This is a very delicate subject to astrophysicists. Why? Because it forces them to believe in something that just can not be proven and probably never will.
Let me explain Dark Matter is nothing but has density, weight and gravity.
I know the brain goes Whoa! Then it is something, right ? No because there is no substance.
Let me illustrate the problem with a metaphor of an elephant for the universe.
Picture an elephant (Loxodonta Africana) that normally weighs about 12 tons. But when you weigh that elephant, that acts and behaves like an elephant, you find he weighs only 1,104 pounds, about half a ton. The elephant should not be able to move or act or have the strength to do what he does unless he weighed 12 tons. But every time you weigh him he is about half a ton. Where is the other 11.5 tons? That is the problem!
In our universe we watch the most amazing things and weigh the observations but what should be there and what is there doesn’t make sense.
Here is the break down: Results from the WMAP team in 2008, which combined data from the CMB and other sources, indicate that the universe today is 72% dark energy, 23% dark matter, 4.6% regular matter and less than 1% neutrinos.
Wow 23 % dark matter and 72% dark energy that’s a lot of nothing!
Now you understand that nothing has to be there or the universe can’t be doing what its’ doing.
Now I understand why computers just will not work no matter what you do to them.
It’s Dark Matter in the computer! 🙂