What is Dark Matter? Observations on Galaxy Glue

Introduction

Dark matter is something that very little is actually known about; it is a topic that many have speculated about but none have explained completely. The term dark matter was first used by Fritz Zwicky in the 1930s to describe the matter that makes up most of what is believed to be the mass of the universe (Hossenfelde and McGaugh). In other words, Zwicky looked to the skies and tried to make sense of the seemingly all-prevalent matter that does not emit or absorb or reflect light at all. In fact, the only way anyone knows dark matter exists at all is through its effects: gravitational pull, radiation, and the overall structure of the universe itself, which suggests that dark matter must be present. With that said, however, the best that anyone has been able to do to date is hypothesize about what this glue that seems to hold the universe together actually is, why it is dark, and what secrets it contains. This paper will review this subject and what the research on it has shown till now as well as what scientists are hoping to find out about dark matter in the next few years.

Background

The basic concept of dark matter is this: for starters, it cannot be viewed by a telescope. It is invisible to the human eye because it does not interact with light at all (Rubin). Actually, the only reason Zwicky was able to assert it existed at all was because he made an inference based on what he believed to be gravitational effects: he surmised that galaxies far away rotated at such slow speeds that one could wager that more mass was present in them than the eye could see. Zwicky suspected that if this extra mass was not present, galaxies would fly apart due to their rotational speed. Thus, dark matter really was in his hypothesis a type of galaxy glue.

Dark matter has to be defined in such generic terms as galaxy glue because no one really knows exactly what it is (if it even really exists). It has none of the make-up as other things that people can see and observe: it shares no particles with stars or planets (Clegg). Scientists have a Standard Model of the physics of particlesbut dark matter simply does not fit into that model. Some researchers, therefore, think dark matter could consist of new particles that simply have not been discovered or understood just yet. For that reason, scientists are still researching the field and trying to understand more about it (Clegg).

Since dark matter itself is undetectable by the naked eye and somewhat indescribable outside of speculative theory, it is helpful to know at least some of the terms used whenever the topic of dark matter is discussed.

First, there is galaxy. A galaxy is a collection of stars, gas, dust, and dark matter, bound together by gravity (Clegg). Gravity is another important termalthough not scientifically defined as a force, it is often described in terms of having force on other objects: it is theoretically defined as the thing that attracts two bodies with mass and that keeps planets in orbit around stars and that governs the large-scale structure of the universe (Rubin). Gravity is often taken for granted as something that exists todaybut it is actually still just a theory and not a law. There are in fact other explanations for why things fall, why things float, and why things risesuch as the ether (Boersma).

Another helpful term, although also theoretical and speculative, is Weakly Interacting Massive Particles (WIMPs). WIMPs are hypothetical types of dark matter particles. It is speculated by some that WIMPs explain what dark matter is (Clegg). Gravitational lensing is another term that is often used in conjunction with dark matter research. It refers to the bending of light from a distant source, like a galaxy, by the gravitational field of an object, like another galaxy (Granata et al.). This effect is used to map dark matter, and the Hubble telescope is used in this kind of work.

All in all, the vocabulary needed to thoroughly discuss dark matter is actually quite extensive, but these terms are helpful enough to get started.

Recent Work

The most interesting recent work on dark matter is done at the Large Hadron Collider (LHC), which is the world's largest and most powerful particle collider located at CERN. It is used in experiments that could provide insights into dark matter (CERN). CERN notes that the Standard Model is a collection of theories that embodies all of our current understanding of fundamental particles and forces[however], although the Standard Model is a very powerful theory, some of the phenomena recently observed such as dark matter and the absence of antimatter in the universe remain unexplained and cannot be accounted for in the model (CERN 6). Thus, the work that CERN is doing in trying to smash particles together to better understand energy is also important in seeing if an understanding of dark matter particles can be obtained.

Lisa Randall writing for Nature states that is an elusive substance that permeates the universe exerts many detectable gravitational influences yet eludes direct detection. However, Randall explains that dark matter should really be called transparent matter since light simply passes through it. Like many other scientists, Randall is hoping that the Large Hadron Collider at CERN near Geneva might in the future detect dark matter particles through its own experiments with particles.

Recent work like the Xenon1T experiment, which is the world's most...…much of the universeaka dark matter. It is a peculiar matter, and yet our understanding of it is theoretical and based largely on acceptance of another theory (gravity). But what happens if one rejects the theory of gravity and asserts rather the theory of ether instead? Does the matter of dark matter suddenly lose all relevance? These questions are worth asking if one is going to develop a model of the universe.

The take home message of all this information is simply this: inquiries like this one can actually open the door to new discoveries in surprising directions. Tech developed for research in one field can end up benefitting other fields, like medicine or security. This suggests that inquiry is a good thing, because you never know where it will lead or who it might help or how. Dark matter itself is likely to remain a mystery for some time, but that does not mean it should not be pursued as a course of inquiry. The fact that CERN exists and that methods of attempting t detect dark matter are being implemented shows that there is enough investment and interest out there to try to figure out what it all means, what impact it could have for energy, and how it could benefit the lives of people on this planet. So, the take home message is this: ask questions, apply appropriate theory, and critically think about what could help answer the questions.

Conclusion

In conclusion, dark matterfor nowis best understood as the glue that holds the galaxy together. What it actually isor how to define itis really still up in the air. Scientists are trying to figure it out with various models, experiments, detection methods, or by trying to smash particles together at CERN. New tech has been developed out of all this that could benefit different industries and fields. But are we any closer to unraveling the mysteries of the universe? Maybe this is why in the Middle Ages people were willing to accept that the glue that held the galaxy together was God and just left it at that.

Works Cited

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Clegg, Brian.Dark matter and dark energy: the hidden 95% of the universe. Icon Books, 2019.

Granata, Giovanni, et al. "Improved strong lensing modelling of galaxy clusters using the

Fundamental Plane: Detailed mapping of the baryonic and dark matter mass distribution of Abell S1063."Astronomy & Astrophysics659 (2022): A24.

Hossenfelder, Sabine, and Stacy S. McGaugh. "IS DARK MATTER."Scientific American319.2

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Randall, Lisa. What is Dark Matter? Nature (2018).

https://www.nature.com/articles/d41586-018-05096-y

Rubin, Vera. "Dark matter in the universe."Scientific American1 (1998): 106-110.