Emptiness isn’t a description of how the world is; it’s a description of a way of seeing and being, paradigmatically when we are meditating.
In the original Pali, it just meant absence. “This place is empty of elephants” just meant that no elephants are here, but the meaning changed with the Mahayana.
In the Heart Sutra, we chant “form is emptiness, emptiness is form”, “form” being the first of the five skandhas, but in the earliest of the prajnaparamita sutras, the formulation is different:
Form is not wisdom (prajna) and wisdom is not form.The Heart Sutra
Just as with feeling, perception, will and consciousness.
They are not wisdom and wisdom is not in them.
Wisdom is like space…
This is probably the origin of the widespread use of space/ the sky as a metaphor for emptiness, the dharmakaya, and lots more besides.
Space is “empty” because we can’t say that it either exists or doesn’t exist, and thus it becomes the exemplar of a new definition of emptiness, one where all the familiar dualities, good/bad, samsara/nirvana, delusion/enlightenment are “empty” because everything is “empty”. That is, everything arises within dependent origination.
The translation choice of “emptiness” for sunyata is unfortunate, as it suggests vacuity, nothingness, and ignores the connotations of the space metaphor: openness, freedom, brightness.
How is this relevant to our practice?
It seems to me that space/emptiness/prajna is a good description of our experience in zazen. When we are sitting, we don’t feel we are something solid, like a block of flesh, we feel spacious. It is as if we are hanging in space. In our breathing, we are, as it were, making this space dynamic: it is moving within us. Except, our actual experience isn’t of an outside and an inside, but an interrelation of the two, our airway the connecting channel between two oceans.