All the matter we know off whether it be light, or atoms consists of just under 5% of the total matter of the universe. The rest of matter is made up of about 75% dark energy and 25% dark matter both of which are invisible. If you think about this, you realize that what we experience is only a fraction of reality. Although we don’t have hard evidence for what they really are, we are pretty sure they exist.
Dark matter makes up most of the mass of galaxies and further galaxy clusters, it is also the reason why galaxies are organized the way they are. The gravity of normal matter is not strong enough to form galaxies and complex structures. Moreover, if there was no dark matter, stars would probably be scattered all over the universe and not form clusters. Although our knowledge is limited, we do know that it does not emit or reflect light and by observation, places with a high concentration of dark matter bend light passing nearby. We can infer that it is something that interacts with gravity.
There has been some speculation that dark matter is anti-matter, but this is false as anti-matter produces unique gamma rays when it reacts with normal matter.
Dark energy is even stranger. It is a form of energy that is proposed by physicists to explain why the universe is not just expanding but doing so at an accelerating rate. This is linked to a discovery made by the Hubble telescope in 1929: it was found that the wavelengths emitted by distant galaxies shifts towards the red end of the electromagnetic spectrum as we travel further into space. The red shift as it was later named is what tells us that the universe is expanding due to the stretched wavelengths between two planets.
Wherever there is empty space in the universe, it is expanding, a greater amount is forming every second. Dark energy is in turn, intrinsic to empty space, it is the strongest form of energy. To emphasize, if you took everything in the universe, it would still not account for the amount of energy empty space has.
There are a few theories surrounding dark energy:
-it is just a property of space
-empty space is full of temporary, virtual particles that spontaneously and continually form from nothing and disappear into nothing – energy from those particles could be dark energy
-unknown dynamic energy fluid or field which permeates the entire universe
It is important to note that these our still just theories and we do not have the ability to confirm or deny them just yet. However, in this expansive world of technology and science, you never know what we can find out.