Originally Posted by Justin1982
Damn funny thread.
Shape of the universe and the supposed "edge" of the universe are difficult things to get ones head around.
It depends on what you think the universe is.
A good book. Lawrence Krauss A Universe from Nothing: Why There Is Something Rather than Nothing. Though I have to give it a better read - I don't own a copy.
Before Lemaître and Hubble, the milky way was considered to be the universe. Even Einstein said something to Lemaître along the lines of "Your math is correct, but your physics is abominable."
The idea of the steady state universe didn't die until Penzias and Wilson finally put a nail through it in 1964.
Krauss's thesis, which I believe is the conventionally accepted one at this point in time, is that our universe, all the stellar material from the big bang, was formed by a quantum fluctuation of empty space. Krauss says in his book, that space could be filled with universes like our own.
So if the universe is something where something can happen - then the entire universe is endless. And it's mostly endless nothingness.
Incorrect Version that permeates popular science:
Universe exploded from a singular point and expanded out from that point at the speed of light and the edge of the universe is now ~14 billion light years away from us here on earth.........This is false!
You know there are several Yellow Submarine type explanations of the shape of the Universe. One, that I think is attributed to Einstein, is that if you walk any direction in the Universe you'll eventually come back to the same point - I don't know whether that's due to gravity bending space, and looping you back to where you started or if it's like Nietzsche eternal return. Other definitions I've heard, material can travel in whatever direction it's travelling in and never come back to the same point.
A thing about popular science writing, is you're going to see ideas that are known to be wrong for a long time - and you'll see them especially garbled. Like writings on black holes. The most common misconception you'll see written about black holes, is that if you were approaching one, you wouldn't see it. But according to Einstein you'll see gravitational lensing - space being bent around the hole - and according to Hawking, you'll see a lot of light. A giant spinning black hole would probably be the most spectacular sight in the universe. Centre astral objects we can see, appear to be that.
In popular writing you'll see stuff like, as you approach a black hole you wouldn't see anything, and then you'll get turned into spaghetti, but you won't notice this as you'll be frozen infinitely in time. Or you'll see something like, a black hole is an infinitely tiny point in space with no radius.
Black holes are wonderfully mind bending. Like Hawking's photons. Can they be entangled if one is behind the black hole horizon and the other isn't. What about superposition and black holes.