Is it rational to believe in the existence of viruses but not to believe in the existence of dark matter?
Viruses, not lions, tigers or bears, sit masterfully above us on the food chain of life, occupying a role as alpha predators. —Claus Wilke and Sara Sawyer, virologists at the University of Texas at Austin and the University of Colorado Boulder
I think it’s ethically dubious to run the Olympics when you’ve got an epidemic of a virus that we don’t understand very well.—New York University Bioethicist Arthur Caplan
You know, dark matter matters. — Neil deGrasse Tyson
We called it dark matter, but dark refers to our ignorance, not to the colour of the stuff – Saul Perlmutter, Nobel Physicist
There is a long tradition of scientists attempting to analyse questions that are primarily philosophical in nature. Here, we are being asked to reverse the approach: to answer a philosophical question regarding our confidence level on the boundaries of our scientific frontiers. Many scientists would question this approach, and perhaps the validity of the question itself.
But, it is both a valid question and an important endeavour to refine our thinking on the philosophy of science. The importance of the philosophy of science is that it sets a standard for identifying what constitutes scientific knowledge. Perhaps we can understand what is rational by examining and answering this question as fully as possible, to determine what qualifies as genuine knowledge versus intuition. In the question that is posed, we are compelled to examine the limits of our abilities in biology and physics and determine what qualifies as actual knowledge versus speculation at the ‘event horizon’ of our current compendium of scientific understanding. In 2020, for biology, it is the comprehension of the mutation of viruses that sits at the frontier of our knowledge. In physics, many scientists would argue that the boundary of our current knowledge is the study of dark matter.
Science, historically referred to as natural philosophy1 makes use of reasoning, questioning, and analysis whereas philosophical analysis is the study of rationality. This can be summarized as: scientific knowledge = knowledge of causation. It is with an understanding of causation that we should apply our evaluation of these two phenomena and thereby gauge the level of rationality that we are able to defend in philosophical framework.
From a very simplified perspective, in biology we generally build on existing observable information and then extrapolate to bigger concepts. In physics we tend to begin with expansive concepts and then seek evidence to support or refute the underlying theories. So, philosophically speaking, these two vital scientific arenas may have very different origins, and potentially contrasting trajectories, but they both ultimately require evidence (and repeatability) to ensure that each of the ideas or theories contemplated conform to the ‘scientific method’ of analysis. Biology uses an empirical or heuristic approach, or in other words, biological discoveries are often found through inductive or ‘a posteriori’ proofs. In physics, we tend to use an ‘a priori’ approach, wherein we begin with reasoning that is borne out of theoretical deduction rather than from observation or experience; we use the observation to reaffirm the theoretical predictions made before gathering evidence.
In applying a scientific method to the philosophical question of: “Is it rational to believe in the existence of viruses but not to believe in the existence of dark matter?”, we focus on comparing and contrasting how we might use a) observation, b) interaction, c) measurement, and d) the ability to predict the behaviour of viruses and dark matter to determine their legitimacy.
Observation
The first fundamental approach to deepening our understanding of biological mechanisms is to observe them; in the cases of viruses, it is on a microscopic level. Our microscopes are now so powerful that we can see extremely small things, even single viruses. With the improvement of microscope technology, we have gained the ability to observe the internal processes of a virus, such as reproduction, and explain its 7 stages in great detail: attachment, penetration, uncoating, transcription, synthesis of components, virion assembly, and virion release (liberation stage).2 So, not only are we able to see viruses, but we are able to observe some of their most intimate processes.
The first observations of dark matter were made possible by the use of powerful new telescopes by a Swiss observational astronomer in California. In the 1930s, Fritz Zwicky, who worked primarily at two historically prominent observatories, Mount Wilson and Palomar, was studying Hubble’s observations of galaxies. To quantify his observations, Swicky borrowed a theorem from thermodynamics and applied it to an anomaly in the motion of this Coma Galaxy Cluster. He applied the virial theorem to the Cluster in order to estimate its mass by calculating the average kinetic energy and velocity dispersion. He found that 800 galaxies of 109 solar masses in a sphere of 106 light-years should exhibit a velocity dispersion of 80 km/s.3 In contrast, the observed average velocity dispersion along the line-of-sight was approximately 1000 km/s. From this comparison, it became possible to surmise that dark matter is perhaps more abundant in our universe than luminous matter. So, at the galactic level, it started to become clear that dark matter does exist, or at least that there were forces that could be observed that could counter this kinetic energy.
