What is the meaning of real life?

The half life of a given radioactive nuclide is 138.6 days. What is the mean life of this nuclide? After how much time will a given sample of this nuclide get reduced to only 12.5% of its initial value?

What is life span?

What is the life span of the ecosphere ?

What is the probability of a radioactive nucleus to survive one mean life?

What are the four stages of life?

What is functional unit of life ?

What was site of origin of life?