Modern Physics was a physics revolution in the 20th century filled with mysteries that perplexed physicists about our universe’s properties and types of matter, or substances. Theories were formulated about our universe’s matter in particular, but most models failed to represent this due to the lack of mass. Astrophysicists, astronomers, and physicists were disconcerted by this fact, which lead to calling the extra mass “Dark Matter.” These scientists have been building upon theoretical proofs, improving telescopes, and performing various experiments to prove their stance that the universe contains more mass than what the eye can see through Dark Matter. Dark Matter exists and is a valid theory due to the theoretical calculations, matching speculations, and various experiments that detected forms of Dark Matter.
The first theoretical calculations and theories about Dark Matter came up with Dutchman Jacobus Kapteyn. In 1922, Kapteyn created a model of galaxies where it a flat model, meaning that it was two dimensional. When he read Lord Kelvin’s estimations and observations of stellar velocities, suggested directly that dark matter existed, noting that the size and mass did not correlate. In Hooper and Silk’s article about theoretical Dark Matter, Kapteyn states that“The density of the stars were then calculated and noted that the density was too great for a star, addressing the status of Dark Matter.” Jan Oort, a fellow Dutchman, was studying stellar motions in local galaxies in 1932. He found that the mass in the gravitational plane was too great, but it was proved to be erroneous. But using that large mass, he assumed that there was something to it; it had mass and humans could not possibly see the mass, whether through a telescope or by the naked eye, affirming what Kapteyn had published. That lead to Oort’s conclusion of Dark Matter, saying that there is a possibility of its existence. Years passed, and in 1933, Fritz Zwicky, a Swiss astrophysicist studying at Caltech, was observing galactic clusters and also deduced that there was something called “Dark Matter” in the universe. It was because measurement that he obtained from theoretical calculations of the galactic mass via “its motions and brightness was about 400 times greater than the mass that was able to be measured visually” (Turner 6). It matched what Oort had said about galaxies in our universe.
At this point in time, technology was significantly primitive, deducing that these astrophysicists used basic telescopes to make notional computations, meaning that there was plenty of error to be examined if a possible experiment could be produced. However, the people who were in the field at this time couldn’t have conducted experiments for the technology was rudimentary. For example, baryon detection wasn’t possible until particle accelerators could achieve speeds that are in space, which was circa 1950s, and infrared along with other spectrum telescopes weren’t invented until the sixties. Despite this, these fellow scientists’ theories were able to corroborate with each other, establishing a base that Dark Matter existed, regardless of the temperamental base data computed by earlier methods.
The experiments commenced after Vera Rubin and Kent Ford precisely confirmed that the clusters contained a great amount of mass. According to Bertone, Hooper, and Silk in “Particle Dark Matter: Evidence, Candidates, and Constraints”, by using a spectrometer and galaxy rotation curves, Rubin and Ford collected data about the mass, and it was the first experiment that was conducted to measure the mass of clusters. This was accurate proof that qualified the theories produced by Oort, Kapteyn, and Zwicky on Dark Matter.
After this breakthrough, many astrophysicists and physicists began running experiments to prove the validity of the theory. One experiment by Clowe et al showed that Dark Matter existed through cosmic shears in the form of plasma and galaxy clusters. The temperatures of the measured objects were cold, almost close to zero Kelvin. Despite this, the detection of that was shown through gravitational lensing maps, stating that the distribution of the galaxy was massive. This deduced to the experimenters that Dark Matter filled up the rest of the volume within the gravitational potential. Dark Matter that was detected did not follow alternate gravity, but instead was almost segregated from plain matter within the collision, which was an interesting property. Milgrom, quoted by the authors in the article, said that modified Newtonian dynamics would not allow for Dark Matter to converge to the ratio of 7 to 1 K, implying that Dark Matter wouldn’t be ubiquitous in the cluster.
Moore et al conducted an experiment that used galactic halos to find Dark Matter. This experiment was to show that Dark Matter substructure tended to exist within the galactic halo of the cluster. The detection allowed the baryons of Dark Matter to be traced in “cold conditions.” This meant that it was the remains of dark matter from before and during the Big Bang and that finding proof of dark matter being most of the matter in the universe depended on finding Cold Dark Matter. Baryons are particles that hold up mass and can be any sort of matter, and in this case, axions and neutralino effects were detected to prove the existence of dark matter. Using a dinosaur analogy, like finding the first set of dinosaur fossils was extremely difficult and depended on chance, finding evidence for the baryons at galactic halos was immensely difficult. Once these researchers isolated the parameters and finally detected these particles (axions and neutralinos), they analyzed the properties in order to validate the theories that speculated about the particles. Moore et al noted something different, saying “ [the particles] are far from smooth; furthermore, the particle velocities in a single-resolution element have a discrete component that results from the coherent streams of particles tidally stripped from individual dark matter halos” (page 4). This meant that the neutralinos were annihilated, or destroyed, in the cores of the halos, reacting in a whole new way compared to predicted models. This not only proved that Dark Matter existed through baryons annihilating, but that its original form acted different from what humans predicted, raising more questions.
