We might be living in a gigantic, intergalactic bubble


Oct 22, 2019
The bubble concept could explain one of the strangest mysteries plaguing astrophysics: Why can't we tell how fast the universe is expanding?

We might be living in a gigantic, intergalactic bubble : Read more
The report and cited shows our region of space some 40 Mpc density may feature a bubble that helps reconcile the different measurements for H0, the Hubble constant as measured from Earth. Is this solution a departure from the Copernican principle?

The cited paper says "This work presents an estimation of the likelihood of residing in a sufficiently underdense 40 Mpc environment to give rise to the observed discrepancy between the measured local and cosmological Hubble constants."

Very interesting in view of the Copernican principle in cosmology. Next, the Earth may indeed be at or near the center of the expanding universe :)
Jan 28, 2020
I suppose this is where philosophy enters the conversation. I personally don't see this as the earth residing in some privileged place in the universe, just perhaps in one of many large-scale slightly heterogeneous areas that deviate from the idealized cosmological principle of a perfectly homegeneous and isotropic universe. But we could just as easily have found ourselves in a higher-density region, or at the edge between higher- and lower-densities regions, or anywhere in between. If anything, I'd say this is more evidence in favor OF the Copernican principle; we know slight heterogeneous regions exist, and it's just statistics that resulted in us being here vs somewhere else with slightly difference average mass-density, perhaps enough to "flavor" our measurements of H0. Akin to Copernicus observing that retrograde planetary movements make more sense if we disregard the prevailing geocentric viewpoint, this study suggests that we might not be seeing the universe from a totally average mass-density region and that is having a subtle but real impact on some of our empirical measurements. So, from my view, it's not a revising of the Copernican principle at all, but the exact opposite! It's just perhaps bad luck for us to be (apparently?) deep enough in a low-density bubble that it's identification (if true) took until 2020 to happen. :)