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Other cosmologists suggest we can only see about 10% of our universe through such devices as telescopes, orbiting cameras and sound equipment. In the 90% that remains is the real mystery, the area known as 'Dark Matter.' Inside this 'Dark Matter' exists black holes. It is difficult to prove the existance of black holes because they are defined as what they are not. They consist of no matter, no space and no dimension. They only way they can be detected is using X-rays to detect the pulsars of radiation.
The only trace we have of black holes, is what black holes leave behind. A good example of this is the disappearance of any stellar neighbours such as stars.
Black holes suck up everything that comes near it, as if the hole was quicksand or a drain in the sky emptying into an unknown. If you were to go into a black hole, there would be no way to come back to report what you found there, not to mention you would be crushed like spaghetti.
As in this photo, if a star were to come close by, at first the dust and gases from that star would be siffoned in, then any of the star's satellites (like planets and moons) then finally with one fell swoop, nothing remains but complete darkness.
Black holes are difficult to spot, scientist can only infer the properties of them. Holes are very dense, meaning heavy-duty gravity and they emit radiation jets from either of its poles, like an exhaust system. This product is called a quasar. Some quasars produce more energy than hundreds of galaxies put together.
There is a MMT (multi-mirrored telescope) at Smithsonian University of Arizona that specializes in spotting quarsars.
So what is behind these 'doors' that lead out of our universe? What is at the edge of all time, space and dimension as we know it? We don't know what lays behind these black holes. It unlikely that we will know anytime soon because anything that explores their inside never come back.