Don't give up so easy. That triple point line looks a little thick to me.

That graph just tells me that water can not stay liquid at that press./temp. point. However, "pressure" is an average kind-a-thing as to what the molecules are doing. For a tiny instant some liquid, in my limited thinking, could come and go but not stay. A better understanding of enthalpy would probably help us both here.

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Lighten up! This is a stellar board!