I just wanted to start a discussion about the lecture on dark matter presented by Dr. Polhemus and see what others thought about it. I thought the presentation was phenomenal and was very impressed by the ideas and information, but afterwards I was troubled by some questions and doubts.
I guess my overall question revolves around when and how a concept like dark matter can become knowledge. Currently, we are not able to perceive dark matter with our senses. Some scientists have made theories about it because it seems to explain some occurrences in space, but do they know that dark matter exists? What do they need as evidence to claim that it does exist? Do they need more examples like the bullet cluster? If so, how many more? Also, when will the average person be able to claim it as knowledge? Most people can not understand these theories because they are so complex. Are the scientists a reliable authority for the general population?
Here's a link to an article on some of the general ideas and the bullet cluster if you missed the lecture or if you're just looking for an interesting read: