The thread on the expansion of the Universe reminded me that I don’t understand why we have stars, planets, plants…or politicians. :smack:
If we took a ball of flour and exploded it in a vacuum, would flour asteroids occur? Miniature suns? I suspect not.
So we have the Omega point at the Big Bang. Proto-particles expand outwards as the Universe is born. Why did some particles form into clumps instead of floating free of each other?
Space is lumpy because it started out lumpy. Why did it start out lumpy? Because of inflation (see third paragraph down, which also includes this link).
Basically, quantum fluctuations created an initial anisotropy. Sort of like how when you explode a ball of flour, the flour particles are not equally spaced. As they spread out, the gravitational attraction between the closer bits of flour will cause them to begin to lump. Once they begin to lump, the lumps are not equally spaced. The lumps begin to lump. And so on. If you exploded a large enough ball of flour, this would happen, and you could have suns, although they would be pretty shitty short-lived suns due to having too much carbon and not enough hydrogen fuel.
Thanks for that. I’m trying to understand the linked articles…but my cat keeps walking on the keyboard.
I do know of the hyperinflation of the Universe but don’t pretend to understand why it occurred. Your point that particles won’t be uniformly distant from each other makes sense although I suspect the rationale lies with quantum uncertainty. Is that correct?
Good, because no one knows why it occurred. This is an unsolved issue, likely because we don’t have an theory of quantum gravity yet.
Yes.
If the universe is constantly expanding, how would galaxies ever cross paths?
And, as the universe grows, the interstellar stuff gets thinner and more widely dispersed-how does agglomeration occur?
From my understanding depending on the locations gravity over powers the expansion.
From my recollection, there’s also a link between the maximum size of the “lumps” in the universe and the speed of light; since gravity is not instantaneous but works at light speed, objects that were “created” at the big bang can only gravitationally attract if the distance between them is less than the age of the universe (so when the universe was 1 year young, particles that were more than 1 lightyear apart could not attract).
Lawrence Krauss’s fascinating talk “A Universe From Nothing” touches on this issue.
Space is lumpy? To me, it seems more stringy than lumpy.
counterpoint: the word “cluster” is used a lot in that linked pic 
On the cosmological scale, galaxies are tiny. The expansion of space is negligible across the width of a galaxy cluster.
I knew I was on to something when I was blowing bubbles in my chocolate milk!
In a gravitational sense, yes. You would have bodies orbiting other bodies given enough time and a vacuum to float freely in.
Believe it or not, the distribution of galactic superclusters seems to be based on the same scientific principle.
Very helpful links thanks. One of the curious observations about the Universe (which deserves uppercase IMHO :D) is that we see clusters, bubbles if you will, of matter. These are separated by vast empty areas, and the clumps occur within notional membranes. Or “branes” as they are sometimes referred to. Which somehow leads to string theory but as a non-mathematician that’s beyond me.
Almost counter-intuitively the Universe for us is homogeneous - the same general distribution of galaxies whichever way we look. Only…those galaxies are actually in membranes and there are incomprehensible empty distances between the groups.
So while the sky is very busy out to 13.7 billion light years, the busy-ness is not spread evenly. It clumps.
I blame Schrodinger’s cat…
Clearly, because it has not been properly stirred.
You’re getting two completely different concepts mixed up. The “membranes” along which galaxy clusters are arranged are (roughly) two-dimensional surfaces in our Universe, and you can see them directly and make models of them out of bits of plastic and the like-- Nothing weird at all about them. The “branes” in the String Model, though, are three-dimensional, and our entire observable Universe is all in a single brane.
