I find it interesting in the NOVA Megabeasts' Sudden Death show, (http://www.pbs.org/wgbh/nova/evolution/last-extinction.html -March 2009, 52 minutes), the program description on the website refers to a "startling hypothesis that may finally explain" the extinctions of the megafauna in North America 12,900 years ago. Yet in the opening comments of the movie they refer to the idea as a theory. As a scientific educator, I find it interesting to explore the distinction between different terms- hypothesis versus theory- especially in this case, because unraveling the confusion teaches one about the nature or process and history of science.
Theory and hypothesis generally are not interchangeable terms for a scientist; a theory implies that something has been proven and is generally accepted as being true. For many scientists, in the case being discussed, they don't feel there is enough "evidence" to accept the idea that a comet caused the end of the megafauna in North America 12,900 years ago. When it comes to active and new explanatory ideas in science, the line between hypothesis and theory can become blurred. Maybe this is when a "hypothetical theory" becomes a useful term?
For the layperson, a "theory" can mean just a "guess", but not to scientists, where a theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers. Students watching this video and exploring the topic can be challenged to seek and keep track of the "evidence"- all the data that supports the comet hypothesis and then determine why the idea is not yet universally accepted and what it would take to have the "hypothesis" become a "theory".
Generally theories are well documented and proved beyond reasonable doubt. "Yet scientists continue to tinker with the component hypotheses of each theory in an attempt to make them more elegant and concise, or to make them more all-encompassing. Theories can be tweaked, but they are seldom, if ever, entirely replaced," (http://www.wilstar.com/theories.htm). Is this the case with the comet theory described in the movie? Listen and take note of key language being used, like, "Today, a controversial new theory just might explain" the extinction of the megafauna. Ask why is the idea controversial, because it is new, or because it doesn't yet explain everything about the mystery?