What characteristic makes dark matter difficult to detect?

The characteristic that makes dark matter difficult to detect is that it does not emit or interact with electromagnetic radiation. This means that dark matter does not produce light or any form of electromagnetic radiation that we can observe with telescopes. Traditional detection methods in astronomy rely on detecting light from objects in the universe, but dark matter does not interact with light in the same way that normal matter does. This is why it remains invisible and undetectable through conventional optical telescopes.

In contrast, while other aspects of the universe can influence the detection of matter, the lack of electromagnetic interaction is a defining feature of dark matter. Its presence is inferred through its gravitational effects on visible matter, such as the rotational speeds of galaxies and the motion of galaxy clusters, rather than through direct observation or emission of light. This indirect approach underscores the elusive nature of dark matter and highlights the challenges scientists face in confirming its existence and understanding its properties.