Original: During British Mount Everest Expedition 1924 , the third British attempt on the world 's highest mountain , Mallory and his climbing partner Andrew Irvine both disappeared somewhere high on the North-East ridge during their attempt to make the first ascent or descent of the world 's highest mountain .
Simplified: with the reply : '' Because its there '' , which has been described as '' the most famous three words in the history of mountaineering '' .