[Colin2B]

U are rubbing me the wrong way
and victimizing me again!
.... I don't need this.

No one is victimising you.
New theories stay in new theories. Don’t advertise them here.
Yes, this section is for recognised current theories. As has been said before, we are far more lenient here than in other forums, but don’t abuse us, we don’t need that either.

[Halc]

One of the risks is that another round of expansion could start while we are still here, leading to the hypothetical possibility of a "Big Rip":
https://en.wikipedia.org/wiki/Big_Rip

The big rip usually refers to a FLRW solution where expansion becomes arbitrarily high at some finite time. Atoms would be torn apart only seconds after it happens to asteroids and such. This isn't 'another round of expansion'. Such a thing would occur at a location in space, which sort of grinds against the big bang model of the bang happening everywhere and not at any particular point in space.

I'd rather have the universe reset it self indefinitely at random than stay dead forever (heat death).

Under the eternalist interpretation of time, the universe is not in need of resetting like that. The interesting part just is, and cannot be in a state of no-longer-existing. This seems far more comforting that the horrid sentence of eternal life promised by the religions.

[Colin2B]

Have U heard of Quora?
There no one cares if U give a/the common sense answer.
That's probably why it's so popular.

It's also why I don't go to quora for answers if any other option is available.

I agree with halc, quora has the worst reputation of any science forum for quality answers.

[Colin2B]

Vell, I'll fix that, mein Liebchen.

you can’t fix quora, it’s broken. They need a New Theories section.

[evan_au]

I had to look it up: FLRW is a solution to Einstein's equations: https://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metric

As mentioned on another thread, some theorists think that the value of the cosmological constant that appears to govern the current expansion of the universe may be due to a quantum variable that can exist in several distinct states, with a rapid phase transition between these semi-stable states.

Cosmological inflation may have been such a phase transition. https://en.wikipedia.org/wiki/Inflation_(cosmology)

But we currently lack a bridge between general relativity and quantum theory that would permit us to determine if this is true.

[yor_on]

The big bang theory says nothing about the formulation of singularity or suggests a meaningful time outside of spacetime, which is what 'before the bang' is. So while a valid topic, it isn't a big bang topic. To suggest a time before the bang is to suggest that space is contained within time which contradicts relativity's spacetime where time and space are part of the same geometry with neither containing or supervening on the other, as you seem to be doing.

So... am I talking about an outdated/incorrect variation of the Big Bang theory then? I distinctly remember the description of a small, dense super hot region of space containing all of the universe's energy that expanded outward to fill empty space. As for the thing about time, that part I never understood since time is little more than the process of entropy gradually increasing overtime. Assuming the big bounce theory is correct, there's absolutely no reason whatsoever to think that there was nothing in the universe before the big bang began. If that theory turns out to be incorrect though and heat death will be the way the universe actually end, well... actually let's talk about that.



Yes it does. I don't think it was 'heat'. The cosmologists describe the conditions to their satisfaction since yes, such a simple description violates all kinds of rules. Keep in mind that the energy wasn't necessarily positive since there's an awful lot of negative energy present as well, and still is. Energy is conserved only in geometries that are static over time, and our universe isn't described by any static geometry (such as the Milne model). Just saying that the 2nd law doesn't hold in our universe. Carroll put out a paper showing this.

So... I'm right then? The big bang really did violate the second law of thermodynamics? Assuming that really is the case, that leaves me with so many other questions. Will the universe stay dead forever once maximum entropy has been achieved? Will time and space even exist after that? What even is space in the context of the big bang? How does all the rate of the universe's expansion and the amount of dark energy needed to drive it fit in with all of this?

Thx for the reply though, I really appreciate it :) 
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Had to quote you and I'm slightly tired so I won't bother with cutting it up :)

I don't know of any 'negative energy' anywhere, unless we're speaking metaphorically. Usually it's referred to as 'gravity' but gravity is positive as far as I know. And the idea of something very hot and constricted creating a 'explosion' (ftl) of a universe makes little sense to me if you consider the way we expect everything to be and look the same, wherever you are and at no matter what time. Those are fundamentals of physics, it's from there it builds. Frames of reference and how they treat a 'same observation' is a different thing.

