If heaven is facing the earth, I am at the back of heaven.  
The ocean floor is not as far as heaven,  
so if I were there, I would be easily discovered.  
So probably not.

I am one. You can count me easily.  
I am "A". You can read me silently.  
I am a star that can't twinkle.  
I am in the rain, but once it dries, I'm gone.

You can't compare me to animals, because their lives have purpose:  
Ants collect their own food day and night.  
Carabaos are black, but are called the farmer's wife.  
Hens protect their eggs.  
Not dogs, who are humans' best friends.  
Not cats, that hunt rats.  
And not even larvae, because in the end they become beautiful butterflies.  
Most of all, not birds that can fly between heaven and earth.

I am unknown.  
I write when I'm sad.  
I read when I'm problematic.