If it weren't sad it would be funny. I've been advised by a highly respected nuclear physicist that Dark Energy is an entirely unproved theory. What gives? Our classical and quantum scientists are closing their eyes to the evidence of dark energy that has been measured to proliferate our universe. It seems that the thinking related to an expanding universe can be 'condoned' but all that hard work applied by our astrophysicists that relates to 'dark energy'? That, apparently, can be entirely ignored? Not sure why. Possibly because it's not yet found a foothold in conventional thinking
Frankly I'm entirely unconvinced that the universe is expanding at all. Indeed I'd only be surprised if there was NO evidence of a variable shift - that red shift thing. But I'm possibly not the best authority to argue this. lol. In any event, what I do know is this. If galaxies collide - yet the universe is expanding - then that rate of expansion must be both VARIABLE and LOCALISED. Not the best premise for any arguments at all. Bear in mind our own authority of all things quantum is from John Stewart Bell who states that the 'statistical predictions of the quantum theories.....cannot be upheld by local hidden variables'. Here's how I see it. Galaxies are moving through space at variable velocities. Which means that their velocity must exceed the rate of spatial expansion else they would NEVER connect with each other. If some move at the required velocity and others do not - then we're introducing precisely those variables that are discounted by Bell. The universe would then be entirely chaotic. And that will put paid to our quantum theories. Quite apart from which - where we may see galaxies colliding - we're looking back into history that very often precedes the birth of our own galaxy. What definitive proof is there that those galaxies are even still 'extant'? I don't think anyone has found an argument for absolute proof of this. It's all theoretical. So far - in any event.
What is NOT arguable - however, is the fact that those galaxies are exceeding the gravitational pull required by our Newtonian physicists. For some reason this is 'swept under the carpet' and there are no attempts - ANYWHERE - to resolve this.
Except my own. LOL