Why didn’t the Universe become a black hole?
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And I'm sorry, but this explains NOTHING. Even for moving mass the density was enough to make a black hole.
So presumably the density never actually got that high, or there is some other explanation we are not aware of.
He should have just said: We don't really know. Because we don't. Why is there this requirement that science be able to explain everything?
Is it because it's held up as an alternative to religion so people are petrified that if there are any holes people will say "sciences knows nothing, back to religion"?
(Now that I've setup my strawman I'm going to knock it down.)
First of all Science and Religion are not competing for adherents. You can believe that God created the universe and still want to investigate how he did it, and what the details are. Even if you believe the Big Bang never actually happened (i.e. it's an off-camera backstory), you can still be interested in investigating it because if God made it look like that then it's important.
Second the whole point of science is saying "I don't know", otherwise it's a religion, not science.
density don't need to be high to get a black hole - the more the mass the less its minimal density has to be when black hole can be formed - the Schwarzschild radius of our Universe (which is mostly space with the specks of matter) is on the scale of 10B+ light years for example. So depending on how it is calculated and a lot of other stuff - we still can be inside expanding black hole :)
But if you add dark matter, could that push the Schwarzchild radius of the universe to 13B light years? That is, to the (observable) radius of the universe?
If so, then is it possible that the red shift of distant objects is a black hole effect (remember that in this scenario, we're inside the event horizon), rather than due to the expansion of the universe?
Would this also explain dark energy? It would require that red-shifts in a black hole be non-linear in distance, which I think is plausible, and that they be non-linear in the right direction, which I don't know enough to say anything whatsoever about.
Well, in abstract no. But then again, they are the result of people practicing them (science or religion), and those do compete for adherents.
You are making an assumption here that is debatable. We understand very little of the physics close to the Big Bang. Those scales in energy, time and space are so extreme that quantum effects are expected to be dominant. However, all theory about black holes uses general relativity, which does not account for such scales. It is still an open problem to unite quantum physics and general relativity (i.e. this is basically what string theory hopes to achieve).
> And I'm sorry, but this explains NOTHING.
I think the point is that the assumption made to derive the theory about black holes from general relativity are just not met. The Schwarzschild radius is not defined for non-static spacetime, so it does not apply here.
It is true that it explains nothing, but it also means that you cannot use the Schwarzschild radius in your argumentation.
This image tells it all: https://d262ilb51hltx0.cloudfront.net/max/953/1*QXypiHUwjJZr...
What he was saying is, if there was just 1 gram per cubic cm less mass in the original universe, then it would expand too quickly to form any complex structures and the universe as we know it would not exist. And if it was just a few grams per cubic cm more massive, then it would collapse immediately as in the original question.
The reason our universe did not immediately collapse is not a mystery. It was a tiny amount less massive than would be required for such a collapse.
The reason it was perfectly on the line is no mystery whatsoever: if it were one gram over, it would collapse, and we would not exist, and thus we would not be asking the question. Same if it were one gram less; the universe would be too sparse for life to organize.
This is not a miracle or a mystery, it's simply fact. Billions or trillions of universes might have sprung into existence over billions or trillions or perhaps even infinite aeons of time, each with different masses and parameters of physics.
The one that produced an observer was observed. That's us, and that's it. No miracle, no mystery.
It's like someone winning a lottery. The chances of a specific individual winning are next to nothing, but the chances of anyone winning are 100%. If a news crew then goes and finds the winner, they will surely find an astounded, surprised, and very lucky feeling person. But the news crew will not be surprised, since their observation is entirely expected and even guaranteed.
Humanity is both the winner and the news crew in this situation, by the simple property of our ability to observe our own existence.
This is called the anthropic principle. It also applies with zero modification to the question of why Earth appears to be such a perfect planet to support human life, especially as we begin to discover that there are literally trillions of planets in our universe. We should not be surprised that we observe the one that happened to have the conditions conducive to the evolution of a sentient observer. But you could be forgiven for feeling very lucky that you're one of them.
