Australian Study Backs Major Assumption of Cosmology 94
cylonlover writes "In mankind's attempts to gain some understanding of this marvelous place in which we live, we have slowly come to accept some principles to help guide our search. One such principle is that the Universe, on a large enough scale, is homogeneous, meaning that one part looks pretty much like another. Recent studies by a group of Australian researchers have established that, on sizes greater than about 250 million light years (Mly), the Universe is indeed statistically homogeneous, thereby reinforcing this cosmological principle."
Re:Aliens? (Score:5, Informative)
(and, shouldnt that be a unit of volume, not length?)
When talking in terms of scale, it's generally better to use fundamental units, not derived ones. Volume is derived from length (length^3), so a volume scale is inherently a length scale, but less precise. If you were to use a volume scale, say 250Mly^3, then that could mean different averages looking in different directions (i.e. the universe is homogenous every 250kly looking up, every 10ly looking left, and every 100ly looking forward). Just using a length scale ensures all 3 dimensions are covered equally.
Re:Aliens? (Score:3, Informative)
So, does that mean there is atleast one Earthlike planet with life on it every 250 million light years?
No. Statistics don't work that way. It might mean there is, on average, one Earthlike planet per given volume of space, but certainly no "at least" guarantee, and indeed if the average is that low, there will be many instances of zero in said volume.
Re:Aliens? Probably. (Score:4, Informative)
More to the point would we recognize intelligent life even if it was in front of our face.
Re:Aliens? (Score:4, Informative)
There's a reason that we use volume as a dimension......volume doesn't depend on shape.
There's a reason that we don't use volume as a measure of scale - volume doesn't depend on shape. That's my entire point. When you're dealing with scale, it doesn't matter if it's a sphere or a cube, because we're dealing with statistical averages, not defined physical limits. The difference between a sphere and a cube of D=S is dwarfed by the difference between a sphere and a hugely-eccentric ellipsoid of equal volumes. The point is homeogeneity. We want to be clear that the average pointing one direction is the same as the average pointing another direction. You can't do that with volume.
Re:the idea that it loops and we see old stuff-- (Score:4, Informative)
It was pretty much ruled out by the cosmic background microwave radiation surveys. Because that's a point-in-time snapshot of the universe, seeing the same stuff repeated in layers would really stand out. The visible universe is a subset of the universe.