Text of the Tree of Life: http://dailyzohar.com/?page_id=5890
The creation of the empty space is called ‘Tzimtum’ and the literal meaning of this word is ‘reduction’. The Endless light reduced its presence in the sphere to make a place where his powers could be revealed.
The missing light created a state of darkness that is the root of the forces of judgments. The lack of light also created something that was never there before and it was the vessel.
Having something and experiencing lack creates a vessel, which is a desire to restore the light that was there before.
The benefit of this aspect of Creation is that now, we can have a drive to fulfill our vessels.
The sphere could not stay in the dark so in the next step, the Endless continued a thin line that is like a pipe from the Endless all the way down but it didn’t touch the other end of the sphere.
Why didn’t the line go all the way down?
The endless surrounds the sphere and if the line were to touch the other side it would have flooded the sphere with the Endless light and would have voided the existence of the sphere and its identity as a ‘vessel’.
If two elements become equal they are ‘merged’ into one and we can not see differences between them. Simple example is a cube of ice that comes in touch with water. Once the ice melts into the water, we can not see it anymore.