WIMP particles show the Dark Matter the best, with it being direct evidence. Found through Large Underground Xenon Experiment in the Sanford Underground Laboratory, these particles were a new set of fundamental particles. WIMPS are at the core of halos, producing a nuclear elastic scattering effect, producing energy of a few keV. That energy allows for detection to occur, with it being proof that they hold as direct evidence of the specific type of particle representing Dark Matter. However, it does not follow the allocated principles of gravity and relativity, raising suspicion about the theory of Dark Matter. Erik Verlinde at the University of Amsterdam disagreed with the theory. It is because the WIMPs (weakly interactive massive particle) depends on the MOND (modified Newtonian Dynamics), which is a totally different standpoint from Einstein’s General Relativity. In his published paper “Emergent Gravity in the Dark Universe,” he notes that Dark Matter cannot possibly exist without breaking the Standard Model, the foundations of Relativistic physics, and the theory of gravity. This means that most of modern physics’ principles become shattered by the existence of the Dark Matter and the particles’ properties. However, relativity doesn’t become broken, because Dark Matter is a completely different thing that isn’t affected by relativistic principles due to its nature of the particles. According to Bergstrom, Ullio, and Buckley in the paper by Bertone et al, Gravity also doesn’t affect the particles because the particles such as axions and WIMPs has such oblique forms of supersymmetry. Also, WIMPs interact exclusively through weak amounts of gravity and greater in weak force in addition to being a stretch in the Standard Model (the theory of fundamental particles). Likewise, WIMPs are not conventional particles and are affected differently from standard forces such as gravity, the strong force, and the weak force. Based on their detection in galactic halos and unconventional properties, these fragments prove that Dark Matter exists and is different from what we had previously expected.
Modern physics ushered in new understanding of the types of matter in the universe Through contriving theories, observing galaxy clusters, performing experiments, and collecting data, humans have learned more about Dark Matter. The hypothetical calculations and propositions from the pioneer astrophysicists corroborated with each other. As technology improved, researchers’ data also substantiated the theories by showing the indirect evidence through baryons of Dark Matter, and later on, direct evidence of Dark Matter in the form of WIMPs. Even though we came a long way to learn about this theory, questions still arise. Nevertheless, based on the results from our long term investigation, there is a general consensus that the theory of Dark Matter remains valid.
Askrib, D S, et al. “First Results from the LUX Dark Matter Experiment at the Sanford Underground ￼￼Research Facility.” Physical Review Letters, vol. 112, 4 Mar. 2014.
Bertone, Gianfranco, and Dan Hooper. “A History of Dark Matter.” FERMILAB, vol. 16, no. 157, 16 May 2016. A.
Bertone, Gianfranco, et al. “Particle Dark Matter: Evidence, Candidates and Constraints.” Physics Reports, vol. 405, no. 5-6, 13 August 2004, pp. 279–390., doi:10.1016/j.physrep.2004.08.031.
Clowe, Douglas, et al. “A Direct Empirical Proof of the Existence of Dark Matter.” The Astrophysical Journal, vol. 648, no. 2, 22 June 2006, doi:10.1086/508162.
Moore, Ben, et al. “Dark Matter Substructure within Galactic Halos.” The Astrophysical Journal, vol. 524, no. 1, 10 Oct. 1999, doi:10.1086/312287.
Spergel, David N., and Paul J. Steinhardt. “Observational Evidence for Self-Interacting Cold Dark Matter.” Physical Review Letters, vol. 84, no. 17, 28 Feb. 2000, pp. 3760–3763., doi:10.1103/physrevlett.84.3760.
Turner, M. S. “Dark Matter: Theoretical Perspectives.” Proceedings of the National Academy of Sciences, vol. 90, no. 11, 1 June 1993, pp. 4827–4834., doi:10.1073/pnas.90.11.4827.
Verlinde, Erik. “Emergent Gravity and the Dark Universe.” SciPost Physics, vol. 2, no. 3, 8 Nov. 2016, doi:10.21468/scipostphys.2.3.016.Tags: Okemos High School
Why This Exists by Joseph is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.