You know a fundamental question when anybody can ask it and everybody has an answer, while professional scientists struggle.
We interviewed prominent scientists who said they could not define what "life" is.
That made for a tricky broadcast because we spent the next 50 minutes using substitute phrases such as "biological processes". It was like a conversation about dancing where you couldn't use the word "dance".
"Some say 'we don't know what life is, but we know it when we see it'', they quipped.
The most extreme definition is a purely physical one with the intimidating label, "far-from-equilibrium dissipative system".
By that definition, a cyclone and even a star are forms of life. They both are systems that disperse energy.
A more familiar and less strict definition is easily observable. A cat, a tree and your friend are all obviously living biological organisms. They have seven dimensions in common.
The first is that life has a chemistry that transforms energy and produces waste (ie, it has a metabolism).
An organism is able to grow in a controlled way.
It has a regulating mechanism such as sweating to control temperature.
It is organised into one or more cells.
Organisms adapt to changes in the environment and can evolve over time.
Life can respond to stimuli such as when a plant grows towards light.
Life can reproduce.
The problem then is that most of these dimensions can be violated. Some species have remained unchanged for billions of years. Some are almost completely static because they don't grow, or lie dormant for extended periods.
And so on and, as the list grows, our definition begins to look tatty around the edges.
While the life we know is carbon-based, this is not essential because it's possible to imagine a chemistry based on silicon.
Perhaps there are examples of this somewhere, but silicon does not offer the same richness of combinations that is possible with carbon.
Then there's the vexed question of whether viruses are alive, or are they just complicated molecules with the ability to replicate?
The virus now preying upon humans is a wily opponent, and whether it's an example of life is extremely unclear.
If the Rona cannot function outside a host such as a human, is it living or not?
The goal of a virus, if there is such a thing, is to replicate, and collateral damage to its host is otherwise irrelevant.
There are other definitions of life, each with their own limitations.
Perhaps all this suggests that science can sometimes be too rigorous because, after all, we know what life is.
Or maybe we should quote Marvin the Paranoid Android: "Life. Don't talk to me about life."
The Fuzzy Logic Science Show is 11am Sundays on 2xx 98.3FM.
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