It's just a theory

Is a scientific theory no different to the theory that Elvis is still alive? Jim Al-Khalili sets the record straight.

  • Just a theory?

    Credit: Royal Institution

'Just a theory’, the latest animated film from the Ri Channel, is not about telling people what to believe, or that an idea they might hold dear is wrong or misguided simply because a scientist tells them it is and that they should fall in line because the scientist 'knows better'. Rather it is to get across a key idea about how science itself works: what does a 'scientific theory' mean?

We hear all the time that scientific theories such as evolution by natural selection, the Big Bang theory or our latest understanding of how the earth's climate is changing due to human action are 'just theories'. This implies that they are not only open to scrutiny, as they should always be of course, but rather that they can be easily dismissed because scientists cannot 'prove' them.

Because of our broad use of the word 'theory' in everyday language, we tend to assume that a ‘scientific theory’ amounts to the same thing - that it is just an idea that someone has come up with that has no more validity than any other idea. Our aim with this animation is to explain what we mean by a 'scientific theory' - because it refers to something quite specific.

For a theory to be scientific, it needs to do several things: it has to explain some aspect of the world around us; it has to be supported by evidence; and it has to make predictions about other aspects of the world that we can measure or observe. If it does these three things then it qualifies as a scientific theory. This does not mean that it is the absolute truth or the final word on the matter. But it does mean we are able to elevate it above the status of mere 'opinion'.

Everyone can have and is entitled to an opinion, and opinions do not need supporting evidence. Someone may wish to call an opinion their 'theory' but they cannot say it is a ‘scientific theory’ if it does not meet those three criteria. Science works (the scientific method) in a more restricted way.

We believe this film could also be a useful resource for science teachers wanting to convey the subject-specific meaning of “theory” to their students. Showing it to the class after a discussion around children’s understanding of the word might form part of a lesson on “how science works”, for example.  

And who knows, if enough people watch and share the film, perhaps it’ll encourage people to think more deeply before they argue about well-established science and claim that it’s “just a theory”?

'Just a theory' was produced by the Ri Channel team with the creative help of animator Jack Kenny and voiced by Jim Al-Khalili. 

Jim Al-Khalili OBE is a professor of physics, author and broadcaster based at the University of Surrey where he currently teaches and conducts theoretical research in quantum physics. He has also held a chair in the Public Engagement in Science since 2005. He received his PhD in nuclear physics in 1989 from Surrey before working as an SERC Postdoctoral Fellow at UCL. He returned to Surrey and was awarded a five year EPSRC Advanced Research Fellowship in 1994 before being appointed as a permanent member of staff in 1999.

He is active as a science communicator and has written a number of popular science and history of science books, between them translated into over twenty languages. His book, Pathfinders, was shortlisted for the Warwick Prize in 2013. He is a regular presenter of TV science documentaries, including the Bafta nominated Chemistry: A Volatile History and Shock and Awe: The Story of Electricity both for the BBC. For the past three years he has presented the highly successful weekly BBC Radio 4 programme, The Life Scientific. 

Follow Jim on Twitter @jimalkhalili.

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