> The one that produced an observer was observed.
I wonder if it applies in other contexts, specifically, er, quantum decoherence?
It does not do exponential parallelism by trying many things at once. What it does do is create exponentially many paths, while some of which interfere with one another destructively. When you observe the system, then, some paths will have probability zero even though they have non-zero complex amplitudes associated with it.
Scott Aaronson's "Limits of Quantum Computers" to the rescue: http://www.cs.virginia.edu/~robins/The_Limits_of_Quantum_Com...
I've found that when speaking with laypeople about quantum decoherence, a very common misconception comes from the use of the word 'observer' (see: http://www.imdb.com/title/tt0399877/ ). If you say "A quantum system can be in a superposition until its wave function is collapsed when it's observed.", a layperson can easily interpret that to mean that a sentient being needs to look at and take note of the system for it to count as being observed, when in fact all that is required is that an external particle interact with the system and carry away some information (energy).
There's nothing special about humans (and their ability to observe) in this context.
Only an analogy, of course.
"We" reject other universes because "we" observe this one, and "we" don't observe the others. There may not be others. There could be infinite others. We don't know; we know only what we see, and that's a universe in which we exist. The trait of observation means only that an observer exists. It's a tautology, and does not imply anything else.
This is similar to consciousness (another analogy): you appear to be an isolated observer of the world, when in fact there are over 7 billion others, who also are themselves isolated observers of the world. The fact that you can observe your own existence does not mean you are selected or that any selection process took place that resulted in you specifically. Your consciousness came afterward; your ability to understand it even later.
Consciousness is, in fact, quite common and ordinary. It carries no meaning other than what it is. Ascribing meaning to the trait of one's own consciousness is just a human construct. It is an illusion; a by-product of consciousness itself.
As with the universe. The universe which created us is not special. It's simply the one in which we find ourselves. "Special" is what we might call that, but only from our (limited, tiny, inconsequential) perspective. In the greater reality, it is simply a thing that happened. Other universes with different parameters may have other sentient beings in them with the same dilemma. They are not selected for either; they simply happen to have conditions which resulted in the evolution of beings who can see and think and feebly understand where they are.
The purpose of all this is up to you. The most likely explanation is that there is not a purpose to the conditions from which our consciousness came about. It is likely simply one universe in an infinite number in the unfathomably large and complex—yet simple—reality that is. We may never know what is outside our universe, but that is the reason for its continued study.
Or, as good as any:
“We are a way for the cosmos to know itself.” - Sagan
Why should he say that he does not know when the best accepted theory fits reality almost perfectly on that case? The correct thing to say is that he knows.
Also, if you look carefully enough, we know of no matter that escaped the Universe, as far as we know, it fits exactly the property of the Schwarzschild's black holes.
In practice, how are they not? There are at least 3 major classes of popular religions that claim that the earth is only 6000 years old, among a smattering of other objectively false claims. One cannot correctly claim these facts are or might be true and also observe the scientific method.
Yes, a hypothetical religion that posits nothing more than "there is a god" would not technically directly contradict the known body of scientific knowledge, but it would still contravene the scientific method.
The thing is that while the root of Christianity and science aren't compatible, the everyday practice of Christianity has little to do with that root. It's just some initial justificiation that doesn't really touch the everyday. The congregation are generally not so interested in the philosophical underpinnings than the daily practice. Praying to a saint that can't be proven, lighting a votive candle, or dropping money in the poor box does not compete with investigating atoms.
Yes, it absolutely does, because believing in the truthfulness of that person's sainthood (i.e. the existence of miracles) or the efficacy of prayer as a method of communicating with dead people requires the devotee to ignore scientific evidence to the contrary and/or believe something that has not been empirically deducted or otherwise formally proven. This is essentially the opposite of the scientific mindset.
I hate to be pedantic... wait, I LOVE to be pedantic.
