Dark Matter does not interact with the Electromagnetic Force. This means it does not absorb, reflect, or emit light, making it extremely hard to spot.
Nevertheless, we know that Dark Matter and Dark Energy exist because if they didn’t, Universe would become a terribly weird and practically impossible place to exist as it does.
Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total mass–energy density or about 2.241×10⁻²⁷ kg/m³.
Dark energy is the mysterious force that’s causing the rate of expansion of our universe to accelerate over time, rather than to slow down.
Dark matter and dark energy are the yin and yang of the cosmos. Dark matter produces an attractive force (gravity), while dark energy produces a repulsive force (antigravity). Together, they make up 96 percent of the universe—and we can’t see either. Astronomers know dark matter exists because visible matter doesn’t have enough gravitational muster to hold galaxies together.
The evidence for dark energy is indirect but comes from three independent sources: Distance measurements and their relation to redshift, which suggest the universe has expanded more in the last half of its life.
Dark energy is unlike gravity in that it repels matter and therefore causes the expansion of the universe to accelerate. The first evidence for dark energy came from supernovae observations in 1998 and further evidence arrived earlier in 2002 from a survey of 250,000 galaxies.
And as for Dark Matter:
Imagine the Universe was a pie, and you were going to slice it up into tasty portions corresponding to what proportions are what. The largest portion of the pie, 68% would go to dark energy, that mysterious force accelerating the expansion of the Universe. 27% would go to dark matter, the mysterious matter that surrounds galaxies and only interacts through gravity. A mere 5% of this pie would go to regular normal matter, the stuff that stars, planets, gas, dust, and humans are made out of.
Considering it cannot be seen, felt or detected with any instrument available, one might wonder how do we know or how can we say it exists.
Well, if they don’t, then the Universe is made up of matter and energy much less then is required for its state of existence.
And if we start to think that the Universe is made up of only what we can see, well, then that would be too presumptuous of us considering that we would never be able to account for the entire energy and mass of the Universe, Stars, Nebulae, etc.
Dark Energy and Dark Matter aren’t anything magical or obnoxious like “Black Magic”, etc. These are simply termed Dark because we haven’t yet been able to detect them.
Considering the composition of Universe as we know it, and the amount of Matter and Energy we cannot perceive or detect, it is extremely possible that there might even exist stars and nebulae made completely of Dark Energy and Dark Matter, thus rendering them totally undetectable to us with our current equipment.