• Question: Have you did(in your mind) any thought experiment? How does thought experiments help scientists to get new ideas and find new theories?I know that many scientists do a lot of thought experiments but how does a scientist think the right thing even though they are not actually doing the experiments.

    Asked by rajathjackson to Chris, Dave, David, Jack on 26 Jun 2013.
    • Photo: Dave Farmer

      Dave Farmer answered on 26 Jun 2013:

      Hi rajath,

      I would imagine that most scientists do thought experiments very often, even if the don’t realise what they’re doing. An example for me might be imagining a new sample structure and thinking about how a sound pulse might travel through it, and whether there’s anything interesting I could do with it. I don;t formalise this to myself as a thought experiment, but that is essentially what it is.

      Of course we don’t for sure that we’re right until we do a physical experiment, but a good scientist will be able to imagine what the consequences might be, before actually measuring it, based on his knowledge and experience of the subject. This is how you can form a hypothesis that you can then investigate experimentally.

      Hope his helps,


    • Photo: Jack Miller

      Jack Miller answered on 26 Jun 2013:

      Hi Rajath,

      Dave has hit the nail on the head — we don’t often go ‘Right, I’m going to have a thought experiment now’, but we do often wonder things, like when sitting in the bath. If I could detect every neutrino ever, what would I expect to see from the very early universe? It’s these sorts of ideas that occasionally go somewhere.

      Hope that helps,

      — Jack

    • Photo: Chris Mansell

      Chris Mansell answered on 26 Jun 2013:

      Hi rathajackson,

      Thought experiments can be used to think through all the implications of a theory. A famous example is the twins paradox (which was mentioned in the answer to your question about time dilation and living longer). Other famous examples include Schrödinger’s cat and Maxwell’s demon. Thought experiments try to check the consistency of a theory. If a theory is inconsistent with itself (i.e. if it has a contradiction), then there is a serious problem with it. This problem then needs to resolved by seeing how this inconsistency arose.

      In short, thought experiments are used to pinpoint problems with a theory. Being able to do thought experiments is a useful skill for a theoretical physicist.