Theory: perhaps dark energy is only gravity. That's why we can't detect it, only see its effects. Maybe our universe is just an irregular bubble in a very large black hole. That would account for gravity being all round the perimeter of our universe pulling the galaxy's to the edges. Then what? Why did the bubble form? Heat is a basic catalyst to create a reaction. Is the center or creation point of our universe becoming a larger void or is it full of fairly uniform matter like the rest of the universe? Food for thought. Good day. Chrisb
PS; A very small spec of a black hole would contain a huge amount of matter, perhaps a universe full.
