[Do the math]

Not one gram of dark mater has ever been found. What are the properties of dark matter? Show it to me. So the acceleration of the universe dose not fit the math, so lets just assume there is dark matter to fix the math to what is observed. What if some of our preconceived notions of the big bang are wrong, and that is why the math is wrong. In particular, we do not know how the density of the universe changed right after the big bang. Based on empirical evidence, the initial expansion was not uniform. This means that we simply do not know how the universe aged at the big bang. Our understanding of the geometry of the universe at the beginning is probably wrong. In which case the cosmological constant may not be a constant, but a variable (not locally invariant). Some interesting research is being done in this area. I have always felt the tensor equations are too rigid in this regard. I think some of the new research in continuous deformation geometry will fit the observed universe better without the need for dark matter.

[Cboldt]

"dark matter" is used to explain the measured rotation of galaxies. If the conventional math is used, the stuff closer to the center of a galaxy would have a shorter "orbit time" around the center of the galaxy, like Mercury has a shorter year compared with earth, pluto, and other planets. But galaxies appear to rotate as if the bulk of stars have the same "orbit" time about the center of the galaxy, regardless of how far they are from the center of the galaxy.