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Science discusses alternative models and interpretations.

January 19, 2012

When you think you’ve got a perfectly good explanation for something, why would you want to dream up another explanation or two?

This is one of ScienceOrNot’s Hallmarks of science. See them all here.

In short…

Scientists must actively address alternatives to their own preferred models. A scientific model is valid only if alternative models have been considered, tested and shown to be wrong.

If there’s something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among “multiple working hypotheses,” has a much better chance of being the right answer than if you have simply run the with first idea that caught your fancy.

Carl Sagan, American astrophysicist, 1996

Where do alternative models and interpretations come from?

Scientists who are investigating a phenomenon often propose a number of alternative models. This is an important creative stage in science. Each scientific team needs to think laterally and consider as many plausible models as possible, with the ultimate aim of eliminating all but one. Other scientists working in the same field may also contribute competing models.

What happens to the alternative models?

In the early stages of investigation of a phenomenon, there are usually a number of models.

In the real-world testing of models in any scientific field, the tests should be designed so that they will eliminate some of the models. As the field matures, the number of accepted models decreases until a single model usually dominates. In some cases, aspects of the abandoned models may be incorporated into the surviving model.

Why alternative models are needed

By contrasting different models, scientists highlight where research should be directed in order to distinguish between them. A surviving scientific model has greater value when rival models have been tested and eliminated because scientists can then explain why those discarded models do not fit the phenomenon being investigated.

Bogus scientists tend to latch on to a single, idiosyncratic model which remains untested.


  • The consensus of climate scientists is that the current episode of global warming is is being driven principally by increases in greenhouse gases due to fossil fuel emissions. They have examined all feasible alternative explanations, such as variations in solar radiation, cosmic radiation, urban heat islands, aerosols, the Pacific Decadal Oscillation and volcanic eruptions. All of these have been eliminated. For a summary, see here.
  • A 2007 study investigated two different models for a stage of human evolution, one proposing that our species replaced earlier species and another proposing that it interbred with them. The evidence supported the replacement model.
  • One of the earliest explanations of continental drift was S Warren Carey’s expanding earth model. Carey and others continued to defend the model during the 1950’s and 1960’s but accumulating evidence for the Plate Tectonic model saw its gradual demise.
  • In the mid-twentieth century, there were two rival models for the origins of the universe – the Big Bang theory and the Steady State theory.  The discovery of the cosmic microwave background in 1963 settled the argument in favour of the Big Bang. Recently. researchers at the University of Melbourne have proposed a new model which proposes that the origin of the universe was similar to crystallization.
  • Homeopathy is based on a model known as ‘the law of similars’ which claims that a substance that causes symptoms similar to an ailment can, when highly diluted, be used to treat that ailment. This model was proposed in the 19th century by Samuel Christian Friedrich Hahnemann as an alternative to other contemporary medical theories. It has not been abandoned by homeopaths, despite lack of supporting evidence. Homeopathy cannot claim to be scientific.

Carl Sagan’s quote is from The Demon-Haunted World, Ballantine Books, NY
The Big Bang/Steady State cartoon is from Ideas of Cosmology, AIP.
This is one of ScienceOrNot’s Hallmarks of science. See them all here.

This page reviewed 2013/09/12

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