Why is dark matter referred to as "dark"?

Dark matter is referred to as "dark" primarily because it emits no detectable radiation. This means that it does not interact with electromagnetic forces in the same way that ordinary matter does, which includes visible light. As a result, dark matter cannot be observed directly; rather, its presence is inferred through its gravitational effects on visible matter, such as galaxies and galaxy clusters.

The phenomenon of dark matter was identified due to discrepancies between the expected gravitational pull from visible matter and the actual motion of galaxies. If dark matter could emit radiation, we would be able to detect it through telescopes, similar to how we observe stars and other celestial objects. However, its invisible nature necessitates reliance on gravitational effects to study and understand its properties, leading to the term "dark."

The other options, while related to light and visibility, do not capture the core reason for the terminology. For instance, while it is true that dark matter is invisible to human eyes, the more compelling reason is its lack of emission of any detectable radiation. The notion that it absorbs light doesn’t apply, as absorption implies interaction, and dark matter, by its very definition, does not engage with light in this way. Finally, while dark matter is indeed prevalent in deep space, it is