Why does God call the firmament Heaven?
The firmament is the present, where the laws of Heaven are always present. In the present, every law is always in effect.
For the Human, the experience of the world takes place in time, because knowing the world in its details is only possible if our perception is limited in both time and space.
We are only capable of imagining the past and the future, but within our imagination only those laws are in effect that we already know. The past and the future always reflect what we already know.
The present, however, does not depend on our knowledge. Reality is influenced by all the laws of Heaven, regardless of whether we know them or not.
We consider the future to be fluid because our knowledge is constantly changing. Through our experiences, we continuously develop, learn, or recognize our false interpretations within them, but this, too, is part of learning. The future appears to take shape and change because our knowledge changes, and with every change we imagine differently what is yet to come.
The past appears to be fixed, but in reality we continuously re-evaluate the events that have already taken place as our knowledge changes. The past is also transformed according to our knowledge into a form that we are currently capable of interpreting.
We are only capable of interpreting the present according to our current knowledge, and because we do not know every law that influences the world in the present, our will also appears—we want to change what exists. Thus, Heaven is truly present in the present, because all the laws of Heaven are at work there, yet we can perceive only as much of the present as our current knowledge allows.
God called the present Heaven because if we do not evaluate what we experience, we become capable of perceiving more and more of what is—of what exists. The laws of God become recognizable when we seek not to change the reality we experience, but to understand it.
"The Kingdom of Heaven is here." It is always here and now, both in time and in place.