Earlier today I read several articles relating to the discovery of a galaxy that was found to be nearly entirely missing dark matter. While it is easy to ponder how it is that something like dark matter that is already entirely invisible can go missing, the fact that it can be recognized that this new galaxy is missing dark matter is actually a good thing, even if it is an odd thing, and as might be expected, this has some implications that go well beyond astronomy  in terms of interest and relevance. Let us note, though, that simply because something is invisible does not mean that it does not exist or that its existence cannot be inferred by other means. Indeed, the example of dark matter being missing in a galaxy has some implications about how the existence of the invisible may nonetheless be understood. After all, that which is visible was made by that which is invisible, so this has a pretty serious level of importance in understanding.
To put this discovery in context, let us look back a bit more than a century ago. During the late 1800’s, it was commonly believed that the earth moved through a substance known as the Æther, which is how light was able to move as a wave through space. The Michelson-Morley experiments in 1887 indicated that this substance did not exist, which was further confirmed in later experiments decades later, and an invisible substance that had been posited to solve a particular problem with regards to astronomy was laid to rest except as a poetic term that is still used on occasion even today. Just as the luminous Æther had been posited as a way to explain the propagation of light, so too dark matter had been posited to explain the formation of galaxies and the disconnect between the visible mass of the universe and the relatively high density that we find in galaxies like our own.
Yet the fact that we can differentiate between the majority of galaxies that we see with large amounts of dark matter and a somewhat odd galaxy that apparently has little or no dark matter suggests that dark matter actually exists. After all, we would not be able to recognize a difference between presence and absence unless there was something actually there to measure. Its existence may be shadowy and difficult to determine, and it may of course be impossible to see directly, but the evidence of its absence in a particular case is simultaneously an evidence of its presence in other cases. The fact that one can distinguish its presence from its absence suggests, in other words, that there is something to see. We might note the same thing in other circumstances where the existence of the invisible is to be inferred by its interaction with the visible, and where the ability to distinguish between cases where that interaction is present and absent itself becomes evidence of the presence of the invisible can therefore be inferred with a high degree of confidence.
This does not mean, of course, that this discovery is without practical applications. I can think of at least two areas where this particular discovery may be seen as having some immediate implications that people can draw. On the one hand, those who have claimed that dark matter is necessary (especially in large quantities) for the formation of galaxies in the first place will have to amend their views. It is possible that certain shapes and sizes of galaxies require the presence of dark matter to force a high degree of cohesion necessary for those shapes, but clearly now we have at least some evidence that galaxies can form without dark matter. Perhaps now that we know such galaxies exist they will become more common. This was the case, after all, when Pluto, previously an eccentric planet viewed as the only one of its kind become merely the first of a relatively common kind of minor planets called plutonoids named after their first discovered example. The same sort of phenomenon is quite possible here, since the fact that we know that there is something to look for regarding fairly dim galaxies with little or no dark matter means that we can see how common they are, since what happens once is likely to have happened more than once in a universe as large and as old as our own.
For those of us who are spiritually inclined, the implications are obvious as well. When we look at the involvement of God in history, we can compare and distinguish cases where divine providence is present from those cases where it is absent. The recognition of a difference between, say, the destruction of the Assyrian army miraculously during the time of Hezekiah and the absence of divine involvement in the bloody and largely indecisive battle of Qarqar some 150 years previous to it is the same sort of situation. When we can see the influence of the invisible on the visible, as well as the occasional absence of that influence, we can feel confident that we are dealing with something genuinely in existence and not merely a fictitious if poetic nonentity like the Æther. And it is for this sort of reason that discoveries of the absence of something are just as important as discoveries of presence, for it is by recognizing occasional absence that we can feel comfortable with a belief in presence in the first place, as paradoxical as that may seem.
 See, for example: