by Karina Bakshi
Though learning about the universe sometimes seems overwhelming, there is actually a lot that we don’t know. Only 5% of the universe is composed of “normal” matter (the stuff we see). The rest of it is composed of dark matter and dark energy. But what exactly are these substances?
We know that they exist because of various scientific discoveries and observations such as unknown forces and invisible matter that we know aren’t ones we already know about. There is an unknown force that is pulling our universe apart and expanding it at an accelerating rate. This is what is called dark energy.
There is another type of unidentified force (besides gravity) that is keeping galaxies bound together. In a lot of galaxies, the mass of the stars, planets, black holes, and other matter just isn’t enough to keep itself bound together on its own. We cannot just dismiss this as gravity because gravity is too weak to do this all by itself. Instead, scientists have come to the conclusion that there has to be an invisible matter that is holding everything together with gravity. That matter is called dark matter. According to NASA, 68% of the universe is dark energy, 27% is dark matter, and only 5% is the matter we see!
A theory made by scientists regarding dark energy is that it is a dynamic energy, fluid, or field that fills space and has an effect on the expansion of the universe which is the opposite of gravity and normal matter. This is called “quintessence” by many scientists but we still have no idea what this is or why it’s here so there’s not much to say.
We know that dark matter is invisible matter because we cannot see it. We know that dark matter is not just dark clouds of regular matter because we cannot detect baryonic clouds (normal matter is made out of baryons). It isn’t antimatter either because it doesn’t give off gamma-ray signals when matter and antimatter particles annihilate each other (they annihilate each other because antimatter is matter but the particles in them have opposite charges). Another possibility is that it could just be huge black holes but that doesn’t make sense either because of the amount of gravitational lenses we see. It is likely that dark matter is made out of non-baryonic particles such as axions or Weakly Interacting Massive Particles (WIMPS).
Despite all of the discoveries we have made so far, we still know such little about dark matter and energy. Hopefully, we will learn more about them in the future but for now they remain a mystery.