It isn’t actually matter. We’ve all heard it called that so many times, though, we subconsciously anchor our thinking around what we know about matter. That’s called cognitive bias.
The reality is, dark matter is better referred to as dark gravity. We can observe its gravitational effects on planetary orbits. We can measure it just like we measure gravity on Earth. And we know it makes up as much as 95% of the Universe. But we don’t yet know what, exactly, causes it. One thing we do know–it’s not matter.
Just goes to show, the most brilliant minds in human history suffer from cognitive biases from time to time. The only way to mitigate the effects of our own, subconscious dark gravity is to be mindful that cognitive bias affects the best of us.