What is dark matter and dark energy? Well, no one knows. All we know is what we know of the universe – clouds, planets, stars, and the like – make up only about five percent of the full universe. The rest is seventy percent dark energy and twenty-five percent dark matter. Dark matter and dark energy are two different things, yet they are the same in that we do not know exactly what they are. We just know what they are not.
The universe only exists because dark matter is what makes it possible for the universe to exist. Because there was not enough of what we call “regular” matter, and because its gravity was too strong to form galaxies and the like, this is where dark matter came in and completed the job of forming galaxies and other complex structures. Dark matter does not emit or reflect light. Places with a high concentration of dark matter bend passing light, leading us to know that dark matter must interact with gravity somehow. We only know three things for sure about dark matter. We know that there is something out there, that it interacts with gravity, and that there is a ton of it.
Though we do not know what dark matter is, we can eliminate a number of things that it could be. We know that dark matter is not patches of clouds of normal matter without stars because it does not emit particles that we can detect. Also, it cannot be anti-matter, because then it would emit gamma rays that react uniquely when they interact with “regular” matter. Dark matter also cannot be made up of black holes, because if it were, then it would affect its surroundings in noticeable ways in which it has not.
Dark energy is an even bigger mystery. According to scientists, we cannot detect it, measure it, or taste it. However, it has clear effects. In 1929, during an experiment, Edward Hubble detected that light from farther, fainter galaxies emitted light more towards the red end of the light spectrum than nearer galaxies. He figured that this was because the universe was expanding and that the red light happens because when the universe expands, the wavelengths of light expand along with it. Recent discoveries have shown that the universe is constantly expanding, and that its expansion rate is quickening. Because space doesn’t change its properties as it expands, it needs to find a way to fill in the new space from expansion, and that is why there is dark energy. Basically, wherever in the universe there is empty space, there is dark energy, which is the strongest thing we know and keeps getting stronger as time goes on.
There are many theories as to what dark energy is. One of these is that dark energy is not a “thing,” but, rather, just a property of space, a filler-in for the emptiness. It can be empty space. Another theory is that dark energy is a part of space that continuously forms from nothing then gets deleted back into nothing.
The fact that we do not know what dark matter and energy are shows us that although we think we know a lot about space, there is still much to know. We know less than what we don’t know, and maybe someday, our descendants will look back at our time as a dark age because we knew so little about the universe.
Source: https://www.youtube.com/watch?v=QAa2O_8wBUQ
