Hawking On The Edge Of The Universe

[TimBowe]

If Hawking's model is correct then the universe could be regarded as a causally closed system, uncreatable and indestrucible.

Hawking: It obviously matters because if there is an edge, somebody has to decide what should happen at the edge. You would really have to invoke God.
Why does that follow?
Hawking: If you like, it would be a tautology. You could define God as the edge of the universe, as the agent who was responsible for setting all this in motion.
You are invoking God because we need an explanatory principle for the edge.
Hawking: Yes, if you want a complete theory, then we would have to know what happens at the edge. Otherwise, we cannot solve the equations.
In the sense that you're using God, it's rather like a principle that's synonymous with the laws of the universe. It doesn 't imply a moral being.
Hawking: There would not be a connection with morality.
You're using it as a logical and causal principle.
Hawking: Yes.
You said if there is an edge, then we 'd have to invoke God. Do you think there is evidence for an edge?
Hawking: At the moment there's not much evidence either way. It seems that we can explain the present state of the universe on the assumption that there wasn't any edge.
You said earlier that, in so far as the possibility of an edge of the universe is concerned, it could go either way, and you correlated the edge with a God or some sort God-like principle.
Hawking: It's very difficult to prove that there isn't any edge, but if we could show that we can explain everything in the universe on the hypothesis that there is no edge. I think that would be a much more natural and economical theory.

 

[TimBowe]

Hawking's model says space-time has no boundary and no edge, that it is boundless, unbounded, and unlimited. There is no edge to spacetime, the universe is completely self-contained and has no beginning.

 

[TimBowe]

In Hawking's model the universe is finite, but without an outside. There is nothing outside it. More precisely, there is no outside.

According to Hawking's proposal the past of the universe is finite (as is in the Big Bang model) but, unlike the past of the Big Bang, it is unbounded.

 

[TimBowe]

In Hawking's edgeless universe all space-time would be finite and edge-less.

 

[TimBowe]

?

 

[bapowell]

What exactly is your question, Tim?

 

[emc2cracker]

Personaly I love Hawking's ideas, he has a very open and creative mind. There is a huge problem with a universe that sprang from nothing and has boundaries.. that problem to me (even if there is some supreme intelligence that sets things in motion) is simply stuff doesn't come from nothing, I believe eventually we will figure out the universe with or without a big bang is a cycle that came from something be it energy or matter. I don't subscribe to the idea that what we see today was just always here and has no transitional states... so far as we have seen EVERYTHING has transitional states so why not the entire universe. I don't like the idea of invoking other dimensions and other untestable ideas either, I think there should be an explanation for this universe and inside this universe.. at least I hope lol. It seems the mind of Hawking has been turning on that notion as well and that comforts me a little, most everyone seems to be persuing the same old questions instead of just asking new questions.

 

[Chronos]

Even in an oscillating universe, you must eventually concede the 'something from nothing' conjecture is difficult to refute. You need not concede the 'god' concept, but, it is a tempting explanation.

 

[TimBowe]

The universe didn't come from nothing, in Hawking's model the universe was never created, it always existed.

In Hawking's scenario, the universe doesn't have to be created from nothing. It's just there. It is a geometry of space and time. When the geometry changes- that is, when imaginary time becomes real time the universe begins. The change from nothing to something is literally a change in geometry.

"I wouldn't describe it as a universe being created from nothing, instead the universe just exists as closed Euclidean geometry. It doesn't have time so it doesn't have a beginning or end. The time we experience is something we construct."

Stephen Hawking

 

[emc2cracker]

Yes Chronos today with the universe as we see it and the models we are using something from nothing seems apparent and self evident. However as far as refuting it, until we create particles from nothing we can't exactly say for certain anyway.

But as the old saying goes, sometimes there is more than one right answer. I think that is our current problem in cosmology.

Even in the big bang the universe doesn't come from nothing.. it comes from an infinetly small and dense point that is very hot. That doesn't happen on its own something sets that in motion or else big bangs would happen randomly would they not? I apologize if I"m missing something here, I'm working with the best of my knowledge and materials I have lol (maybe not alot!)

 

[TimBowe]

Hawking's variation on the traditional model

In attempting to surmount the singularity problem Hawking has used an ingenious mathematical technique. By changing the time measure in Einstein's field equations to imaginary time he has placed time on a mathematically equivalent basis to space.

Imaginary numbers are a perfectly respectable tool of mathematical manipulation, the term 'imaginary' having nothing to do with any notion of illusion or maya, etc. By thus treating time as if it were imaginary space this provides a model where the Universe commences as a point, or an infinitely small circle at the bang at time zero.

For, as at the north pole of the Earth there is no 'edge' to the globe and all directions are south, there being no direction 'north', so in Hawking's model there is no 'edge' to time since all time directions after the bang at zero time are the future, there being no direction of time corresponding to 'the past'. Thus crossing the moment of zero time leads to the future just as crossing the point of the north pole of the Earth always leads south.

 

[bapowell]

Even in the big bang the universe doesn't come from nothing.. it comes from an infinetly small and dense point that is very hot.

