@johncarlosbaez the possibility that dark matter could only interact gravitationally, being its true nature locked from us, forever, is something I heard on Sean Carroll's podcast some time ago. It caused a great impact on me. Somehow, I want to rebel against that possibility, against that the universe will never allow us to know something so important about it.
@davidsuculum - I sympathize. If you were a mathematician pondering all the dozens of fascinating and vital unsolved problems, not knowing which might be *forever* unsolvable due to Goedelian incompleteness, you might feel even worse. But I doubt the universe feels any obligation to share its secrets. So we should probably just relax and enjoy the mysteries, even as we try to figure things out.
The good news is that we are getting so much purely gravitational information about dark matter - through gravitational lensing, and its effects on galaxies and galaxy formation - that it's becoming extremely tricky to fit all the data we have with a model that's not quite elaborate.
@davidsuculum - I sympathize. If you were a mathematician pondering all the dozens of fascinating and vital unsolved problems, not knowing which might be *forever* unsolvable due to Goedelian incompleteness, you might feel even worse. But I doubt the universe feels any obligation to share its secrets. So we should probably just relax and enjoy the mysteries, even as we try to figure things out.