Ever since its discovery by Fritz Zwicky (California Institute of Technology) in 1933, scientists, philosophers, and laypeople have pondered: what is dark matter?

Let us start by delineating the nature of dark matter based on current scientific observations:

• It is not in the visible spectrum. We cannot see it. It does not absorb or emit electromagnetic radiation (i.e. light).
• It does not strongly interact with other forms of energy or matter.
• It does exhibit gravitational effects. For example, it can bend light via its gravitational effects similar to the way ordinary matter is able to bend light.
• It makes up about 95% of the matter in the universe.
• It is concentrated within galaxies and acts almost like glue holding all the stars together in a constant fixed orbit around the center of the galaxy.
• It is absent between galaxies.

The most popular theory of dark matter is that it is a slow-moving particle, which travels up to a tenth of the speed of light. Scientists call the mass associated with dark matter a “WIMP” (Weakly Interacting Massive Particle).

On the surface this would seem to be a reasonable theory, but two issues raise serious concern about the existence of the WIMP particle:

1. The Standard Model of particle physics does not predict the WIMP particle. The Standard Model is highly regarded as one of modern science’s most successful theories. Since the Standard Model does not predict a WIMP particle, we have a serious basis to question whether the WIMP particle exists.
2. All experiments to detect the WIMP particle have to date been unsuccessful, including considerable effort by Stanford University, University of Minnesota, and Fermilab.

In my book, Unraveling the Universe’s Mysteries, I suggest a new line of research and theoretical enquiry. I posit the theoretical understanding of dark matter lies in M-theory (the unified theory of all string theories). I am not suggesting we abandon our current research, but rather broaden it.

Consider these hypotheses.

• Dark matter is in one of the not spatial dimensions of M-theory: Since finding the WIMP particle has proved elusive, it may not reside in the typical three-dimensional space where we conduct our experiments. M-theory posits eleven dimensions. This opens up the possibility that the WIMP particle may reside in one of non-spatial dimensions predicted by M-theory.
• Dark matter is not a particle, but a quantum (discrete packet) of energy: Dark matter may not be a particle, but a quantum of energy. We know that mass and energy are equivalent from Einstein’s famous mass-energy equivalence equation, E = mc², where E is energy, m is mass, and c is the speed of light in a vacuum. This would also explain why the Standard Model does not predict the WIMP particle.

In my book, Unraveling the Universe’s Mysteries, I suggest experimental methods to determine the validity of the above hypotheses.

It is hard, if not impossible, to believe that most of the mass in the universe has eluded detection and may not be mass, but energy.

Welcome to the edge of science, where physics and metaphysics blurs.