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Milky Way Is Being Pushed Across the Universe (cnn.com)
dryriver quotes a report from CNN: Our home galaxy, the Milky Way, is being pushed across the universe by a large unseen force, according to new research. Although it may not seem like a friendly gesture, the newly discovered Dipole Repeller is actually helping our galaxy on its journey across the expanding universe. Researchers have known that the galaxy was moving at a relative speed for the past 30 years, but they didn't know why. "Now we find an emptiness in exactly the opposite direction, which provides a 'push' in the sense of a lack of pull," said Brent Tully, one of the study authors and an astronomer at the Institute for Astronomy in Honolulu. "In a tug-of-war, if there are more people at one end, then the flow will be toward them and away from the weaker side." But this is no aimless journey of motion. Researchers have long believed that our galaxy was attracted to an area rich with dozens of clusters of galaxies 750 million light-years away, called the Shapley Concentration or Shapley Attractor. "We found a flow pattern reminiscent of streams of water that are organized by gravity to run downhill," Tully said. "In detail, we played a mathematical trick by inverting the sense of gravity to see where flows would terminate in this altered case. Flows ended at our Dipole Repeller."
If I understood this right they are calling the lack of attraction, repulsion. There's no negative force, or dark energy style shit involved. Shouldn't they call it a non-attractor unless they show active repulsion? If I drop an object and it moves towards the ground I am not going to say my hand repelled it.
I think space itself is some kind of medium and not necessarily matter based. Currently, its composition is unknown. You can call this medium aether if you like, just do not confuse it with the luminiferous aether. There are several aether theories out there, one of the popular ones is the Superfluid Vacuum Theory.
Now, back to gravity. We know since Einstein that matter curves/disturbs space**. So, this medium, which is disturbed by matter, wants to be 'smooth' and it exerts a force on matter. This force is obviously a push force and we call it gravity.
From our perspective there is no way to differentiate between pull or push. Maybe until now.
** I know that according to GR gravity is a curvature of space-time and not just space. But if space itself is some kind of medium then the time dimension simply does not exist. What happens is that the disturbance of space prevents matter particles to interact with each other. We perceive this lack of interaction as if 'time' slow down since there is no change (We can only perceive 'time' by observing change). This picture is compatible with GR since relativity between moving bodies through space remains. However, it establishes a distinguished reference frame which is space itself.
Government cannot make man richer, but it can make him poorer. - Ludwig von Mises
The approach being used that identifies the repulsor is a valid one. Bicycle mechanics have been using it since at least 1890 in practical work.
When truing a bicycle wheel, it makes sense to talk about the push that a spoke exerts against the ground that keeps the wheel from collapsing. While you cannot push a string, the tensile pulling forces of all the spokes toward the top of the wheel are too complex to easily analyze. But fortunately it works out that you can invert your frame of reference and then not worry about those forces since in the inverted framework those tensile pulling forces become a single push through the one spoke that opposes the sum of the vectors of all the other spokes.
A miniaturized bicycle mechanic standing on the inside surface of a wheel's rim could use this pushing vector to figure out where the hub of the wheel was. That is never done only because bicycle mechanics are big enough to eyeball the entire wheel. But scale the metaphor up....
That is what is being done here. It is an interesting study, and much more than a theoretical sleight of hand. It suggests that the Milky Way is moving away from a specific point, which they are calling the "Dipole Repulsor", but which can also be described as the Center Of The Big Empty. I did not see anything in the article that suggests that we know how far away the COTBE is, but it looks like we at least know its direction from Earth, the Solar System, and the Milky Way. That's more than we knew before.
It has long been understood that the universe is expanding like the surface of a balloon that is being inflated. This work suggests that we may now know the direction to the center of the (possibly local) universe. I'm not entirely sure of the scale of the implications... this could be on the scale of the Copernican Revolution.