![]() For example, the law of gravity says that two objects will exert their gravitational pull on each other. ![]() A scientific law describes a scientific observation but doesn’t attempt to say why or how it happens, whereas a scientific theory explains exactly why or how it happens. ![]() The theory of evolution, for example, explains the incremental changes of all life forms on Earth over billions of years. Hypotheses also tend to be very specific, whereas scientific theories are sweeping explanations that cover a wide range of questions about a phenomenon. So what’s the difference between a scientific theory, a scientific hypothesis, and a scientific law? A hypothesis, unlike a thoroughly tested scientific theory, is an educated guess that has not yet been fully tested or subjected to research. In other words, a scientific theory is an in-depth, wide-sweeping explanation of a natural occurrence that can’t be proven wrong given our current scientific knowledge. ![]() That’s because a theory is not just a single answer but a consistent system of many, many answers backed by supporting evidence. For example, if you have big questions about the movement of the planets in our solar system, the theory of heliocentrism has big answers (spoiler alert: they orbit around the sun). You can see some of the turtle specimens that we used in this research in The Field Museum's exhibition Specimens: Unlocking the Secrets of Life, open through January 7, 2018.If you ever stop to wonder why some fundamental process happens the way it does, it will most likely be a scientific theory that has the answer you seek. If you would like to learn more about this research, the scientific paper describing the work can be found in the Journal of Vertebrate Paleontology. For now, though, our results can be added as a piece of evidence that is consistent with the predictions of the large explanatory theory of evolution. Or they might collect data from more turtle species that shows that our results were based on a false pattern stemming from sampling too few species (we considered 47 species in our dataset, about 14% of living turtle species). For example, other researchers might develop a better model of natural selection that shows that our model was overly simplistic. In general, the shell shapes of our aquatic turtles were more streamlined but weaker than those of our land turtles, and our mathematical model of natural selection indicated that selection for streamlining was acting more strongly on the aquatic species.Īs with any idea in science, our results are open to further testing. Our results corroborated our hypothesis that aquatic turtles are forced to make more of a trade-off between strength and streamlining than turtles that live on land. The theory of evolution states that the process of natural selection should work to optimize the function of an organism's parts if the changes increase the chances of the organism successfully producing offspring and the changes are heritable (i.e., can be passed down from generation to generation). That's all fairly abstract, so let's look at a concrete example involving some recent research I undertook with a group of collaborators. If it survives additional scrutiny, she may eventually try to incorporate it into a larger theory that helps to explain her observed phenomenon and relate it to other phenomena. If the hypothesis is corroborated (i.e., not falsified) by the test, the scientist will retain it. ![]() If the test falsifies the hypothesis (i.e., shows that it is incorrect), she will have to develop a new hypothesis and test that. She then devises a hypothesis about the explanation of the phenomenon, and she designs an experiment and/or collects additional data to test the hypothesis. A scientist makes an observation of a natural phenomenon. With these definitions in mind, a simplified version of the scientific process would be as follows. ![]()
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