Yes, clickbait. The "invisible force" here is gravity.
This is the key bit of context:
> When describing the gravitational dynamics in co-moving coordinates, by which the expansion of the Universe is factored out, underdensities repel and overdensities attract.
So it's basically a coordinates transformation thing.
Upon reflection, Hoffman et al. (2017) itself may arguably be clickbait. To the extent that I understand it, they're looking at inhomogeneity in cosmic expansion. It seems equivalent to turbulence in fluid dynamics. That is, non-uniform flow.
And in considering airflow, for example, one doesn't say that underdensities repel air, or that overdensities attract air. Rather, it's the non-uniform flows that create the underdensities and overdensities.
Anyway, it seems to me that Hoffman and coauthors should have stuck to describing correlations, because that's all they have. Using the language of causality is confusing. They don't mention it, but maybe they have an agenda to promote varieties of dark matter with positive and negative gravity.
> Oh, I see. The title of the HN submission has been creatively edited and is not the title of the original Nature article.
Well yeah, they seem to have put it into laymans terms, but as a layman it appears to be an accurate representation of the article. It's certainly more descriptive than "The Dipole Repeller", so not click bait.
Yeah, its about the motion of our Local Group, but yes. Here's the summary provided in the xml:
>The presence of a large underdensity, the dipole repeller, is predicted based on a study of the velocity field of our Local Group of galaxies. The combined effects of this super-void and the Shapley concentration control the local cosmic flow.
Yup, saying invisible in there was redundant. That's not all, though. Saying force is additionally also redundant too. All things pushed around are pushed around by force.
"Milky way pushed around" would have been sufficient to convey the interesting part. It's interesting because at galactic scale isn't it usual to be pulled around rather than pushed around?
Oh, I see. The title of the HN submission has been creatively edited and is not the title of the original Nature article.
Clickbait.