There are some definitions and theory already had been provided by great physicians.
Scientist, Business Development Consultant, Bangladesh
According to Albert Einstein separation of present, past and future all are illusion. But the separation is very convincing which means past, present and future division is there but could not be identified by him. It kept beyond of his thinking level. But he made us clear that time is a one thing. And it’s not possible to identify the separation neither any one can relate present, past or future as well. So what do you think? It’s not possible to define time? Or it will remain as illusion of what is present, what is past and what is future? Let’s see the definition of time in next chapters. And check out the relations between past, present and future in mathematical formula in later chapters. After reading the whole thing you will get the proof that Mr. Albert Einstein was not correct now any more. Because, present is equal to the summation of past and future although that has no value for human. The assumption is same as a book of a journal or ledger accounts. It had to make the balance equal and the result should be the “Zero” all the time thus is the present had to be the “zero” of the summation of past and future as per the logic of nature. This “Present” is that “Life of world” referred and meant by the prophets and religious people. Not only that we shall become confirm that we are coming from future and going towards the direction of past.