new approach to how social intercourse for work, play and education can be achieved. This is an engineering challenge as well as a policy and challenge 4. Finally we need new approaches to personal mobility. It is not good enough to think only as far as electric vehicles. this will not solve the problems of road safety, congestion or entirely avoid carbon emissions. New engineering solutions are needed to the fundamntal human societal needs for movement. Mohan, Noida, India "" It would have given me too a great pleasure to setup the grand challenge ... but looks like I was born in a timeline where I have to execute the challenges rather than set them up [ As I am not old enough ] . While I accept the challanges and would try my best to do our seniors proud by executing them, howeever, I have one wish that I would have added to the list: Design a game for life on earth so that human do everything except kill each other. Thanks Mohan Ernest Goh, Singapore "" Item 1 (make solar energy economical)... This would make Item 2 (provide energy from fusion) and Item 3 (carbon sequestration) irrelevant. Low grade waste heat from Item 1 or from our daily activites can solve Item 5 (clean water) Item 6 (improve urban infrastructure): Key components of urban infrastructure are 1) electrical energy, 2) heating, 3) cooling, 4) clean water, 5) handling waste water. (4) and (5) can be a "pseudo closed