| 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. |