goat37

I have been reading many books on astrodynamics, thermodynamics, and other books on physics... Most recently being "The Elegant Universe" by Brian Greene.

In reading about the Big Bang, and Black Holes (I am sure this has been thought of, but not been able to find anything on it) a theory dawned on me, that I have been yet able to disprove (due to the limited info we have on black holes, and the big bang alike)

In Hawking's "A Brief History of Time" he talks about Hubble's observations that led him to the thinking there was a point that the universe began or 'big bang'. This was when the universe was infinitesimally small and infinitely dense.

Now, take that thinking over to what we think we know about Black Holes... Which nothing (including light) can escape. What is generally believed that at a bottom of a black hole is what is knows as the 'singularity' where all matter, energy, etc... that it takes in, is turned into one single infinitesimally small and infinitely dense point.

It is widely believed that black holes exist at the center of most galaxies (including the milky way) and are growing. Add to that more black holes being created after massive stars go supernova and finally collapse. With black holes expanding and being created, along with the fact that matter cannot be created (nor destroyed), can one conclude that at one point in the mathematically exponentially distant future, that all matter and energy in the universe be consumed by black holes? And after that, would the black holes not consume each other creating 'one' singularity?

If that can be done, would you not essentially have the makings for a 'big bang"? You would have one infinitesimally small and infinitely dense point that includes everything that ever existed?

So in conclusion, could this not be taken to assume that we may not be existing in the 'first' universe, but rather be existing in one that had been 'recycled' so to speak?

I know this doesn't give any insight to the "original" creation of the universe, but it is something that I have been thinking about for a while... any help on where I may gather further information would be great, or if you have any input or insight, I would greatly appreciate it.

Bnonn

No. Two reasons.

Firstly, black holes are a form of energy (curvature of spacetime). They eventually die because they are not perfectly black; they emit Hawking radiation. Therefore, since all black holes eventually die, there will be no future with huge numbers of black holes sucking each other up (or more likely combining into larger singularities; I don't pretend to understand the math involved). Instead there will be a gradual heat death as energy gradients progressively flatten until there is no more energy differential between different points in space (remember that the universe's total internal energy sums to zero).

The second reason is more obvious. Black holes suck in matter-energy. They don't suck in the other half of the equation, which is spacetime. The big bang spacetime itself, not just matter-energy. Black holes are a distortion of spacetime, but they do not suck it in per se. So even if the universe did end in a single, huge black hole, there would never be a circumstance where it could cause another big bang.

Majestyk

Bnonn, could you elaborate on the death of Black Holes (a singularity)?

Bnonn

This page explains it fairly well (it's the first link I found on Google).

Basically, if you don't want to read all that, black holes emit very faint radiation in the form of photons. This is known as Hawking radiation. The Hawking radiation comes from the formation of virtual particle pairs in space, where one particle escapes the event horizon before it can be annihilated again with the other particle. This causes the black hole to slowly lose energy (and I do mean slowly; a black hole with the mass of a mountain would take the current age of the universe to evaporate). Eventually, all its energy is radiated away, and it evaporates.

Of course, as long as a black hole has something to suck in, it will not evaporate. It is only when it is receiving no input of matter-energy that it will start to degrade.

Undercurrent

It's important not to take the "singularity" in the centre of the black hole too seriously. "Singularity" is a mathmatical term, not a physical one. In any other branch of physics, a singulariuty in a solution to an equation is interpreted to mean that the assumptions of the model break down at that point, not that there is actually a "real" singularity in the real universe.

fando

Right. It's important not to confuse the model (General Relativity and its 'absurd' singularities) with physical reality. When Hawkings describes to us the nature of the universe, he is actually presenting a particular theory that he fancies as the real thing. Whether it's true or not is open to scientific observation and experimentation.

Bnonn

Why do I have the feeling I've been set up somehow?

nermal

Let's not forget that while the density of the singularities approach infinity, their mass cannot exceed the mass of the matter which has composed them, therefore, a black hole which "eats" a galaxy will not be more massive than the galaxy, and will not exert a greater gravitational force than the combined mass of the galaxy itself.
Couple that with the fact that the expansion of the universe is accelerating, and the compression of galaxies into black holes will not change that (see above) then you still get heat death.

Ed

Shake

What I got out of the linked article that Bnonn points us to, is that were the Universe not expanding, something like the o.p. hypothesis could happen since, according to the article, it takes so long for supermassive black holes to evaporate. Only the smallest holes would evaporate somewhat quickly. But, given that current theory postulates that we are in an expanding Universe (without enough matter for a 'Big Crunch' to happen), the implication is that the Universe will become a very cold, basically empty, homogenous space, expanding forever.

At least that's what I understand. I also have The Elegant Universe, but I don't think I've read it yet. I have read some Hawking and some of Kip Thorne's work such as this.