No. The standard big bang model does not address the initial singularity. The initial singularity (all singularities really) are considered to be points at which the physical theory is breaking down and that a more complete theory of UV gravity takes over. The standard big bang theory is the model of the universe as it expands from an early, hot, dense phase -- it says nothing about the initial moment.

 

[Chronos]

It remains a fascinating mystery. I'm not convinced we will ever find a definitive answer.

 

[emc2cracker]

Singularities are addictive subjects... places where we can have pink elephants or fly.. where logic goes right out the window and the infinite is just sitting there waiting for the next genius to fix it.

Its depressing knowing if we ever do find a solution its likely to be far into the future if at all...

 

[TimBowe]

In the very early universe space-time existed in a more primitive state where time itself was simply another direction in space.

According to the ideas initiated by J. Hartle and S. Hawking, "the universe, at those extreme densities where its quantum attributes become overwhelming, behaves like a four dimensional ball".

 

[jackmell]

Personally I find comfort with "singularities". Throughout Nature, there exists phenomena that sometimes do not change smoothly but rather reach a point and suddenly and often abruptly change state. I've grown confident these are reflections of our Universe in general so it's easy for me to extrapolate to the farthest reaches of space and deepest recess of matter and conclude our difficulty comprehending such things as "something from nothing", "the smallest small", "a beginning of time", the "origin of the Universe" and the "edge of the Universe" is because we fail to recognize the presence of "critical points" in phenomena which often cause qualitative change in the dynamics of the phenomena rendering useless the models we used to describe phenomena before the critical point.

If "nothing" is qualitatively different than the something we now observe in the Universe then I find no difficulty at all believing our Universe came from "nothing". So too I believe with an "edge" of the Universe. It's not as simple as "it just stops" just like when we believed ships sailing off into the sea would suddenly fall off the earth. It's going to be something different, qualitatively, than what we think about the world so an "edge" to the Universe is really in my opinion not applicable. The same thing goes for the pre-existence: what reached a critical point and created our Universe I am confident we will one day grow to understand and feel that understanding will require quite a different description of existence than what we currently use today.

The reason we reach paradoxes about Nature, I believe, is because we attempt to describe it beyond such "singular" points using descriptions which are not applicable precisely because of the singular point.

 

[emc2cracker]

I like singularities but for a different reason, for me they stand for the quest of knowledge itself. They are beacons begging for an explanation. And I think we fail to recognize these "critical points" because we have never seen one.. we have evidence to support their existence but that answer still eludes us. Thus we have a quest, to quote the great Einstein in his correspondence with John Moffat all those years ago, "What we have is a box, we must decide whether to open that box" or something to that affect.

Einstein himself searched for a more perfect universe as we should.

 

[jackmell]

And I think we fail to recognize these "critical points" because we have never seen one..

Maybe you're referring to the Big Bang but in ordinary life, we see critical points all around us. The point at which water freezes is a critical point and some descriptions of water reach a "singular point" and cannot be applied to the solid ice. For example, the slope reaches an infinite value and it's past that point that we use some different descriptions to describe it's solid behavior.

In the text, "Perspectives of Non-Linear Dynamics", the author asks,

"what happens to a fly, a corporation stock, a star, or a civilization when respectively a venus flytrap closes, there is a stock market crash, it becomes supernova, or a nuclear war breaks out?"

Singular points are reached in these cases (I believe) and the descriptions for the fly, markets, civilizations, and stars cannot (in some ways) be used to adequately describe the dynamics of the phenomena past these singular points.

I bet that's the way it is with the Universe as a whole. Some qualitative extension of our current understanding will be required to further our understanding of it in the same way the qualitatively different "round earth" was used to answer the question of what happens if we keep walking in a straight line.

Just my opinion. :)

 

[emc2cracker]

I am talking strictly cosmology, I got the impression you were calling singularities in cosmology critical points.

In short I believe if there is a supreme intelligence then he is a scientist, as such everything we see should be explainable by physics. I am excited to be alive and studying cosmology, I have this crazy dream that maybe years down the road I can contribute, and if I cannot master the math then I'll leave it up to my children whom I am trying to brainwash into becoming cosmologists lol.

I respect your outlook though and I am by no means saying you are wrong, the plain truth is none of us here can say for sure... it may be that infinities are a crucial part of this universe being here and have no explanation.. but I like to think we can figure it out in due time.

 

[TimBowe]

No physicist holds that the singularity actually exists it's just an ideal mathematical limit to a series in a sense of calculus.

 

[TimBowe]

In Hawking's model time becomes another dimension of space, it is spatialized.

We might decide that there wasn't any singularity. The point is that the raw material doesn't really have to come from anywhere. When you have strong gravitational fields, they can create matter. It may be that there aren't really any quantities which are constant in time in the universe. The quantity of matter is not constant, because matter can be created or destroyed. But we might say that the energy of the universe would be constant, because when you create matter, you need to use energy. And in a sense the energy of the universe is constant; it is a constant whose value is zero. The positive energy of the matter is exactly balanced by the negative energy of the gravitational field. So the universe can start off with zero energy and still create matter. Obviously, the universe starts off at a certain time. Now you can ask: what sets the universe off. There doesn't really have to be any beginning to the universe. It might be that space and time together are like the surface of the earth, but with two more dimensions, with degrees of latitude playing the role of time.

Stephen Hawking