What Is Dark Matter?
https://www.scientificamerican.com/article/what-is-dark-matter1/
Physicists and astronomers have determined that most of the material in the universe is “dark matter”—whose existence we infer from its gravitational effects but not through electromagnetic influences such as we find with ordinary, familiar matter. One of the simplest concepts in physics, dark matter can nonetheless be mystifying because of our human perspective. Each of us has five senses, all of which originate in electromagnetic interactions. Vision, for example, is based on our sensitivity to light: electromagnetic waves that lie within a specific range of frequencies. We can see the matter with which we are familiar because the atoms that make it up emit or absorb light. The electric charges carried by the electrons and protons in atoms are the reason we can see.
Matter is not necessarily composed of atoms, however. Most of it can be made of something entirely distinct. Matter is any material that interacts with gravity as normal matter does—becoming clumped into galaxies and galaxy clusters, for example.
Peak your interest for answers to this dark matter conundrum by reviewing an alternative theory of the universe from a more 4th dimensional perspective. This concept was previously approached in the book, 'The Evolutioning of Creation: Volume 2', copyrighted in 2011. As the predominant condition of the universe is a combination of dark energy and dark matter (i.e., massless matter or negative mass density), then the existence of our universe [or positive mass density] is more of an intrusion upon this norm. Such is it that positive density mass (i.e., baryonic mass) provides for a displacement effect, which is expressed as if the positive mass has intruded upon the inertial condition of the space-time continuum.
You can peak your interest for answers to this mystery from the perspective of the science fiction novel, 'Shadow-Forge Revelations'. As science fiction imitates science theory, this novel discusses how dark energy and dark matter interplays with the concept of the expanding universe from the inception of its creation.