what is the "density" exactly means?

[0lin]

This statement has never made any sense to me:

As the green-ray cycle or the density of love and understanding begins to take shape the yellow-ray plane or Earth which you now enjoy in your dance will cease to be inhabited for some period of your space/time as the space/time necessary for fourth-density entities to learn their ability to shield their density from that of third is learned.

I think the only way to explain this is to consider "density" as not only our concept of density but also different planes or "parallel spaces". One density exist in one plane, but the planes are not parallel. They are crossing over each other forming a multi-dimension space. Theoretically, we can see, touch every plane of every density, but planes of densities over 3rd were shield by light. Or maybe we just misunderstanding Dewey B. Larson theory suggested by Ra.