(cross-posted at Kalilily Time)
Your eight-year old can't go to sleep because he's crying so hard. He's crying so hard because, he says, he doesn't want to ever die and he doesn't want anyone he knows to ever die because he doesn't want to be alone.
You don't really believe in "God," and don't believe in heaven. You're not religious, and the Golden Rule is about the closest you come to embracing any doctrine, although you try to pass along a moral and ethical code that you hope he understands and continues to live by.
But what about "after?" What about after this life? What do you tell your eight-year old that will calm his fears without outright lying?
What you do is write a book that explains who and what we are in a way that will address his fears yet still be in the realm of what might actually and scientifically happen. ( After all, Carl Sagan thought so.)
And you call this book Spark.
Go over online and read through Spark -- and see if it's the answer you're looking for.