The universe is expanding at an accelerating rate. Everything is moving away from everything else, and the rate at which everything is moving away is increasing.
One hypothesis to explain this is to posit the existence of dark energy. We say that empty space actually has a mass, a negative mass, and say that when you get enough of nothing all in one place, it applies a negative gravitational force which pushes away surrounding matter. This then explains the accelerated expansion of the universe, for, it is the empty space that is pushing everything apart.
Another hypothesis is Modified Newtonian Dynamics, which just makes some small adjustments to Newton’s laws in order to say that on a very large scale, it is the nature of matter to accelerate, and this effect is just diminished with smaller matter.
I’ve been doing some lay contemplations on the matter, and had another idea.
Let us assume that the universe is infinite, having an endless amount of matter in it. Consider what I shall call the “Far Universe,” which is all of the infinite amount of matter which is very far away from you, all around on all sides. Though it is very far away, there is an infinite amount, so the gravity it applies to you is infinite. However, because it is all around you about equally, the gravitational pull is basically balanced out.
You can think of the Far Universe like a bubble which is around you, and applies an infinite amount of gravitational pull to you in all directions at the same time, such that all of the gravitational pull cancels itself out and you experience no gravitational pull from the Far Universe. As far as you are concerned, you are at the centre of the Far Universe, since it is defined around you, and thus are balanced at equilibrium, and are not moving.
But what about an item a ways to your left? Let us say, a rabbit? It is slightly nearer to the edge of the Far Universe from your perspective, therefore, according to you, it should be pulled away from you, to the left. It should move away from you at an accelerating rate.
Of course, from the rabbit’s perspective, it is at the centre of the Far Universe. It is that much closer to the further left universe, and that much further from the further right universe. As far as the rabbit is concerned, it is in equilibrium at the centre of the Far Universe. However, from the rabbit’s perspective, you are to the right of the itself, and to the right of the central equilibrium which it inhabits. Therefore, the Far Universe should apply to you a gravitational force which pulls you further to the right away from it.
We find that this hypothesis is compatible with observation. Indeed, for any one object, that object experiences all other objects to be accelerating away from itself, while that object experiences itself to not be moving.
When you think of things in relative terms, it all seems to make so much sense. There is no need to posit the existence of dark energy. If dark energy were the case, then the universe would necessarily be accelerating faster in areas of lower material density. There is also no need to modify Newton’s laws. Indeed, the acceleration of the universe follows naturally from the assumptions we intuitively make about the universe, just so long as we consider things relativistically, just as Einstein did with things like the speed of light, size, and simultaneity.
I am of course by no means in a position of sufficient expertise in this field to try to press this forward as a serious hypothesis, but it nevertheless seems like it could be reasonable enough from what I understand of the universe. What are your thoughts? (If it is confusing the way I have written it, let me know if you’d like me to try rewriting it in a clearer fashion. Maybe I could focus more on diagrams.)