why is the lunar eclipse not visible on all the places on the night side of the earth ?
please answer fast have a test tomorrow 

The lunar eclipse is fully visible if the sun, the earth and the moon are in total alignment and in that order. But if you are at a place not in the line of total alignment and still in the night part of the earth then it may happen that you see only a partial eclipse. But, if you are very far away from the line of alignment then you may not see it at all. 

This is because the shadow of the moon which is formed due to the eclipse is in the shape of a cone and as you move farther away from the tip of the cone the area of eclipse gets shorter and shorter and when you are too large a distance apart then the tip for you vanishes and you are not able to see the shadow and hence the eclipse.