Interaction
The second causal relationship that we can acknowledge is that we interact with viruses. Or, more accurately, viruses interact with us. And, most of the time, they interact with us in ways we usually do not greatly appreciate: viruses can make us ill. Some, if not most, of us have suffered from influenza, one of the most common forms of viruses. Viruses can proliferate from individual occurrences, to community level ailments, to epidemics, to pandemics. Fortunately, in many instances, our immunological defence systems can deploy an army of white blood cells to destroy most viral invaders. And, in many cases, modern science enables us to interact in a manner that gives us control over viruses through vaccines.
However, when it comes to dark matter, it interacts with us on a cosmic scale, which is certainly much more expansive and impersonal. Vera Rubin gathered evidence to reveal that a vast amount of unseen matter is interacting to hold galaxies together.5 This is also seemingly true in the Milky Way, the galaxy that we call home. But, does dark matter interact with each of us? Dr. Dan Bauer, who leads the Cryogenic Dark Matter Search (CDMS) project, believes that dark matter is all around us and moves as particles throughout the universe, including our bodies. He uses advanced germanium detectors which are in a lab at the bottom of an abandoned iron mine, half a mile below the earth’s surface, to try and detect and interact with dark matter. He uses the core of the earth, and other filtering materials, to isolate and detect dark matter which only ‘weakly interacts’ with the visible matter all around us. Dark matter is considered to have mass (of less than 10 times the mass of the proton6) but interacts so weakly with visible matter that they are referred to as weakly interacting massive particles (WIMPs). But, the detection of WIMPs has thus far been less than gratifying. Indeed, it could transpire that WIMPs totally evade detection by our current methods of measuring interaction. According to Andrew Pontzen, of University College London, “You can imagine a scenario where dark matter particles turn out to be so incredibly weak at interacting with normal matter that our detectors will never see anything.” If this is the case “You would then be saying we can only make sense of the universe by proposing a hypothetical particle that we can never detect,” says cosmologist Andrew Pontzen, of University College London. “Philosophically that is a highly unsatisfactory situation. You would be saying you cannot prove or disprove a key hypothesis that underpins scientific understanding.”8 On the basis of interaction, we have a high degree of confidence we can believe viruses exist, but less reassurance regarding dark matter.
The third factor relates to the measurements we can apply to viruses and dark matter. When people fall ill from viruses, it is because they have been exposed to a ‘viral load’ that overwhelms their unsuspecting white blood cells. A method for determining this ‘viral load’ is plaque assays which measure quantity by determining the number of plaque forming units (particles per mL) within a type of assay. A higher viral burden correlates to the severity of an infection and can be measured by estimation, by example, by the number of RNA copies per millilitre of blood plasma.
Further, we have also identified the determining factors in their size and shape: the amount and arrangement of proteins and nucleic acids within the virus. With all of this, we can conclude that we can track, measure and ascertain the levels that will adversely affect an individual with a reasonable level of predictability.
With regard to dark matter, we examine our ability to measure it at a cosmic scale. In the 1970s, Vera Rubin built upon the early work of Zwicky, by training her telescope on the Milky Way’s closest galactic neighbour, Andromeda. Like most galaxies, it had a dense central concentration of stars. She focused on understanding galactic rotation curves; she expected the billions of stars circling around the central bulge to orbit just like the planets in our solar system. She anticipated that they would obey Newton’s laws of motion in that, the further away they are from the centre, the slower they would orbit. It took Ruben two years to obtain the empirical evidence that measured the velocity of 90 stars in the Andromeda Galaxy. The results were very different from what Newton would have predicted. All of the stars were moving at a uniform velocity of 250 kilometres per second, regardless of how far away they were from the visible mass at the centre of the galaxy. The only explanation, and one consistent with Zwicky’s early predictions, was that there exists a large amount of matter holding these objects in the observed rotation curves. But, as before, it was not observable in the spectrum of visible light or radiation.
