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Dark Matter



Dark matter is believed to make up approximately 27% of the known universe. However the magnitude of this estimation cannot fully be understood unless one also understands that all matter familiar to humans makes up only about 5%. This is one of the many realizations that tell us how profoundly little we know about the universe we live in.

But what is dark matter? For many its name conjures up thoughts of deep space and sci-fi movies, and in reality, no one can really be sure whether or not those images are accurate.

Dark matter is characterized by its inability to be detected by any of the human senses. This is due to its lack of electromagnetic interaction, i.e. it cannot or does not reflect, give off, or absorb light. Granted no one has ever attempted to taste or smell dark matter, but so far everyone seems accept the fact that it is for the most part imperceptible.

With the knowledge that dark matter itself it imperceptible to humans, it is impossible not to wonder how exactly scientists know of its existence. First, dark matter's existence is said to be "inferred." While this word may provoke connotations of uncertainty, the vast majority of specialists are reasonably certain of its existence. Their confidence comes from dark matter's gravitational influences throughout the universe, which are highly inexplicable without the inference.

Essentially, scientists observe dark matter through galaxies that rotate at rates that are highly unsustainable by their orbital axis/center of gravity. To use an analogy, this would be like earth revolving around the sun at a rate three times its normal speed, despite the sun's gravitational limitations. If the Earth were to increase its orbital speed drastically, the sun's gravity would no longer be able to sustain Earth's orbit due the principle of Newton's second law applied to rotation: F=mv^2/R. After using this same principle in certain other galaxies, scientists noticed that certain planets were moving far too fast to be held in orbit by the gravitational force of their suns, which as we know is equal to Gm1m2/r^2. The model below shows how the calculated velocities did not match those that were observed.

Image result for dark matter



This realization led scientists to delve deep into the fundamentals of physics, only to come to the conclusion that the gravitational pull of an unknown substance must be acting on these planets to keep them in orbit. Thus dark matter was inferred and research and new breakthroughs continue to be made about it today.


https://home.cern/about/physics/dark-matter
https://www.space.com/20930-dark-matter.html
https://www.scientificamerican.com/article/what-is-dark-matter1/
https://www.popsci.com/sites/popsci.com/files/styles/1000_1x_/public/import/2013/images/2011/12/Rotationcurve_3.jpeg?itok=ltCRS7yQ

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