Dark Matter
All the matter that makes up every star, planet and dust cloud in the universe only composes close to 5 percent of all matter in the universe. What makes up the remaining 95 percent? 25 percent of all matter in the universe is in dark matter, while the remaining 70 percent is dark energy. What is Dark Matter and why does it make up so much of the matter in the universe? Beyond that, how do we even know it exists? Dark Matter is an enigma, but that doesn’t mean that Dark Matter doesn’t have a major impact on the universe. There are numerous occurrences that show the evidence of Dark Matter
What is Dark matter?
Dark Matter is a form of matter that is undetected, emitting little to no light. The reason we call Dark Matter “Dark,” is because Dark Matter consists of a completely unknown form of energy. Dark Matter was first proposed by Zwicky in 1933, he used it to understand the, “Large velocities of individual galaxies in the Coma Berenices cluster.”[1] There is not a definite answer to what Dark Matter is, but we can theoretically assume what it could potentially be, such as Weakly Interacting Massive Particles. All we know as of right now is that Dark Matter does exist.
Evidence of Dark Matter
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Evidence for Dark Matter
In Spiral galaxies, such as the Milky Way, we can observe that unlike most objects orbital velocity, the orbital speed of spiral galaxies increase as it gets further away from the center of the galaxy and becomes constant once it is far from its center. From the orbital velocity equation (below) we see that the further away from the center of the galaxy, the slower the orbital velocity should be due to the radius. However, the galaxy is moving at a faster pace the further out, this means that the mass of the galaxy must be getting larger in order to counteract the increased radius. This gives us evidence that dark matter must exist as the matter of the spiral galaxy should not make the orbital velocity increase. Thus dark matter must be interacting with the spiral galaxy to speed up the rotation of the galaxy.
Another event which showed evidence of dark matter was when Nasa’s X-ray observatory took an image of two galaxies colliding, this collision caused dark matter to get separated from regular matter. The separation occurred because the collision caused regular matter to be slowed down while the Dark Matter moved at the same pace. The result is the following image.
PC: ASA/CXC/M. Weiss - Chandra X-Ray Observatory: 1E 0657-56
Dark Matter and formation of the Universe.
The reason why stars and galaxies are not uniform and appear very sporadically across the night sky is due to Dark Matter. When the Universe was first forming, it was, “homogeneous and isotropic.”[2] Meaning that all matter was equally distributed, but due to fluctuations within the universe, gravity soon pulled matter and dark matter together. These sections clustered together and eventually formed what will become galaxies. The evidence for this formation is through the Cosmic Microwave Background, where we see areas which appear hotter these areas are theorized to be the areas where dark matter and matter first interacted to form galaxies.
Chandra X-rayVideohttp://www.forbes.com/sites/startswithabang/2016/09/19/dark-matter-proved-real-by-colliding-galaxy-clusters/#6bcc722826be
https://www.youtube.com/watch?v=VGdk6QQN6LY
Sources:
www.jstor.org/stable/1353848.
[1] Moore, Ben. “Dark Matter.” Philosophical Transactions: Mathematical, Physical and Engineering Sciences, vol. 357, no. 1763, 1999, pp. 3259–3276. www.jstor.org/stable/1353848.
[2] Tuttle, Kelen. "When space expanded faster than light." EarthSky. Last modified February 16, 2015. Accessed 12/13/2016. http://earthsky.org/space/when-space-expanded-faster-than-light.
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