• Question: What is life?

    Asked by waddle to Carla, Madgie, Nick, Vicky, Werner on 15 Nov 2013.
    • Photo: Werner Muller

      Werner Muller answered on 15 Nov 2013:

      This question can lead to very complicated answers. The short and simple answer is something that can replicate. (And I do not mean computer viruses).

      Erwin Schroedinger wrote a famous book about this question in 1944 (http://whatislife.stanford.edu/LoCo_files/What-is-Life.pdf). This book influenced a lot of physicists to start to work on biology and this in turn had a big impact on biology and medicine as we know it today.

    • Photo: Nick Groves-Kirkby

      Nick Groves-Kirkby answered on 19 Nov 2013:

      This is one of those questions that we don’t really know the answer to!

      Here’s the definition of life I learnt in school (remembered by the acronym ‘MRS GREN’):
      Movement
      Respiration
      Sensitivity
      Growth
      Reproduction
      Excretion
      Nutrition

      If something does all (or almost all of these things then we say it’s alive). For things like humans, plants, insects and even bacteria it’s pretty easy to show they do all these things. Similarly, it’s straightforward to show that rocks and metals aren’t alive.

      However, there are serious questions about whether things like viruses (the kind that give you flu) are alive. They don’t do all of the things on the list, but they do some of them. They’re certainly important to living things, and biologists are still not really sure how to categorise them.

      Werner raises an interesting point though. What would it take for a computer virus to be ‘alive’? I reckon you could design something that has most of the MRS GREN characteristics!

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