If Space Wasnt Infinite

.

 

Correct. The Big Bang is one example of a singularity. In the traditional model of black holes, they're the "center," the point of infinite density.

 

Im not sure that a black hole has a singularity at the centre. I cant see why theres any good reason for a black hole should have a singularity at the centre. A black hole is just a very dense heavy object, nothing more nothing less. However to understand what goes on the in the middle is difficult this is because there are intense gravitational fields over short distances. This means that a quantum mechanical description for gravity is required. General relativity and QM have made some predictions about the edge of black holes such as Hawking radiation. However the middle is very much a mystery. Maybe are just a interesting mathematical idea, or perhaps they exist. My personal opinion is that the conditions at the moment of the big bang approximate to a singularity but I suspect it still had dimensions, just very small ones.

 

I disagree. It is fundamentally different than most other objects, because it is SO dense that gravity overwhelms the nuclear forces, and there is nothing else (that we know of) to stop the object from collapsing into itself until it is infinitesimally small.

The reason supergiant stars exist is because the nuclear force more or less counters gravity. Once they exhaust their nuclear fuel, there's nothing left to fight against gravity and if they're massive enough they can collapse into a black hole.

But like you and Shaggie have said, we won't know for sure until we have a quantum theory of gravity.

 

If all else fails theres the fermi exclusion principle, although that would hold as long as quarks hold. The region at the centre of a black hole is called a singularity, in black hole terms this is defined as the region of a black hole where known physics breaks down. As far as I know this region can be a very finite size. Things like the fermi exclusion principle come to my mind but how this comes into pla in quantum gravity i have no idea.

 

Ive been doing some searches on this and it seems the answer is not clear cut. Some seem to suggest that a black hole has to have something approximating to a singularity within it. Others seem to suggest that its a region where known physics breaks down and what actually happens is anyones guess. Personally Ill settle with the gravitational potential is huge and it will collapse to a very small point.

 

do you think blackholes could be considered "rips" in space-time? or is there actually a dense center within? i always thought that blackholes there just like vortex type things where matter went in and dissapeard. i get this image because when i hear "physics as we know it breaks down" i think of a place outside of this universe.

 

If Einstein's model of black holes is correct, then yes, you can view a black hole as a rip in space-time and it would be vortex-shaped.

However, there is also thought to be a point of infinite density (until a quantum theory of gravitation proves otherwise) called a singularity.

Matter doesn't necessarily disappear forever once it goes into a black hole though. Stephen Hawking has shown that black holes can "leak" matter and energy over long periods of time.

 

A rip in space time is hard to picture for obvious reasons, but ill have a go. If you take a flat soft object like a matress and put something heavy, like a snooker ball, on it you will get a dent. This is the effect a mass has on space-time, it is perfectly acceptable to think of anpther object falling into this dent as gravity pulling in another object. In a black hole this dent becomes so deep and steep sided that the velcoity required to escape is faster than the speed of light. A singularity or rip in space-time is where this dent becomes a bottomless pit, the matress develops a hole (or a rip in space time).

Everything being pulled into a gravitational potential must have a countering force to stop it collapsing in on itself. What stops us disappearing into the earth is the fermi exclusion principle, this says that two electrons cannot occupy the same quantum state, the upshot of which is that two objects stop when they hit each other. In a star it is the pressure of the nuclear reaction that pushes against gravity. The quesiton is in a black hole is there any force that can counter the intense gravitational pull? The densest objects apart from black holes are neutron stars, here objects heavier than the sun have radii of 20km. Electrons and protons can be fused into neutrons, so the exclusion principle I talked about no longer keeps them apart also there is little radiation being produced, so the star collapses to a dense ball of neutrons. However at this point the exclusion principle comes in again, as neutrons obey it, so the netrons are forced apart with a force strong enough to counter gravity. The escape velocity from a neutron star is around half the speed of light. If the object is too dense to be halted by this force it becomes a black hole. Is there another law that prevents an infinite collapse, my hunch is there is, but no one knows. This is where the physics breaks down comes in. Quantum mechanics describes the very small and all forces apart form gravity. General relativity describes the very big and gravity. These two theories refuse to unite, this essentially what superstring theory is trying to do. Until this is solved then to decide if there is a singularity inside a black hole, roll a dice. Even people like Stephen Hawking have gone one way then the other over the past few years. Hope that clears it up, or at least clears up that we cant clear it up.

