Dark matter plus dark energy makes up over 90% of the matter in the universe, and science doesn’t understand the nature or either of them. Normal matter, the stuff we can typically see and touch, makes up only 5-10% of the matter of the universe. That means that science does not understand over 90% of what makes up the universe. In this article, I will confine my discussion to the 90% we don’t understand, dark matter/energy.

The most popular theory of dark matter is that it is a slow-moving particle. It travels up to a tenth of the speed of light. It neither emits nor scatters light. In other words, it is invisible. However, its effects are detectable, as I will explain below. Scientists call the mass associated with dark matter a “WIMP” (Weakly Interacting Massive Particle). Dark matter has a long history, that goes back to 1993. For purposes of brevity, I won’t delineate the history here. However, I want to point out that modern science believes that dark matter is the invisible glue that holds galaxies, like our Milky Way, together. It is an experimentally observed fact that the outer most stars in our galaxy are orbiting at the rate at the inner most stars. If the galaxies followed Newton’s law of gravity, the outermost stars would be thrown into space. This implies that either Newton’s laws do not apply, or that most of the mass of galaxies is invisible, hence the name dark matter. Even in the face of conflicting theories that attempt to explain the phenomena, most scientists believe dark matter is real. None of the conflicting theories (which typically attempted to modify how gravity behaves on the cosmic scale) is able to explain all the observed evidence, especially gravitational lensing (the way gravity bends light).

Currently, the scientific community believes that dark matter is real and abundant, making up as much as 90% of the mass of the universe. However, dark matter is still a mystery. For years, scientists have been working to find the WIMP particle to confirm dark matter’s existence. All efforts have been either unsuccessful or inconclusive.

The above is a brief thumbnail sketch of dark matter. Now, let’s discuss dark energy.

Mainstream science widely accepts the Big Bang as giving birth to our universe. Scientists knew from Hubble’s discovery in 1929 that the universe was expanding. Prior to 1998, scientific wisdom was that the expansion of the universe would gradually slow down, due to the force of gravity. However, in 1998, the High-z Supernova Search Team (an international cosmology collaboration) published a paper that shocked the scientific community. The paper was: Adam G. Riess et al. (Supernova Search Team) (1998). “Observational evidence from supernovae for an accelerating universe and a cosmological constant.” Astronomical J. 116 (3). They reported that the universe was doing the unthinkable. The expansion of the universe was not slowing down—in fact, it was accelerating.

Almost all scientists hold the paradigm of “cause and effect.” If it happens, something is causing it to happen. Things do not simply happen. They have a cause. Therefore, it is perfectly reasonable to believe something is countering the force of gravity, and causing the expansion to accelerate. What is it? No one knows. Science calls it “dark energy.”

That is the state of science as I write this article in April 2015. Galaxies should be flying apart, but they don’t. Science postulates that a slow-moving particle traveling up to a tenth of the speed of light that neither emits nor scatters light is responsible, and they call that particle “dark matter.” However, there is no solid theoretical or experimental evidence to support its existence. The universe’s expansion should be slowing down due to gravitational attraction, but instead it is accelerating. No one knows why. Scientists reason there must be a cause countering the pull of gravity. They name that cause “dark energy.”

Dark matter and dark energy have two things in common. They both have the word “dark” in their name and they are both a mystery to modern science.