There are various concepts to try and describe what it might be; such as black holes
or "string theory".
If you look up black holes on Wikipedia you will find the following statement
observations have resulted in the general scientific consensus that, barring a
breakdown in our understanding of nature, black holes do exist in our universe." This
roughly translates as "there are some observations that fit with the theory of black
holes and with some of the rules of the Universe, so black holes must exist". Slightly
flimsy proof, if proof at all.
Richard Dawkins is quoted as saying that
"we now know 90% of everything". This is
ironic, when the reality is that we
don't know about 90% of everything.
From what we currently know, spiral galaxies should break up, with stars flying off in
all directions. Some people have said that it is almost like there is an invisible hand
holding the galaxies in place.
Colossians 1:16, 17 "For by him all things were created: things in heaven and on
earth, visible and invisible, whether thrones or powers or rulers or authorities; all
things were created by him and for him. He is before all things, and in him all things