 

so what would you say is the difference between a blackhole with singularity and the big bang? whats to stop a blackhole from "spawning" another universe? was the big bang just a black hole but on a greatly larger scale?

 

Conservation of energy is a conerstone of physics and a black hole can contain no more matter than what has gone into it. Therefore it will always be much smaller than the big bang even if its structure turn out to be similar in principle. Also a black hole will evaporate given time, a long time, but it will. Quite why a black hole evaporates and the big bang exploded in such style im not sure. But I think some people are saying that the big bag occured as part of a collision in a higher dimensional space. But this is getting very theoretical with absolutely no experimental basis at all.

 

do you think the fact that blackholes simply evaporate over time could make one rethink the whole bigbang theory, or are scientists firm in their beliefs that it was indeed a "bang"?

 

Its just a theory its not a law, so scientists could change the way they think, a few centuries ago, people KNEW the earth was at the center of the universe, that changed. There is a great book, called "The BIg Bang Never Happened" and it says the universe has just always been and is constantly evolving. The book is pretty good whether you support the big bang theory or not.

Just thought I would put that in here

 

Even that black holes evaporate is a contested theory. My understanding is that Hawking (who originated this theory) has expressed some doubts about it more recently.

As far as the big bang goes, there are a few competing theories out there presently. One of the interesting ones is a "fractally inflationary" universe, in which 'big bang' like events can happen in various regions, but there may never have been an actual beginning.... they wrote about that one in Scientific American a few years back. It's not in vogue, but there are non-big-bang options out there that meet the present observations.

 

I haven't studied it enough to be able to knowledgeably defend or refute the theory, but here's the way black hole evaporation works as I understand it:

Black holes have what is called an "event horizon." This is the point of no return; once you cross the event horizon of a black hole, the force of gravity becomes so strong that not even light can escape.

Also, particles and antiparticles routinely pop into existence from nowhere (always in pairs), but almost always collide and annihilate each other a fraction of a second later. Theoretically, if the particle/antiparticle pair formed right at the edge of an event horizon, one of them might be sucked into the black hole while the other would not be. Thus, for all intents and purposes the black hole emitted a particle! The law of conservation of matter provides something of an exception for quantum particles (Matter and antimatter CAN be created...but only for small fractions of a second before they annihilate each other). Since the "escaped" particle is not annihilated and the "doomed" antiparticle is lost to the outside world forever, you have to balance the additional mass of a particle to the outside world with the subtraction of an equal mass of an antiparticle in the black hole.

Since particles tend to be very small and black holes tend to be very massive, it would take an immense amount of time for a black hole to evaporate...many orders of magnitude longer than the current age of the universe.

I'm not sure if I'm explaining that correctly, or even if it's a practical theory. It seems to me like that is just mathematical equivocation. It seem like the fact that the Law of Conservation of Matter SAYS that you should subtract the mass of a particle from the black hole, doesn't change the fact that there's actually an additional particle there. But like I said, I don't know enough about the theory to make an informed judgment on it.

 

.

 

.

 

Wow. That is really weird.

 

I do like the idea of quark stars, it fits very nicely into current theories. If theories about neutron stars are correct then id go as far as to say that a quark star should be expected.

 

the universe isn't infinite. my brother (who taught me everything) was telling me about this book he was reading, and the universe is like 1 with like a LOT of 0's lightyears across. i'd have to talk to him and find the book. but i was completely confused, because in space theres no air, just nothing, so beyond the universe wouldnt there be just nothing? which would mean it doesnt stop... im not sure if im making any sense. but i think if it had to stop there would have to be a wall or something. maybe it'd like that Men in Black movie where the cat has a whole universe around its neck. and maybe on my fingertip, or in my blood cell are millions of universes. its mindblowing to think about. i wish i was smarter