dark matter
Definition
A hypothetical form of matter that is thought to account for approximately 85% of the matter in the universe, which does not interact with light or electromagnetic fields, making it completely invisible.
A metaphorical term used to describe elusive or hidden influences, knowledge, or activities that are pervasive but difficult to detect or understand.
Examples
I like to tell myself that my room isn't messy, it is just filled with dark matter that scientists haven't discovered yet.
My motivation to go to the gym on a Monday morning is exactly like dark matter: I am mathematically certain it exists, yet I have never actually observed it.
Trying to find my lost car keys feels significantly more difficult than locating dark matter in the vast, expanding cosmos.