I was on the American River, Paradise Beach, in Sacramento, CA. The river was cold, the beach sand was hot. I cupped both my hands together and scooped up as much hot sand is I could, then lowered the sand into the cold river. Almost instantly, the sand touching my hands became much, much hotter, almost too hot to hold. What explains this? Did the cold water concentrate the heat from the sand - against my skin?
It's due to relativity of our feelings. When our hands are in the warm air the the temperature difference between the air and sand is much smaller than the difference between the cold water and the sand; and we feel the sand much hotter in the water comparing to the air.&