"" 

Managing the nitrogen cycle is crirtical over the long term, especially considering that have yet to get our population under control! Assuming that we all want to eat, that is, and clothe ourselves, build, etc. with renewable, biological materials.

"" 

Energy is the thing to begin with, because energy is necessary for everything. I don't care how it's done, but cheaper energy means cheaper electricity, cheaper transportation, etc. In the long run, cheaper energy means cheaper everything, which means everything can be done easier. With regards to ethics, that is not an engineering challenge. Furthermore, man is inherently evil. We aren't going to all work together perfectly to solve all of the world's physical wants and needs. Far better to not waste time trying, and do what you can, with whom you can, when you can without worrying that you won't get everything done.

"" 

Avoiding death is a greater challenge than giving life Life lost cannot be repaid by money or watts. so, we must make sure that our nuclear plants are more reliable than our dogs. All the other engineering challenges are also very important as you may all agree, but it is better not to give life than to take lives. Nuclear terror, like its name says...

"" 

If we can get solar energy, at a lower cost than oil energy, we will achieve a cleaner and better preserved earth. That is our number one problem.

"" 

New sources of energy are the most important engineering challenge as without cheap energy the current economy will collapse. Once we do this, then we can work on the robots to do all our physical work for us : )

"" 

This list is almost perfect. It covers new available energy sources, clean drinkable water, maintaining the enviroment, and the future of health care. I just thing the nitrogen cycle should be higher on the list.

"" 

Many of these are wacko, and fail to recognize what is really important - clean air, drinkable water, available energy, sustainable environment, universal health care (available in all developed countries except the nutcase US). Fusion is pie in the sky. We already have a well engineered fusion power plant located a safe distance from major population centers - the sun, 150 million km away. It is highly appropriate to choose development of solar energy as the first priority, and education will bring down the birth rate. As to medicines, if you threw all the medicines in the world into the sea, more people would live longer and the fish would get sick. We need healthier food and less medicines, not more.

"" 

I feel providing access to clean water should be ahead of making solar energy economical and providing energy from fusion.

"" 

Providing access to clean water is of utmost importance because without it you lose much of the human endurance necessary to accomplish the other 13 grand challenges. Water is a non-renewable resource that must be conserved for all of humanity to have access to food and potable water and to curb disease that comes from undersanitation. Reducing the human misery that results in a lack of access to clean water is an activity that compels the highest virtue in mankind.

"" 

Science is really wonderfull. Both manīs self conscience is still better. It is true that the challenges listed are of the utmost importance. But, how about revovering the publicīs trust in the engineerīs reliability and fair honesty? Is ethics rebirth a challenge or just a vain hope? If we engineers, as leaders of the usage of the planetīs resource and the betterment of the living conditions of mankind, act ethically all the challenges can be met, since the wordls resources could be devoted to solving these issues. Also ethics could prevent much of the violence thst deviates most needed resources into violence and terrorism fighting. To attain ethics, the only way is a proper education , ethically lived.

"" 

I think that one of the most important challenges is teleportation.