
  4. You may have heard that some of the theories you investigated were controversial. How do the characteristics of scientific theories relate to the controversy?

Compare and Contrast Theories and Hypotheses

Now that you have had an opportunity to gather more information about scientific hypotheses and scientific theories, see if you can complete the Venn diagram below using some of the defining characteristics of both scientific hypothesis and scientific theory.

Drag each word in either the Hypothesis, Theory, or Both bubble.