1.4 We Study the Earth Using the Scientific Method

There is no single method of inquiry that is specifically the “scientific method.”  Furthermore, scientific inquiry is not necessarily different from serious research in other disciplines. The key features of serious inquiry are the following:

  • Creation of a hypothesis. This is a tentative idea about how to explain the observations that have been made.
  • Figure out a way to test the hypothesis.  This usually involves making predictions using that hypothesis, then coming up with a way to see if those predictions are accurate.

For example, if we went on a field trip to a stream, we might notice that the cobbles in the stream were rounded off rather than having sharp edges on them (Figure 1.4).  We might hypothesize that the cobbles became rounded off as they were carried along by the stream, crashing into each other and breaking pieces off.

Hypothesizing about cobbles in a stream. [SE]

Figure 1.4 Hypothesizing about cobbles in a stream. [SE]

If our hypothesis is correct, then we should see the cobbles become rounder and smaller the further we go downstream. That would also mean the cobbles upstream would be more angular and larger.  If we are patient we could also test this by marking cobbles in some way and then checking back to see if they have become smaller and more rounded off over months to years.

If our predictions turn out to be correct, we still have to be careful about how much certainty we attach to our hypothesis.  Although our hypothesis might seem the only reasonable explanation, someone could argue that we might have the mechanism wrong- that cobbles bumping into each other isn’t what rounded them off.  If our experiment didn’t specifically check for the mechanism (say, by watching chips fall off the cobbles and seeing them become progressively rounder), then we would have to acknowledge the possibility.  That doesn’t mean we have to abandon our hypothesis as a useful tool for making predictions.  It just means we have to be open to the possibility that other things might be going on, and if someone demonstrates conclusively that we are wrong, then we have to discard the hypothesis and come up with a better one.  As you will learn later, both our hypothesis and the critic’s comments have elements of truth.

A key element of a good hypothesis is that it is testable.  Someone might argue that an extraterrestrial organization creates rounded cobbles and places them in streams when nobody is looking. This may indeed be the case, but there is no practical way to test this hypothesis. Most importantly, there is no way to prove that it is false, because even if we never see the aliens at work, we still can’t say they haven’t been- we might just have missed it. The key to dealing with this kind of hypothesis is to file it under “not particularly helpful at the moment” and continue to work on hypotheses that seem to be yielding good predictions.

Two other terms are important parts of the scientific method: theory, and law. A theory starts out as a hypothesis, but over a long period of time and a great many tests, it has never come up short. That doesn’t mean it never will, but the odds of that are very unlikely given our present (and conceivable future) state of knowledge.  You may have heard someone dismiss an idea by saying it is “just a theory,” but they are using the term incorrectly if they mean to say it’s a wild and unproven guess.

A law is more of a description than an explanation.  For example, you could do thousands of tests by dropping an object with known mass off a high point and measuring its acceleration and the force with which it hits the ground.  Again and again your results might yield the formula force = mass x acceleration.  However, that doesn’t mean you know what is responsible for the force accelerating it toward the ground.  Yes, we say that gravity is pulling it toward the Earth’s surface, but why?  It’s still a big puzzle why masses attract each other, although scientists are using particle accelerators to test their hypotheses.

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