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> dropping the fairly convincingly invalidated assumption of large scale uniformity in the mass distribution of the universe. The problem with that is then you

by bsder 2y ago

> dropping the fairly convincingly invalidated assumption of large scale uniformity in the mass distribution of the universe. The problem with that is then you need a mechanism that creates non-uniformly distributed mass. Otherwise, you are simply invoking the anthropic principle: "The universe is the way it is because we are here."

zmgsabst 2y ago
You don’t need a mechanism to point out a fact contradicts an assumption, eg, our measurements show non-uniform mass at virtually all scales (including billions of light years). There simply is no observable scale with uniform mass. Obviously there’s some mechanism which causes that, but the mere existence of multi-billion light year structures invalidates the modeling assumption — that assumption doesn’t correspond to reality.
- throwawaymaths 2y ago
  yeah the ~1b ly nonuniformity is pretty much there. the ~10b ly uniformity is still early days but looking more and more likely as more data roll in (unless there is a systematic problem)
marcyb5st 2y ago
I think that can be mitigated in three ways: our understanding of inflation is flawed, there were more "nucleation" sites where our universe came to be, and there are the already theorized baryonic acoustic oscillations that could introduce heterogeneity in the universe. Maybe is a combination of these, maybe something else. If nothing else, the uniformity is less probable than a mass distribution with variance (unless there is a phenomenon like inflation that smoothen things out, but also that was introduced to explain the assumption of a homogeneous universe). I concede that explaining the little variance in the CMB with our current understanding is hard when dropping homogeneity assumption however.
jcarreiro 2y ago
> The problem with that is then you need a mechanism that creates non-uniformly distributed mass. The mechanism is gravity; and we have good observational evidence that the mass distribution of the universe is not uniform, at least at the scales we can observe (we can see galaxy clusters and voids).
throwawaymaths 2y ago
> The problem with that is then you need a mechanism that creates non-uniformly distributed mass. you need no such thing. thats like saying "i refuse to acknowledge the pacific ocean to be so damn large without a mechanism". you dont need that. it just is. this doesnt preclude the existence of such a mechanism. but for any (legit) science, mechanistic consideration should be strictly downstream of observation.

by bsder 2y ago

zmgsabst 2y ago

You don’t need a mechanism to point out a fact contradicts an assumption, eg, our measurements show non-uniform mass at virtually all scales (including billions of light years). There simply is no observable scale with uniform mass. Obviously there’s some mechanism which causes that, but the mere existence of multi-billion light year structures invalidates the modeling assumption — that assumption doesn’t correspond to reality.

throwawaymaths 2y ago
yeah the ~1b ly nonuniformity is pretty much there. the ~10b ly uniformity is still early days but looking more and more likely as more data roll in (unless there is a systematic problem)

marcyb5st 2y ago

I think that can be mitigated in three ways: our understanding of inflation is flawed, there were more "nucleation" sites where our universe came to be, and there are the already theorized baryonic acoustic oscillations that could introduce heterogeneity in the universe. Maybe is a combination of these, maybe something else. If nothing else, the uniformity is less probable than a mass distribution with variance (unless there is a phenomenon like inflation that smoothen things out, but also that was introduced to explain the assumption of a homogeneous universe). I concede that explaining the little variance in the CMB with our current understanding is hard when dropping homogeneity assumption however.

jcarreiro 2y ago

> The problem with that is then you need a mechanism that creates non-uniformly distributed mass. The mechanism is gravity; and we have good observational evidence that the mass distribution of the universe is not uniform, at least at the scales we can observe (we can see galaxy clusters and voids).

throwawaymaths 2y ago

> The problem with that is then you need a mechanism that creates non-uniformly distributed mass. you need no such thing. thats like saying "i refuse to acknowledge the pacific ocean to be so damn large without a mechanism". you dont need that. it just is. this doesnt preclude the existence of such a mechanism. but for any (legit) science, mechanistic consideration should be strictly downstream of observation.