Ordinary hydrogen is sometimes called a perfect fuel because of its almost unlimited supply on Earth, and when it burns, harmless water is the product of the combustion. So why don’t we abandon...

Ordinary hydrogen is sometimes called a perfect fuel because of its almost unlimited supply on Earth, and when it burns, harmless water is the product of the combustion. So why don’t we abandon fission energy and fusion energy, not to mention fossil-fuel energy, and just use hydrogen?