What is life? Scientists redefine it as information and planetary process
Instead of a checklist, Adam Frank describes life as something that happens to a whole planet, and Sara Walker and Lee Cronin define it by how information and selection build complex objects. The shift matters because the definition decides what we look for on other worlds.
What is the textbook definition of life that these scientists reject? Show answer
A checklist of properties: metabolism, reproduction, a cell membrane and Darwinian evolution.
What does Adam Frank mean by saying life happens to a planet? Show answer
Life co-evolves with a planet's geology and atmosphere, so you must consider the whole planet and its history, not just a warm pond.
What does Frank call the true unit of life? Show answer
The biosphere, not DNA and not a cell.
How can astronomers look for life without knowing its chemistry, according to Frank? Show answer
By measuring how far an atmosphere is from equilibrium; a wildly unbalanced one suggests something is pumping gases in.
Why are oxygen and methane together a classic sign of life? Show answer
They react away quickly, so finding both means something, such as life, keeps replenishing them.
How does Sara Walker define life? Show answer
As the process of how information structures matter over time and space, with any individual being an instance of lineages structured across time.
Why does Walker say life is not self-sustaining? Show answer
Nothing is self-sustaining; humans, for example, depend on societies.
What is the assembly index in assembly theory? Show answer
The minimum number of steps needed to rebuild an object from its basic parts, where anything already built can be reused.
Why does copy number matter in Lee Cronin's theory? Show answer
One complex molecule could be a fluke, but many identical copies of a complex object could never arise by chance, so something must have built them.
What did Cronin's lab test with NASA samples find? Show answer
Biological samples produced molecules with an assembly index above 15 while abiotic ones stayed below, and NASA confirmed the calls were right.
How do Frank and Walker differ on equilibrium? Show answer
Frank uses disequilibrium as a sign for detecting life, while Walker says non-equilibrium physics and entropy are the wrong approach to explaining what life is.
What is Cronin's biggest fear about alien life? Show answer
That life is everywhere but each planet's history is so different that we never overlap with it, leaving us more lonely.