This was one energy solution US Energy Secretary Steven Chu had no clue about. A Nobel Prize-winning physicist, Chu had just completed making an elaborate presentation at IIT Delhi on futuristic energy scenarios recently when a middle-aged man from the audience sought his views on an alternative source of energy — that from the muscles of cattle. The person said the cattle population in India was about 200 million and if these were employed to work turbines, the resulting electricity would be sufficient to cater to the demand of the entire country. A puzzled Chu first tried to make sure he had heard it right, then wondered whether this would not amount to going back in time. When the questioner insisted that this could be a viable zero-carbon option to produce electricity, Chu gave in and admitted that the thought had not crossed his mind and therefore he was not in a position to comment.