Sorry, Feynman... That second one differed from the Hobbit one (as noted earlier in the thread, you must have missed it)... The Hobbit answer was Mountains as you recall, while the answer to this one was iceburgs... Mountains (unless snow covered) do not generally melt in sunlight... ;^)
Could be argued that wind, rain and other forms of weather could 'melt' them though I suppose...
