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

Scenario 1
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. Is this a hypothesis or a theory?

 

Check your answer Hypothesis - Sue is drawing a conclusion 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. Close

 

Scenario 2
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. Based on this, 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?

Check your answer Theory - 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. Close

 

Scenario 3
Jerry is a passenger in Jane's car, while Jane is driving down the freeway at a constant speed of 60 miles per hour. On a lark, Jerry rolls down his window and attempts to drop a nickel straight down. He immediately observes that the coin falls "backward" as it leaves his hand. Since he has several coins in his pocket, he repeats his experiment with a penny, a dime, and a quarter, and observes similar results. He concludes that objects only fall straight down when there is no horizontal motion involved. Is this conclusion a hypothesis or a theory?

Check your answer Hypothesis - Jerry didn't consider other causes for his observations, such as air resistance. In addition, Jerry didn't have several friends run the same experiment, so his results have not yet been reproduced by others. Jerry's hypothesis is easy to refute by repeating the same experiment inside the car with the windows rolled up. In such a case, Jerry will note that all dropped objects appear to fall straight down in the absence of outside forces, such as air resistance. Close

 

Scenario 4:
A certain biologist visited elephants at a zoo. He felt the air around him throbbing. When the scientist felt the air vibrating, he noticed that the skin on the elephant's foreheads moved. He also noticed that the elephants seemed to communicate without sound. Even though they did not make noise, they would start moving or stop moving at the same time. Using what he knew about whales and how they made sounds too low for humans to hear, the scientist thought that maybe elephants used low sounds like whales to communicate with each other. Is this conclusion a hypothesis or a theory?

Check your answer Hypothesis - The scientist is considering a single event. He makes observations, applies prior knowledge, and proposes a hypothesis. Close