Predictability
We know when both viruses and dark matter are present, based on our ability to observe and measure them, but there are a number ways in which they are unpredictable. Viruses are relatively ‘known’ entities until they mutate. Mutations can be spontaneous and, as a result, it takes time (long cycle time) for us to understand the manner in which a mutated version might function or be cured.
In the case of dark matter, we have developed the ability, based on the work of Saul Perlmutter and his Nobel Prize winning team, and the work of Richard Massey of Edinburgh University, to predict its location and scale based on calculations related to interactions with light. Massey focused on using gravitational lensing to show how the dark matter bends light. He observed that galaxies, in a line of sight, appeared distorted as light passes by dark matter causing a visible gravitational lens arc. According to Pat Scott of Imperial College London, “The fact that the lensing happens at all means that there is some additional mass there, which has to be dark matter.” Further, because dark matter can bend light rays, it is likely having a similar effect to Einstein’s proposed theory that massive objects have an effect on light rays and the fabric of space-time. But, this is the extent of our predictability of the effects of dark matter and to interact with it in any meaningful way, which has given rise to both scepticism and the exploration have alternative theories.
There are several alternative theories, including variances of string theory, Modified Newtonian Dynamics, and a hypothesis by Erik Verlinde who claimed to have “evidence that this new view of gravity actually agrees with the observations” and properties that were originally assigned to dark matter. He argued that Einstein’s principles of gravity were not applicable on a large scale and that parallel modified theories of gravity such as MOND11 were more plausible.
While there are alternative theories for virus mutation, there are no reputable arguments for questioning the existence of viruses. By contrast, there continues to be fundamental questions regarding dark matter.
Conclusion
Our understanding of dark matter is 100 years transposed from the point in time in which we discovered and developed our understanding of viruses. However, we must admit that our understanding of dark matter is limited and perhaps the comparison between viruses and dark matter is both unfair and premature because we have only known about and embarked upon studying dark matter relatively recently.
There does exist significant measurable information, not speculation, that there is an unobservable phenomena that has played an integral role in the formation of our universe. Nevertheless, the fact that we have assigned the name ‘dark’ to it does highlight our admission of our ignorance of the details of it.
Perhaps, it is reasonable to draw an analogy to our understanding of gravity. We are still somewhat unaware of the causes of gravity, whether the particles we call gravitons actually exist and whether they are the mechanism for exerting gravitational force. We have never captured a graviton. Is it then rational to say that gravity doesn’t exist? I don’t believe any rational person would make such an argument. The truth is, we have had several centuries to understand gravity fully, but to date we have failed to do so, and yet it’s necessary existence is a firmly held belief.
On this basis, it is reasonable to state that there is enough evidence for the existence of dark matter, even though we cannot yet attribute specific qualities to it. Some have argued that it is too hard to study dark matter but Chamkaur Ghag disagrees: “I think it is ridiculous to suggest we stop,” he said. “Are we just going to say ‘OK, we have no idea what makes up 85% of the universe just because we are finding it all a bit hard’?”
It is important to continue to undertake the difficult effort involved in studying elusive phenomena. If we had denied the existence of viruses or dampened our intensive efforts to understand them better, we would be in a far worse place in history than we find ourselves today.
So, it is irrational to deny the existence of dark matter, regardless of whether debates on its traits, characteristics, how we might interact with it, and predictions of its behaviour might continue. Just as we believe in the existence of viruses and the importance of our understanding them, believing in and understanding dark matter will matter.
1 ‘Prior to the nineteenth century, those who are now regarded as scientists were referred to as natural philosophers.’ Arran Gare (scientist and philosopher)
3 Gianfranco Bertone and Dan Hooper, A History of Dark Matter, FERMILAB-PUB-16-157-A.
5 http://www.ifsc.usp.br/~hoyos/courses/2017/FCM0101/Vera-Rubin-Dark-Matter.pdf
6 https://www.space.com/20930-dark-matter.html
11 Modified Newtonian Dynamics, Mordehai Milgrom 1983.
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