In the scientific universe, dark matter is one of the most mysterious and elusive concepts out there. Its very nature is cryptic and only the most advanced theorists and scientists can give even a vague but good understanding of what it might be. The key word in that sentence is “might.” Science is only best guess, so dark matter, being as hard to understand as the ultimate question of human existence, is probably one of the most intriguing theories out there; one that science is dying to get a hold of it. You’d also be surprised to see how many theories are involved with human existence. Dark matter is, and will be proven, to be directly tied into human existence. The problem is proving it.
There are a few things to clarify before dwelling into the realm of science, a beginner course if you would. Firstly, normal matter is what we see, smell and feel. It comprises the air, the sun and the earth. A star is a dense mass of gasses with an even denser core, which explodes after so many atoms combine and then becomes a black hole or a dense star known as a white or brown drawf. These stars are roughly the size of terrestrial (earthlike) planets. Gas clouds are left over remnants of supernovas, a star that burned through and combined its atoms so fast that it died violently. The last thing one needs to know in order to understand space is that dark matter, theoretically, fills in everything else in the universe. It’s invisible and vastly unknown.
Dark matter to many people, for those few who actually study it on a leisure perspective, is a constant force in the universe that is both hard to find and hard to measure. Explanations will be given later in this paper on how to measure and find it. The other pondering question that pops into people’s heads is the question of dark energy. What is it? When does it happen? Those are very good questions. Dark energy has three main theories. The first is that it is a property of space. It is still a mystery however but this theory states that, if correct, the universe will continue to create empty space and dark energy, never to stop expanding. The second theory is that space is full of “virtual” particles that continuously come into existence and then out. However, this theory hasn’t been correctly proven. Physicists were off by a few hundred zeros. The most dynamic and odd theory is that dark energy is a fluid or field that we cannot see. It would act as an opposing force to normal matter and energy in the expansion of our universe. This theory is also a mystery. (NASA)
The question of what dark matter is comes in two parts. One has to know that there are two forms of the invisible substance. The first type is cold dark matter. It is where the dark matter has mass larger than its counterpart ‘hot’ dark matter, which is nearly infinitely small, therefore causing it to move slow. The laws of physics dictate that it is cold then instead of hot. The second type is “hot” dark matter. It is when the particles of dark matter are moving nearly the speed of light, since it is almost massless. Because of this, it is hot, instead of cold (White).
The difference between the two is that one is moving very fast with a lot of pressure, just like boiling water, and the other is moving slow, like ice. (Garfinkle)
There are several theories on dark matter, one in particular relates to the expansion and creation of the universe. Therefore, it directly involves itself with the creation of human life and existence. This interesting and complex theory is that when the universe hadn’t been created yet, based only on the theory of one point of origin resulting in the Big Bang Theory, the universe was infinitely small but still had denser parts of dark matter inside of it -kind of like blue Swiss cheese-. This matter, when finally released with the big bang, was then scattered. When the matter was sent flying across the universe, the denser spots that were originally inside the origin started to gather the resulting gas clouds after a few billion years in dark matter halos. These gas clouds formed the galaxies we see today. Because dark matter has such a strong gravitational pull, as you’ll understand later as an undeniable fact, the gas clouds were attracted to it, since nothing can go against the laws of physics; it was only natural that these clouds formed enough stars to create a heavy mass near the center, then creating a supermassive black hole. Gravity from the black hole took over from there. The growth of dark matter halos provided stability for galaxies to form. It expanded space between stable structures like galaxies by tearing apart unbound structures (sources). That’s why the universe isn’t one massive galaxy and why singular gravitational anomalies – black holes – took over.
Interestingly enough, roughly 70 percent of the universe is made up of dark energy and twenty-five percent is made up of dark energy. The last five percent is composed of “normal” matter and energy. (NASA)
Galaxies contain mass that isn’t just the stars, a lot of it actually, which is why scientists are baffled. Most of a galaxy’s mass is measured in a mass to light ratio. In order to measure the mass of galaxies -as previously though- you have to measure the light. However, when scientists measured the light…it came out wrong, way wrong. So naturally, there were a few culprits that they immediately looked at though, for reasonable explanation. These culprits were categorized into two groups, MACHOS and WIMPs. The Machos are large mass objects and the Wimps are weak gravitational objects. Machos and wimps are mostly invisible so they seemed to be very good culprits of dark matter theory. The first Machos were black holes, gas clouds, and anything else with a heavy gravitational pull or large mass. Of course these were the easy targets. Black holes are everywhere and invisible, so they’re very hard to find. However, with gravitational lensing, a method found from bending light around a MACHO, they are detectible. Sadly, there are not enough of them to account for such a difference in mass to light. (Garfinkle)
A very likely culprit of why there was so much mass in a galaxy than light, was gas clouds. Yet, Science disproved this theory because gas clouds are remnants of stars and those stars were once made up of normal matter. Therefore, they cannot be dark matter.
Science seems to have one strong leading theory about dark matter being composed of “sterile neutrinos”. These particles are small, roughly of a few kiloelectronvolts (1 keV is a millionth of the mass of a hydrogen atom). While neutrinos, a particle that lurks around space and gets produced from our sun, might not compose much matter in the universe; science thinks that there is much more mass made up of sterile neutrinos. See, these particles can travel anywhere they want, deep space, solar systems, even inside the earth and back out again. There aren’t that many neutrinos, and even fewer that we can measure because they react with hydrogen atoms. This makes it very hard to find and measure them. (Max)
Neutrinos would be considered WIMPs because they are small and invisible. Other WIMPs include: Sterile neutrinos, photino, an uncharged large photon that acts weakly with matter; Axions, low mass particles that are less than a millionth of an electron in size. (Freudenrich)
In hindsight, observations of dark matter theory came back inconclusive. However, they did find some culprits completely absolved of the identity of dark matter.
Keep in mind that since there are so many theories on what dark matter could be and how it effects the universe, particularly the expansion, there is quite a bit of skepticism about it. Some say its black holes and neutrinos, and others say its antimatter and a new particle we haven’t discovered yet because we haven’t been looking hard enough. One thing is for certain though…a lot of people are anxious to find out what it is absolutely because it greatly affects our future. You see, the universe expands constantly but if there is too much dark energy in the universe, the universe will collapse. This could cause everything to dense down into one singularity. We don’t want that. Even if it is a few hundred billion years from now, that we can guess, we still don’t want to see the entire universe, everything we’ve yet to discover, collapse. Because of this, scientists are very excited to learn everything they can about dark matter. The challenge is basing all of that on best guess, which most of science is.
There is enough evidence to support the theory of dark matter as explained above. Skepticism on the matter-excuse the pun-, seems only to encourage science to pursue its study of dark matter and energy. Dark matter theory is widely accepted. As of this point, there is no other explanation for the difference in mass to light ratio of galaxies or the explanation of the void in space. It’s only realistic that there is a particle or fluid or even another element that has something to do with it. Dark matter theory is explainable, widely accepted, and supported. Therefore, it is present in our current view of the cosmological universe.
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Freudenrich, Ph.D., Craig. “How Dark Matter Works” 04 September 2007. HowStuffWorks.com. 29 March 2012.
Garfinkle, David; Richard. Three Steps To The Universe: from the Sun to Black Holes to the Mystery of Dark Matter. Chicago and London: The University of Chicago Press. 2008. Print
Max Planck Society. “Did ‘Dark Matter’ Create The First Stars?.” ScienceDaily, 19 Mar. 2006. Web. 29 Mar. 2012. .
White, Martin. “Dark Matter.” www.berkly.edu. Berkly, 4 Jan. 2009. Web. 28 Mar. 2012. .