I have two questions. They are related, but different enough that I think it makes sense to raise them in two separate threads. The first concerns 'dark matter'. The NYT article is a good example of what is bothering me: https://www.physicsforums.com/showthread.php?t=160464 (Please excuse the long-winded nature of my question. I am having difficulty formulating it concisely.) As I understand gravity (which is only in simple terms), it is an observed phenomenon with no underlying rationale. Newton and Einstein have described it mathematically and experiments agree with their descriptions extremely well. They did, that is, until careful examination of the behavior of large assemblages of objects, such as galaxies, revealed a substantial discrepancy with their predictions. As a naive cosmologist, but en experienced scientist, my first instinct would be to suspect that the math simply doesn't account for some behavior that is associated with extended groupings of massive bodies, including large numbers of stellar objects and unknown numbers of black holes or other super massive objects not yet identified. Why postulate the existence of a form of matter that interacts with the matter we can detect only by gravitational influence? I am aware that there have been attempts to reformulate the mathematics of gravity to explain the discrepancy, but the few I have looked at (and can understand a bit) do not seem to be fully baked. Has the 'scientific community' concluded that the current lack of success in describing the observations by altering the mathematical formulations implies that no such description is likely or even possible? The postulate of dark matter seems even less appealing to me, sort of like the classic Sidney Harris cartoon showing an intricate formalism interrupted by, "Then a miracle occurs", from which it continues on to the conclusion. I must be missing something important. What is it about non-baryonic particles that is so compelling that it causes very intelligent analytical thinkers to make enormous extrapolations about the nature of matter in the universe - with hardly a sign of the tentativeness I would expect of such a departure from direct experience? Is it the result of their familiarity with the question? Or is it just the nature of the popular press to take the idea and run with it, neglecting the rigorous inclusion of caveats? Included in my thoughts are cases where mathematical conjectures that seem intuitively obvious, or at least plausible, exist for decades, even centuries before someone finds a way to prove them. Why be dismayed that a mathematical reformulation of the relationship between mass and gravity that accurately describes what we are observing in non-local environments hasn't been found yet? On the other hand, and here's where my question really gets convoluted, if the 'beauty' of the current gravitational theory is just too magnificent to alter, then what's so dumfounding about the properties of these new postulated particles? What, exactly, do we know about conventional gravitational attraction between 'normal' matter that we do not know about these new hypothetical particles? Isn't it all a mathematical construct to quantitatively describe what we observe? There is no first principle that requires the mutual attraction of objects based on mass. We just observe that it occurs and do our best to describe it in a way that is useful. Right? Or am I missing something again?