Dark matter may not have been detected yet, but we don't need to detect things directly to prove their existence. Sometimes, enough circumstantial evidence is s

Dark matter may not have been detected yet, but we don't need to detect things directly to prove their existence. Sometimes, enough circumstantial evidence is sufficient. For example, if you see a human-shaped shadow around the corner, you can safely assume that it's probably a human, even if you can't see them directly. It may of course turn out to be something else (maybe a scarecrow!) but that's okay. Black holes are similar: we can't observe them directly but we can detect their gravitational effects, such as the way they bend light around them.