Observations of stellar movements indicate that they turn too fast and that galaxies themselves spin and move faster than predicted. Gravity produced by visible matter in the universe is not enough to explain what holds the stars and galaxies together. There must be some unknown, non-luminous hidden force.
What makes the pin of a compass to point north? While we can’t see the force behind the spinning (magnetic field) we see its effect on the pin. Likewise, we observe certain phenomena in the cosmos whose origin is invisible and unknown. Dark matter is an invisible force that, until now, no one has been able to confirm.
Three Things we Know About Dark Matter
- We Cannot Observe it, but we can Observe its Effects: The extreme speed at which galaxies spin around themselves and in clusters can only be explained by a source of gravitation five times greater than that of visible matter. Hence the suggestion of dark matter or an invisible force imprisoning the visible matter in its mesh.
- Dark Matter is Ubiquitous: We know that dark matter is here, there, and everywhere. We know that it accounts for about 85% of the gravity of the universe. The baryonic matter that constitutes all the visible matter represents only 5% of the observable Universe, while 27% must be dark matter.
- We Know More About What it is not Than What it is: Dark matter probably consists of elementary particles but exists in no case of Byronic “normal” matter (protons, neutrons, and electrons). These supersymmetric particles might be light enough to pass through the detectors without being detected.
Three Things we do not Know About Dark Matter
- What is it made of exactly? Some theories evoke the existence of a “hidden valley or sector.” This is a parallel world where dark matter particles reign, having nothing in common with particles with which we are familiar.
- Does Dark Matter Interact With Other Forces? Until today, it’s commonly accepted that only gravity seems to act on dark matter. But a team of researchers showed that after a gigantic collision, dark matter followed a galaxy with a delay of 5000 light-years. The friction caused by the collision may have slowed down the dark matter.
- Could There be Dark Antimatter? According to the principle of charge conservation, the creation of a particle of matter must be accompanied by an antimatter particle. Can we say the same about dark matter? Could there be dark antimatter?
Between what we know about dark matter and what eludes our understanding, it’s obvious that we’re just scratching the surface of the unknown.
Some experts, like Eric Verlinde, deny the existence of dark matter and think the concept was invented to plug the holes in our knowledge and explain the discrepancy between our understanding of the accelerating expansion of the universe’s visible matter.