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 we 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.
Read each of the following scenarios and decide if it is a hypothesis or a theory. Click on the term you think is correct to check your answer.
Sue is camping and decides to drop a rock off a cliff. She finds a small rock, drops it, and notes that it takes approximately two seconds to land. She then finds a somewhat larger rock and concludes that the bigger rock should take less than two seconds to land because it is bigger.
Correct! Sue is really hypothesizing that different sized objects fall at different rates, based on a very limited amount of observational data. This hypothesis can easily be tested by dropping two different sized rocks at the same time. Incorrect
John is an amateur astronomer who is in his second semester of high school physics. Accordingly, he knows that objects in motion remain in motion and move at constant velocity in a straight line until some force acts on them. John observes that all of the planets in this solar system orbit the sun in approximately circular orbits. In addition, the farther a planet is from the sun, the longer it takes for that planet to complete one orbit. John discusses his observations with like-minded friends, who also observe and verify what John has seen. Based on these consistent observations from many different people, John concludes that there is gravity in outer space. Is this conclusion a hypothesis or a theory?
Incorrect Correct! John and his friends have each made multiple observations of several different planetary bodies and have concluded that some force is acting on all of them to cause their paths to differ from straight-line paths. Since these planets are obviously in outer space, this leads to the theory that there is gravity in outer space.