Why Stephen Hawking says universe can create itself from nothing?

Chronos

Stephen Hawking is talking about a special case of 'nothing', which is a quantum state of the vacuum. A philosophical state of 'nothing' has no causal properties. The only choices I see are:
1] the universe supernaturally arose from a state of philosophical 'nothingness'
2] it arose from a quantum state [implying quantum states are somehow 'fundamental']
3] it has always existed, but, undergoes periodic phase changes [which ducks the question entirely]
Many scientists are attracted to choice #3, although it is no more satisfactory than 1 or 2.

Chalnoth

There are some difficulties with something arising out of nothing, when nothing doesn't experience time.

I really don't think you can describe a universe that is finite into the past in such terms. Rather, you'd have to have something similar to Hawking's no boundary proposal, where the "beginning" that we see is quite analogous to the north pole: the north pole is only special because of our definition of "north".

eltodesukane

"There are some difficulties with something arising out of nothing, when nothing doesn't experience time."
I agree with you.
Maybe the mere self-consistence of a mathematical structure makes it real.

jerryboy

The problem, whether you believe the universe was a nothing or a something is that the meaning of ...let's call it "something" with infinite energy and density is essentially meaningless because anything collapsed into singularity will take on the same characteristics. Take a loaf bread and crunch it into a singularity. You still get infinite temperature and density. These characteristics are artifacts of the mathematical equations but meaningless in the real world. This is because the singularity has no space. Without mass temperature and mass or density are meaningless. Krauss does have a whole book on this but his evidence is based on quantum vacuums which are definitely not nothings. If true then why haven't these expressed themselves in our universes by opening new universes here and there spontaneously, or even Black Holes, he presents no evidence that singularities are unstable. Harris is brilliant when it comes to Dark energy and matter, but when it comes to cosmology he's out of his league . The little gap between nothing and everything that ever was and every will be, cannot have characteristics since it is nothing.

Chalnoth

I think this is probably closer to the truth. Though sadly, we may never know.

CosmicEye

Watch Stephen Hawking's Grand Design. There was one where he talks about the relationship of time and the Big Bang, but also answers your question with logic that it came from literally nothing. Personally I lean towards the M-theory but it was something great to think about.

nazarbaz

Maybe what we call time (the flow of change from past to future states) is simply an equivalent to a quantum fluctuation of space: the degrees of freedom in which one single moment occur.
Ok, I'm speculating.

A_Seagull

Mathematics is actually about numbers. At least pure mathematics is. In order for mathematics to be applied to physics and other aspects of the real world some form of mapping is required that associates some part of mathematics with some aspect of the real world.

Strictly speaking deductive logic only applies to the labels that are words and not to the meanings of those words. The meanings of the words are too complex to be manipulated by simple logic. In this respect, mathematics and logic are distinct systems. Though by extending the axioms of each there may be overlap.

Chalnoth

No, it really isn't. Mathematics is about the study of self-consistent logical structures. Some of those include numbers, or can be represented in terms of numbers, but numbers are only a tiny part of the picture.

As the real world must be self-consistent, there is a mathematical structure which is the real world. We don't yet know what that structure is, but the purpose of physics is, essentially, to discover it.

jerryboy

Concentrated potential energy Prior to Planck time is an interesting hypothesis. But then where did that energy come from and what caused it to breach the Planck Boundary. Did this energy create itself from nothing and how did time create itself from pure energy. Are we then embarking on a new causal chain ending where? Pre-Planck energy is a something. Every something must have a cause. Only nothing can be not caused. The hypothesis only ivents a new causal layer leaving and requiring a new explanation and new cause. Problem not solved.

A_Seagull

I am not sure that it is particularly effective to claim that all self-consistent logical systems are a part of mathematics. What about Conway's game of life - is that to be considered a part of mathematics?

Even parts of mathematics are not entirely consistent with itself. For example modular arithmetic uses the same symbols as ordinary mathematics but its theorems are distinct. They require an identifier to show that they are not a part of ordinary mathematics e.g. 3+5=2 (mod 6).
If a system is self consistent within itself, what advantage is obtained by claiming that it is a part of the system of mathematics?

Regarding the nature of the physical universe, one does imagine that it is 'self consistent', but this may not necessarily be so. There could be an inherent inconsistency but one which is minor amount that it only destabilises universe at a rate which is slow enough as to be insignificant on a timescale of billions of years.
It could even be argued that the universe requires some form of instability or inconsistency, for otherwise it could never have been formed in the first place.
There is also the possibility that there is an inherent randomness in the universe that defies logical analysis as suggested by the results of Q M experiments.

There is also the problem of how it is possible to know whether the mathematical representation of the physical world is actually the one by which the universe actually operates. The mathematical representation may be highly accurate but no one seemed to be no definitive way of determining whether it is actually identical with the physical world.
For example, it has been noted that the universe works using modular arithmetic - modulo (10^~300). How would it be possible to distinguish the universe using ordinary mathematics (modulo infinity if you like) and one using modulus of a finite number?

Chalnoth

Yes. It's a cellular automaton.
http://en.wikipedia.org/wiki/Cellular_automaton
"A cellular automaton (pl. cellular automata, abbrev. CA) is a discrete model studied in computability theory, mathematics, physics, complexity science, theoretical biology and microstructure modeling."
(emphasis added)

This isn't an inconsistency in any real sense. An inconsistency is where within a particular mathematical structure, it is possible to prove a statement to be both true and false. This isn't possible as long as the rules of the mathematical structure are followed (because allowing such inconsistencies allows any statement in the structure to be simultaneously true and false).

Without consistency, nothing can make sense. For example, if I allow integer division by zero, I can prove that any number is equal to any other number, which completely destroys the ability of the theory to do anything at all.

That said, real structures used to describe our universe do have inconsistencies within them, but these are generally taken as evidence that the theory is incorrect in that regime. And, in fact, if we take the predictions of the theory seriously in those regimes where the theory becomes inconsistent, the theory loses all predictive power (because it can be used to predict anything). So what is done in practice is to cut out the part of the theory where the inconsistency arises (usually, but not always, this comes from some sort of division by zero).

Instability and inconsistency are very different things. There is no sense in which an inconsistency propagates: if the inconsistency isn't strictly hidden and blocked from any interactions with the rest of the mathematical structure, it makes the structure completely and utterly meaningless.

A_Seagull

And perhaps the theory is incorrect in every regime.

Chalnoth

At some degree of accuracy, sure, they're necessarily incorrect everywhere due to the existence of inconsistencies. However, they are excellent approximations in all situations we've yet measured.