I remember for years Christians & other spiritually-minded people would talk about there being a 'fifth dimension' beyond the four we know, length, depth, height & time. It was called the fifth dimension & you generally had to be religious to believe that there were any more dimensions than the ones that make up the physical time-space fabric we know.
Now String Theory has been fully developed by serious scientists & they're saying that there are ELEVEN dimensions to account for all the effects we know & to answer questions like, 'Why is gravity so weak compared to other forces?' They talk about our physical universe sitting on top of a membrane (called a brane for short) in other dimensions & apparently this theory of eleven dimensions has moved off the chalkboard into mainstream acceptance.
I clearly don't understand the math but am interested in the fact that serious scientists now postulate so many dimensions when only a few decades ago a person was considered unrealistic to insist there might be five dimensions. Lots of room for spiritual beings & planes to exist now.
I don't believe in spiritual 'matter' as wispy, non-material stuff, butas a kind of matter beyond our four-dimensional plane. It just happens to be beyond the ability of our present senses & instruments to detect.