What source of electrical energy have scientists been unable to use?

Fusion has powered the sun for billions of years.Yet despite decades of effort, scientists and engineers have been unable to generate sustained nuclear fusion here on Earth. In fact, it's long been joked that fusion is 50 years away, and will always be.

it is stable as it is in group 0 which have full outer shells of electrons

metric time was an attempt to create a standard unit of time based off of 10, but it never took off an is not included in the metric system (si)