Isotropic and homogeneous, our universe, and that includes laws, principles and properties.   http://curious.astro.cornell.edu/about-us/101-the-universe/cosmology-and-the-big-bang/general-questions/574-what-do-homogeneity-and-isotropy-mean-intermediate

I don't think we can assume that thermodynamics existed before a Big Bang. The laws, principles and properties we know of belongs inside our universe. What existed without that universe interacting is unknown. Then there is another thing, if a Big Bang has no defined origin, or turned around, is centered at you wherever you are and at whatever time, as well as on me and everyone else. Then it becomes quite confusing thinking of it as a 'hot' Big Bang, you can look up cold Big Bangs if you're curios, I know I was :)


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What I think is worth noticing there is that locally defined everything makes sense, the problem comes when introducing frames of reference. Then the concept of 'time' becomes fuzzy, but locally defined it doesn't matter where you are, at what mass, or how fast you 'move' relative some reference frame. Your lifespan, as measured by your wristwatch, will be the same, and so will those laws, principles and properties. We build the physics we know from local observations, when our observations (experiments) agree we call them repeatable, and so 'globally valid'.

Can't help myself here, do you notice how well it fits with what I described first :)
The universe is strange.

The correct definition of gravity should be that it acts as well as getting acted upon. There are no negatives involved in that, that I can see, and 'relativistically speaking' it's a equivalence to a acceleration, meaning that Earth is at a constant uniform one gravity of acceleration, at all times. Loosely speaking.

[yor_on]

Let me evolve the way I described it a little. Astronomy and main stream theories builds on the concept of of the universe being the same, locally described, wherever you are and at whatever time. That is to me a equivalent to the way main stream physics expect laws, principles and properties to be the same, wherever you are and at whatever time. It's one of the big questions if it/they always have been the same, and as far as I'm concerned I don't expect any deviations there. 'c' f,ex will be 'c' and a limiter of 'useful information', no matter at what time period you're looking at.

What it astronomically (as welll as physically) states is that no matter where you 'teleport' yourself, this universe should look and behave a same way (astronomically defined from a huge scale). And the same is expected by our physics, laws, properties and principles. From it comes a question, or several questions. If now the universe will look the same as before, as I now teleport to its 'fringe', information wise expressing itself in form of light coming from some ~13.8 billion light years ago, presenting the same once I arrived, in where you still find you surrounded by a 'bubble' of light, 13.8 billion light years in all directions, how can the universe be anything but 'infinite'?

And how can there be a 'origin' to a 'Big Bang'? You can add more 'dimensions' to presume something hidden from our observations, but it also depends on what you mean by those 'dimensions'. Normally defined they becomes coordinate systems, like length, width and height. Einstein added 'time' to them, so now we find us needing length, width, height and time. Or define it as a holograph in where some of those 'dimensions' becomes a construct from a hidden reality containing fewer dimensions, similar to the way a holograph works.

If you accept main stream definitions there is no origin to a Big Bang inside the coordinate systems, or 'dimensions' we use. And 'time' is fuzzy. But that description, as well as the astronomical, builds on a concept of a 'global definition'. the one I mentioned above.



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If you want to consider it as a holographic rendering then you add to the questions, as the 'reality' we define works perfectly well with the coordinate system we use. So what part of them should I consider 'unreal'?

If you do the opposite and add 'dimensions' then? Actually it reminds me most of 'frames of reference', in some way becoming mirrors of each other.

So personally I think we need some other way to define it, those coordinate systems. If we want it to work, and locality works, makes a awful lot of sense, but it doesn't explain this global concept, the one in where it interacts and becomes a universe..

Heh, thinking of it, I would like to see a mathematician defining a 'origin' to any 'infinity'. You could start at one of course, or null? Can a infinity have a origin?
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If we use the concept of clocks you have two choices. Either all local clocks, used to define other clocks from lie, or they are true. That's where you can use the idea of a 'predefined local' life span to test it. Defined that way they don't lie, again strictly locally defined. Defined the opposite way all local measurements become unreliable as you don't have a trustworthy clock to define them from, much in the same way as we then can assume all other measurements of our coordinate system to be unreliable. Everything becomes relative and we will never be sure of a consensus, even when defining something as a repeatable experiment.

That one you can test by imagining three observers in relative motion measuring each other clocks durations, assuming them at different relativistic speeds versus some agreed on origin (f.ex earth). They will all give each other different time dilations. Actually I think that 'repeatable experiment' is another proof for this local definition, which is what those ships should be able to prove, doing those local repeatable experiments finding a consensus.

Without this definition you will have a very hard time explaining what a 'repeatable experiment' involving clocks builds from. And I expect that this must hold for GR too, it will definitely hold for SR. If it is correct we have 'grains' of time, locally defined. Your lifespan one example of this idea, repeatable experiments another.