I am not sure how many Christians understand these things. Three hundred years ago, almost everyone understood their world in this way. Many people in Africa still think this way, although they focus to much on the dark side of the spiritual. Now, under the relentless pressure of education and the enlightenment, interest in the spiritual dimension of life is labelled old fashioned and superstitious.
I also wonder how many Christians understand these things, but do not live them. How many live as if the spiritual realms are irrelevant?
Many Christians are looking inward to establish connecting with the Holy Spirit. This is good, but if we ignore what is happening in the spiritual realms that surround us, we will misunderstand much of what happens in the world. Most Christians need a vastly expanded worldview.
The previous picture correctly shows how the spiritual and physical realms overlap each other. However, in the remainder of the article, I will place the spiritual realms just above the physical realms so that the interactions between them can be illustrated, but we must always remember that these two worlds overlap and exist in parallel to each other.
Multi-dimensional
The spiritual realms are not limited to three dimensions like our physical world. The Bible does not tell us how many more, but the fact that it is more complex than our three-dimension world means that it is hard for our minds to understand. The spiritual aspect of life can be thought of as additional dimensions beyond the three core dimensions of length, height and breadth. The spiritual world is not another world in another place, but additional dimensions to the physical world we observe.
An even better way might be to think of the physical world as three additional dimensions tacked on to a multi-dimension spiritual world. The spiritual world is more real than the physical world, so this latter view is most likely correct, but it is very hard for us to handle, because our eyes are calibrated for a physical world. Our eyes are so attuned to seeing a three-dimensional world, that we find anything grander difficult to conceive.
Paul visited the spiritual realms in a vision. He was dramatically affected by what he saw, but he could not describe it (2 Cor 12:2-4). His problem was that human language is designed for describing a physical world, so it cannot cope with spiritual reality. He explained that,
Eye has not seen, nor ear heard, and no human mind has conceived (1 Cor 2:9).
We need spiritual insight to understand what is happening in the spiritual dimension. That is why Paul prayed that the "eyes our hearts may be enlightened' (Eph 1:18).
Seeing Changed
Prior to the fall, Adam and Eve could see into the spiritual world. They were able to walk with God in the cool of the evenings and speak directly to him. They were able to see the devil, when he came to tempt them. His activity in the spiritual dimensions, made him appear snakelike from a physical perspective.
This situation did not last longs. When Adam and Eve sinned, their sight was changed so that they could no longer see into the spiritual realms.
The Bible says their eyes were opened, and they realized they were naked (Gen 3:7). This statement is a huge irony. Their eyes were actually closed to the spiritual realms. When they could see the brilliant glory of the heavenly realms, their observation of the physical world was dimmed, and they did not notice they were naked. Once the light of heavenly glory was turned off, their view of the physical world was greatly intensified, so they realised for the first time that they were naked.
After his death and resurrection, Jesus gained a spiritual body, which enabled him to interact more freely with the spiritual world. After death, those who believe in Jesus will be given new spiritual bodies.