1. xbmcuser’s point:
They challenge the anthropocentric (Earth-centric) assumption — “we only know life as we know it.” Philosophically valid, but scientifically weak without proposing a viable alternative chemistry.
2. joshuahedlund’s reply:
Grounds the argument in chemistry and probability.
There are only ~90 stable elements → a finite combinatorial chemistry space.
Among possible solvents, water is the most abundant and chemically versatile (dipolar, wide liquid range, high heat capacity, good at dissolving ions and organics).
→ So even if other solvents can work (like ammonia, methane, formamide), the odds heavily favor water-based life.
3. caymanjim’s addition:
Brings in carbon’s unique valence behavior:
4 valence electrons → can form stable, complex chains and rings.
Bonds are strong but not too strong → dynamic yet stable biochemistry.
Silicon (next best candidate) forms brittle, static lattices and poorly soluble oxides → bad for metabolism.
→ Therefore: if life is carbon-based, water is the only sensible solvent.
2. joshuahedlund’s reply: Grounds the argument in chemistry and probability.
There are only ~90 stable elements → a finite combinatorial chemistry space.
Among possible solvents, water is the most abundant and chemically versatile (dipolar, wide liquid range, high heat capacity, good at dissolving ions and organics). → So even if other solvents can work (like ammonia, methane, formamide), the odds heavily favor water-based life.
3. caymanjim’s addition: Brings in carbon’s unique valence behavior:
4 valence electrons → can form stable, complex chains and rings.
Bonds are strong but not too strong → dynamic yet stable biochemistry.
Silicon (next best candidate) forms brittle, static lattices and poorly soluble oxides → bad for metabolism. → Therefore: if life is carbon-based, water is the only sensible solvent.