Dark Matter is required to exist because without it all galaxies would fly apart. In our Milky Way Galaxy Dark Matter accounts for 90% of the entire mass of the galaxy. Dark Matter is simply that, Dark. As it cannot be seen and has a very weak force. It only interacts with gravity.
Yes this is true. We have recently discovered dark matter exists with the help of the Hadron particle collider, but can not see dark matter. (not yet any way)
'Dark matter' and 'dark energy' have not been observed or proven yet.
What exists at the center of a black hole. Why is dark matter unaffected by photons. What is dark energy. Examples...
We know that dark matter exists because it got gravity, though it is invisible. It hold galaxy and Universe. There is a theory there many other parallel universe outside our universe and dark matter holds those universe up and some scientists says that dark matter are just mass of the matter of the parallel universe. It sounds crazy but that is the Law of Physics. However there is not exact explanation of what dark matter really is, so there are still Noble Prices for those who can come up with a reasonable explanation
There is a lack of OBSERVED matter, but it is quite clear (due to gravitational effects), that dark matter indeed exists. There are all kinds of pieces of evidence in favor of dark matter. It isn't known yet what it is made of.
Most matter in the universe exists in the form of dark matter and dark energy, which are currently not fully understood by scientists. These two components make up the majority of the universe's mass-energy content, with ordinary matter (protons, neutrons, electrons) making up only a small percentage.
We're not certain that "dark matter" even exists, or what the proportions of "normal" to "dark" matter is. I have read some articles saying that the ratio might be as much as 20-1; 20 parts dark matter to one part normal matter, but these are predicated (I believe) solely on rough calculations based on the perceived mass of the galaxy and its apparent rotational speed.There appears to be a great deal of speculation and estimation in these calculations.One important trait of a scientist is to NOT GUESS about things that we don't know, and to admit the boundary between the known, the believed, and the unknown. Even if the current hypotheses about dark matter and dark energy turn out to have some basis in reality, we will certainly be surprised by the truth when we finally learn it.
Dark matter is a mysterious substance that does not interact with regular matter, so it is unlikely you would be able to walk through a wall made of dark matter. Our current understanding of dark matter is that it exists in a halo around galaxies and does not clump together like regular matter to form solid structures like walls.
Dust, gas, dark matter, perhaps individual stars and planets.
We do not know as we have not found any dark matter to examine. The only way we detect it and know it exists is due to its gravitational attraction of the ordinary matter we can see. One speculation when neutrinos were discovered to have tiny nonzero masses was that dark matter might be neutrinos. Another speculation is that dark matter is only ordinary matter, but its in another separate universe in a shared higher dimensional spacetime. Nobody knows.
Neither, dark matter is an undetectable yet massive existence within our universe. It is spread out relatively smoothly, not bunching up in particular locations. For more information, search dark matter images (computer simulated), they help the visualization of it.
There is no opposite of dark energy in the sense that there exists something that is the exact opposite of dark energy. Dark energy speeds the rate of expansion of space, even empty space, and gravity, mass, or matter causes the opposite in that it causes a decrease in the rate of expansion of space in areas that have matter.