Does Dark Matter Exist Evidence for and Against

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 particles—but 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 term—although 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 today—but 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 rise—such 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 sensitive dark matter detector, have broken some ground in trying to explain dark matter a bit more. In 2020, for example, the Xenon1T collaboration reported what could be a sign of a new understanding of physics, such as the existence of a WIMP (Aprile et al.). However, it could also be due to a previously unaccounted-for background process. Like so much other work on dark matter, nothing is ever conclusive.

What else? The Hubble Space Telescope is still used to try to obtain data on dark matter through observations of gravitational lensing, which helps map the distribution of dark matter in galaxy clusters (Granata et al.). Experiments like the Axion Dark Matter Experiment (ADMX) and are specifically designed to detect axions, which are particles theorized to be even lighter than WIMPs (Chadha-Day et al.). Nothing conclusive has come of this, either—but scientists continue to discuss the topic and research ways to experiment with it.

The “evidence” about axions, WIMPs, and dark matter itself is all entirely speculative and theoretical—as, it must be remembered, gravity itself is but still a theory. Most people would respond to such a reminder with shock, as it has been accepted by much of public as a verifiable fact—but, of course, there are and have been other explanations for the physics of the universe. Dark matter is of interest to scientists because if properly understood it could help to explain some of the bigger mysteries of what is seen by the eye and the telescope—such as what keeps galaxies from breaking up, what keeps them together, and what is really at the heart of the structure of the universe.

For that reason, it is helpful to keep an open mind about the universe and the topic of dark matter, as nothing conclusive has been presented as evidence to date. To date, research is based on theory and speculation, with many articles like the one by Chadha-Day et al. being used to put forward new ideas (for instance in their case the notion of axions being what make up dark matter). But these ideas have yet to be verified and validated. It is much like in any other field where researchers basically try to know what they do not know and cannot firmly verify exists at all in the first place. There is almost a kind of religious or faith-based feel to it in the long run. People try to prove or disprove the existence of God in much the same ways it often seems.

Ultimately, what researchers are doing is trying to understand a mystery by applying the logic and reasoning that they have in a way that makes the most sense. This is a natural scientific method and should not be viewed as a fault. The fault, if ever there is one, is always to be found in the premise or starting point of the argument—the assumption that one has when starting out. For, if the assumptions are wrong, then everything that follows can lead one in a very wrong direction.

Why Dark Matter Matters and What Scientists Hope to Know in the Future

So, that being the case, why does dark matter matter to the average person? Basically, dark matter matters because it has to do with the nature of the universe itself. For example, in earlier eras there were fundamental religious beliefs that what held the universe or the world together was simply the will of God or the gods, as the case might be. Today, rationalism has displaced religion in terms of the scientific field of inquiry. People want hard facts and evidence as to why things are the way they are. They have moved away from religious faith. And yet there are still many questions about how the world works and what keeps the universe’s structure in place. Is it dark matter, for example? If so, how? If not, then what? The question arises in the field of physics, but it could have philosophical ramifications as well.

It is theorized, for instance, that dark matter plays a part in the building of galaxies (Clegg). If this is true, then could people themselves build galaxies by becoming masters of dark matter? Perhaps. Perhaps they could build a world of their own. Or—perhaps that is too much like speculative science fiction. Right now, nobody knows.

The fact is that the theoretical nature of dark matter challenges and tests our current understanding of physics. Because it does not fit anywhere within the Standard Model of particle physics, there is inevitably the suggestion that our current theories are incomplete. From a scientific point of view, an incomplete understanding is like a new frontier where there is work to be done. It is like a place where discovery can still take place. That is why it is of interest to scientists in physics. Discovering the true nature of dark matter could lead to a new understanding of the field of physics. It could even be seen as something that is as groundbreaking as the development of quantum mechanics or the theory of general relativity by Einstein.

Will dark matter studies affect how people live in the future? That depends. If understanding of dark matter is achieved, it could mean all sorts of new things: new technology, new energy, new possibilities in terms of world building and exploration. It could mean new philosophies and new frontiers for travel. But, again, no one knows. Clegg believes that unlocking the secret mysteries of dark matter will help us to understand what dark energy is—and that could help us know more about the universe at its most essential aspect. Still, for the average person alive today, it is quite possible that little ground in practical terms is gained on this topic, considering how speculative the entire field is currently. The CERN particle collider is, for example, like trying to ram two needles together from miles apart at insane speeds (CERN).

That said, new tech has been developed as a result of inquiries into dark matter. For example, the development of highly sensitive detectors for dark matter experiments has led to advancements in particle detection technology. These detectors require ultra-low temperatures and extremely low levels of background noise. The tech developed for these inquires can actually have applications in other areas of science and technology, like medical imaging and national security (Clegg). It also touches on the field of cryogenics, as many dark matter experiments, like those looking for WIMPs or axions, require cooling detectors that go to near absolute zero to reduce noise from thermal radiation. Advances in cryogenic tech may be useful in the fields of materials science and quantum computing (Clegg).

It is all related to the field of science, however, because at root the research is part of the scientific method of inquiry—of asking questions and basing the next moves on evidence. Hypotheses are formed and tested, verified and falsified, and new knowledge is gained. That is how the method is supposed to work—and for dark matter studies it is much the same. The main challenge here, of course, is that a lot of the work remains too theoretical to actually be tested—so there is not much ground covered in short spans of time.

Evaluation

Dark matter research shows that in spite of everything we do know about the universe there is still quite a bit that we do not know—and that is not a bad thing. Just as explorers of old were the ones who helped us know more about the planet we live on, physicists of today are exploring the theories about what keeps the universe stitched together. It is an exciting study in some ways—but it also suggests that other fields of inquiry are equally valid on this subject. Surely there are some things that philosophers and even theologians could bring to the table that could help us inquire as to the nature of the universe and what holds it all together. After all, physicists clearly do not have a monopoly on information here.