If you consider a human being to be a 50kg bag of water, that's 2750 moles of water, or ~1.7 * 10^27 molecules. Each molecule has ten electrons, so this factoid is off by about four orders of magnitude. More if the person had a big bowl of electrons for breakfast that day.
Just being pedantic!
I also don't like how the discussion at the end was phrased. It started talking about fine tuning and making a mathematical argument as to the chances that our universe would have exactly the amount of mass it does (which I believe makes the assumption that the mass in our universe is random, though it was never stated). The problem with this is it's basically the argument that our universe must have been made by some external entity (i.e. "God"), without actually saying as much. I say this because there's no other good reason to try and make claims about the statistical likelihood of our universe having the initial conditions it did. And of course, it completely failed to mention that of course the universe's conditions are just right for it to have produced stars and planets and eventually life, because otherwise we couldn't be talking about it. There's a pithy name for this, but I forget what it's called. It also failed to mention the trivial solution to getting a universe that's fine-tuned just right, assuming random initial conditions, that doesn't require invoking any kind of supernatural being: infinite universes.
Or perhaps there is an infinite number of Universes and big bangs out there, and ours was just one of the possibilities, while billion other big bangs "failed" in recreating our conditions.
This make the answer far more complex, just to try to avoid the fine tunned of the universe, methinks.
1. We really don't know. We don't understand the rules of physics well enough to model the behaviour of stuff in such "extreme" situations.
2. If you still insist on asking that question, I could give you a plausible explanation of why the question is not really the right thing to ask: "small" black holes tend to evaporate very quickly through the process of Hawking radiation -- in effect producing photons, matter, and every possible kind of "stuff". So even if there was something akin to a black hole, early in the universe, (and if we could apply our rudimentary understanding of gravity and quantum mechanics to even talk about black holes and Hawking radiation) it wouldn't trap the stuff for long... in fact it would be spewing out stuff in copious amounts, and very quickly at that.
But, whatever, it was small, and, most important, that's all there was. There was nothing more. It was not a very dense, very hot chunk of matter-energy, whatever, inside some larger space. Instead, that's all the space there was.
Then the OP is saying that in that context, where the whole universe was just that ball, the old arguments on forming a black hole don't hold. Instead, what happened was, space itself, that is the whole universe itself, explosively expanded. And it's still expanding.
So, what was that universe 'inside' and what has it been expanding 'into'? Either these are poorly posed questions, or we don't know, or, for the question in the OP, it doesn't matter.
Maybe that's what was going on in the OP. Maybe.
If we had the ability to alter the fabric of spacetime, could we shrink that fabric so that the black hole either imploded or exploded?
With the argument I tried to outline, there was no black hole. The reason is, in short, the situation was not like where black holes are formed since then.
The big difference is that, (1), now, the matter-energy for a black hole is in some region of space in our universe where that region is surrounded by the rest of the universe, and (2), then, the matter-energy filled the entire universe that there was, even if it was only the size of a baseball. Then, that matter-energy filled the whole thing. For that whole thing to have created some small black holes, the thing would have had to have partitioned into separate chunks. But apparently what happened is that the space expanded explosively, really before anything could collapse. Or, maybe the expansion was so fast that quarks, as close together as in protons now, soon were being separated faster than the speed of light and, thus, had no choice but to generate more quarks and, thus, more matter. We're talking really explosively rapid expansion.
Or maybe the gravitational field of some matter-energy wanted to propagate at the speed of light, reach out, and connect with more matter-energy, but before that gravitational field had moved even 1 mm, space had expanded so much that the other matter-energy to be reached had already move to a few light years away. We're talking explosive, so fast that speed of light is so slow as to be nearly standing still and irrelevant. At least that is my intuitive understanding.
For al we know the percieved timescale of the big bang and the time since it is just timedialation, and that black hole might even exists in more than 3D.
So just like life in our galaxy may be a one in million chance, our universe it itself may be a one in a million chance.
I thought it wouldn't evolve deterministically? So what is he talking about here?
As far as science is aware, anyhow.