A good example is the fact that we are unaware of the huge amounts of “information” that surrounds us. There are hundreds and thousands of radio and television signals in a major city. We cannot see or hear any of those programs (i.e., we are unaware of their existence) without having a radio or a television “tuned” to the correct frequency.

In the same way, we are unaware of the existence of 29 of the 31 realms centered around the Earth. Living beings in some of those realms live side-by-side by us, but we are unaware of them. Most of these beings have bodies “more like energy forms” than solid bodies.

With better detection technologies, we may be able to communicate with some of these living beings with subtle bodies in the future. Of course, those who develop abhiññā powers can also see some of them. We will get back to this issue below, but let us first discuss the relative locations of the 31 realms.
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That is why the realities out there are much more different than what we perceive with our very crude sense faculties. All the atoms and molecules in our bodies are in constant motion, not to mention the spins and rotations of uncountable suddhāṭṭhaka that constitute them.
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Now we know that there are billions of living beings in the body of a human being. See, “There are as many creatures on your body as there are people on Earth!“.

Hopefully, new technologies will enable us to “see” many living beings belonging to the preta, asura, and deva realms — as well as gandhabbā — in the future.