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accepted Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
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revised Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
added extra thought about freezing water in anti-gravity
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comment Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
When all water temperatures are greater than 4°C, my inequality applies. When all water temperatures are less than 4°C, your inequality applies. There is no apparent middle ground in these inequalities that explains temperature ranges that extend both above and below 4°C.
May
8
comment Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
Thanks for tracking down some empirical data. It just about convinces me that my idea is basically right. I had not considered the ground at the bottom of the lake as a heat source, but it appears to be acting as one.
May
8
comment Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
I agree with your temperature ranges, and I assume something similar exists when the temperature is on the other side of 4°C, where 4°C <= Tbottom < Ttop. If you look at these inequalities together, you'll note that the order of Tbottom and Ttop inverts on opposite sides of 4°C. The only way to reconcile these two inequalities is for there to be a state of the lake where temperature is 4°C throughout.
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revised Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
edited body
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asked Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?