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 Originally Posted by rong
I mean the big bang sounds like a star imploding/exploding/whatever we call the creation of a black hole
... except that the Big Bang involves ALL of the stars, black holes and everything in the universe (even all the space and time) existing in a volume smaller than a single proton. There really is no comparison to any other kind of explosion or expansion.
A Black Hole is a region of space-time in which the gravitational energy well is too deep for anything to escape, even photons. Generally, they are formed by the core collapse of a massive star. Sometimes, 2 objects can collide to create a black hole. Also, an object that is nearly massive enough to be a black hole can become a black hole by accretion, the gradual gathering of mass from a nearby object.
There is also some evidence for primordial black holes, or black holes that formed in the early universe and were kind of the planted seeds for galaxies and eventually star formation.
So far, every galaxy observed (lol only 1, the Milky Way) has a super-massive black hole at its center.
Originally Posted by rong
and the universe expanding sounds like it fits the theory of a black hole sucking stuff in as it grows.
Black holes do not "suck stuff in as they grow"... except when they do, of course.
General Relativity tells us that mass curves space-time creating the illusion of a gravitational force. The force is an illusion, because objects move in straight lines at a constant velocity through curved space-time. Since only an object which is not being acted on by a force will move at a constant velocity in a straight line (Newton's 2nd), the "force" of gravity is an illusion cause by a human limitation in "seeing" the curvature of space-time.
E.g. if the sun were instaneously replaced with a black hole of equal mass, the planetary orbits would be unaffected.
All of that is to say, it is the mass of the object, and not its composition, that defines how much it sucks.
ALSO: Black Holes radiate profusely, by Hawking Radiation, which makes them not-so-black after all. It means they slowly shrink over time.
In other words, it really sucks to be inside them, and it kind of blows to be near them.
IF a black hole collides with a star or other massive object, then obviously, the resulting object is more massive than the original black hole, so it would have a "growth spurt" (I made that up). So, technically, they do "suck stuff in" and "grow" but it's not like they're the Hoovers of the universe.
Another point is that the black hole would be expanding because of "stuff" "coming in" from the "outside". Whereas, the universe is expanding because "space" is "spontaneously expanding" "everywhere".
Originally Posted by rong
This may be a dumb question as I know nothing on this subject whatsoever. But is there any evidence to suggest our universe is not the inside of a black hole. [...] Is this not the most obvious theory of our universe? Does anything prove/imply/suggest that this isn't the case?
There is just no basis for a physicist to answer this. Physics answers questions about observable things, and the inside of a black hole can not be observed by definition. So physics is simply not equipped to answer this as of now.
I mean... the way to answer it would be:
What are the implications/predictions of your theory?
Can any of those be measured?
If yes: Well, go on and measure that and see if the data support or refute your theory.
In no: Sorry, this is not science.
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