What do I mean by this statement “upper & lower worlds”, I am talking about the lower worlds of Malkuth; the material realm we exist in and the upperworlds of the Tree of Life these are the emotional states of being leading to the holy chambers upon high for which we strive to reach .
We must also consider thefact there are worlds within worlds and trees within trees. Each Tree of Life has its own Tree of Life, so in Malkuth we have another tree, another Malkuth ad-finitum with all the sephirah.
Therefore;Malkuth becomes the Kether of a lower world as Kether becomes a Malkuth of a higher world.
Think of these worlds existing in the same space but existing on progressively higher and lower frequencies. All are interconnected and all come forth from the breath of God.
Every action creates a reaction if we study the Emerald Tablet of Hermes it clearly points the way “as above so below”. Scientists have recently discovered “string theory” and sub atomic particles. Based upon the theories of Albert Einstein they have “discovered” (or is that re-discovered ?) that the universe is made up of ten realms of existence (note the tree of life’s ten spheres). Furthermore the most recent discovery known as “M” theory has discovered an eleventh realm(note DAATH the hidden sephirah on the Tree of Life is the eleventh).
They believe that these eleven realms co-exist in the same space continuum but co-exist at slightly different time frames. Therefore there is a conscious level of perception that exists in eleven different spaces but at almost the same time!
By this analogy can you see how there are “worlds within worlds” and how to quote a famous text “there is no empty space”.
Imagine your existence as it is in the here and now in the time consciousness your soul is aware of. Now imagine another you, and another and another each existing but unaware of the other, each living out a different time continuum. Then ponder on the nature of re-incarnation and life after death. Meditate on this very deep subject and even on de ja vu I am sure it will provide answers for you on the nature of the universe and existence as we know it.
Each day science moves the boundaries discovering more about our universe and our very existence. One day both science and spirituality will merge into a whole new philosophy. Einstein’s unified field theory and his theory of relativity may shed light on your path.