While we have yet to completely describe dark matter, there is clear evidence that it, or something like it, exists. The total mass of the universe cannot be explained simply by what we can see, and nothing we can directly observe fills the gap. While other theories could be constructed to wave away the relatively easily observable gravitational effects, they remain untestable theories, while the gravitational lensing and the rotational rates of galaxies, among other observations, are well documented. If there is no dark matter, the universe has certainly gone out of it's way to make it look as if there were, with evidence! Thus, even if you prefer one of these alternate theories, you must admit that there is at least solid enough evidence to suggest to most astrophysicists, the presence of dark matter.
This is science 101: theories can be tested and proven, and a hypothesis cannot. There are no "theories" for dark matter, and just because there is evidence of something existing or not doesn't absolutely prove anything. It's just a piece of evidence that can be debated. Jan Oort first pointed to some initial observational evidence in 1932. That was followed by further work by Frtiz Zwicky in 1933. That's how the debate started decades ago.
Evidence does exist in the sense that when the mass of the observable universe was tested the observed amount was much higher than the predicted amount. due to the method of predicting the mass of the universe relying heavily on light when the observed amount were found to be higher the extra mass was referred to as "dark matter" as the method of prediction using light could not account for it. therefore as humans coined the term, dark matter most likely does exists we just don't know exactly what it is.
You look into the sky and stars and galaxies are not moving the way you predicted it with your theory of gravity, you do not invent extra matter. The appropriate reaction would be: my theory of gravity must be wrong then. That's falsiciation. Cosmologists are not open for falsification of their theories.
They are basing there assumptions that everything they think they know is correct. If something doesn't fit into their formulas, they just say it is an invisible item that is so plentiful but can't be found anywhere. It may be real but then again it's just as likely that they have incorrect theories as well. After all the Earth was once thought of as flat because everything they knew at the time said it was.
If a calculation won't fit to a observation, the calculation should be reconsidered instead of inventing something to make it fit.
Dark matter & dark energy is the excuse for = We don't know
The bad thing is, it is the same as if we would say: "God did it"
It brings us not one step further, and mankind can lean back (doing nothing to solve it).
I do not believe there is such a think as dark matter. I believe scientists have attempted to throw a blanket over forces they simply do not understand. I do not think we have any proven evidence to support the dark matter theory and I do not see a reason to support it.
Dark matter is an extra-term used to balance the huge misfits between our current theories os cosmology and our observations. For these holes to be filled, we add this parameter. However, for it to explain correctly the trajectories observed of light and mass in the universe, dark matter and dark energy should be 95 % of all the mass and energy of the universe. Additionally, dark matter should be distributed in a completely inhomogeneous, even capricious arrangement, as well as it should have an erratic movement, up to know unpredictable. Furthermore, studies performed with a precise and 100 years extended-in-time observations of the Solar System, our neighbourhood, show no need to account for any extra-mass in order to explain the planets and satellites orbits around the Sun. Suspiciously, dark matter is negligible in the Solar System. These contradictions are a major weakness for a scientific theory, but I think there is a commercial interest in promoting the quest for the dark energy in order to find public investment with "such a cool" concept.
We know matter continually captured by black holes. Who knows how much is in these so-called-holes; and, who can say how to measure something that moves faster than the speed of light (a black hole shows no light therefore matter within must move faster than the speed of light). However, we have no evidence of this so-called dark matter; so why are we trying to make a religion out of it?
Maybe the answer is that the universe is not expanding as supposed; maybe, just maybe it has a rotation to it like the earth-moon system, the solar system, the milky way galaxy, etc.
Stars moving away; or coming towards can also be explained by retrograde motion.
Just because our current math gives us 95% missing matter, doesn't mean our math is correct, or we have enough parameters taken into account. Any argument for its existence is most likely an argument for ignorance, based on what I have researched. Humans are not infallible, math can be incomplete. Until physical evidences comes forth, its as likely to exist as lightsabers.
There is no direct evidence of dark matter, it only makes sense based on our best guesses of the way the universe is constructed. Our understanding of the universe is predicated on certain assumptions, one of which is that to conform to our best models the universe needs about 27% more matter than we can observe. Dark matter is a common answer to that problem in that it would explain where that remaining matter is. However, having an answer that best fills a hole in a problem is not evidence that that answer is correct, only that it fills said hole. Dark matter is a plausible guess, however its actual evidence is scarce, if it exists at all. Filling a hole in a problem, however well, is not evidence.
There are a lot of theories about dark matter. With that being said there are no cold hard facts on this. Some scientist say yes some say no but refuse to use facts. In order for it to be real it has to have some sort of proof behind it. This in fact does not have any evidence.
While there are many theories surrounding whether or not dark matter in fact exists, they are exactly that: theories. There is no hard evidence to prove that dark matter is something that exists in our universe. That being said, perhaps this will change in the future as science improves from its current state.