big bang

[Conceptual]

If one extrapolates the expension of the universe backwards it does seem to meet at the BB. There is a problem with BB in its existing guise. Data has appeared that inidicates that some galaxies formed less than 1 billions years after the BB. The existing continuum expansion model just cannot accommodate such rapid galaxy. formation. What would need to happen is a discontinuous expansion, where the BB breaks into chunks. Although this is a logical conclusion that fits the data, existing physics theory can not accommodate what is needed.

[Martin]

this is to stop the tangent in the parallel universe thread. the big bang was not the beginning of the universe. it says nothing of what banged, why it banged, how it banged, or where it came from. all it says is that at one point in universal history there was a rapid expansion from an extremely dense state. at this point, physics breaks down at the singularity, so right now we can't know much more than what i just said.

 

congratulations on getting into the nuclear submarine program.

 

there is a lot true in what you say----but there seems to be a divide between those who watch TV science programs and those who don't.

Here's my perspective as a reader of the (professional journal) print medium.

 

I quote the introduction of a paper by Ashtekar and Bojowald presented at the 10-14 October Quantum Gravity conference outside Berlin:

 

http://www.arxiv.org/abs/gr-qc/0509075

 

General relativity provides a subtle and powerful interplay between gravity and geometry, thereby opening numerous possibilities for novel phenomena. Among the most spectacular of the resulting conceptual advances are the predictions that the universe began with a big bang and massive stars can end their lives as black holes.

 

In both cases, one encounters singularities. Space-time of general relativity literally ends and classical physics comes to a halt.

 

However, general relativity is incomplete because it ignores quantum effects. It is widely believed that quantum gravity effects become significant in the high curvature regions that develop before singularities are formed. These are likely to significantly change the spacetime structure, making the predictions of general relativity unreliable. Hence, real physics need not stop at the big bang and black hole singularities. While the classical space-time does end there, quantum space-time may well extend beyond.

 

Classical physics comes to a halt IN THE CLASSICAL MODEL of cosmology provided by vintage 1915 General Relativity. That is because the classical Gen Rel model has a breakdown ("singularity").

 

Singularities (breakdowns) OCCUR IN THEORIES. No one has ever found a singularity in nature. No one has ever demonstrated that any sort of singularity must exist in nature. Singularities are not PHYSICAL---they occur in this or that theory, not in nature.

 

In the past it has been found that when theories had singularities (predicting haywire nonsensical stuff) people have been able to improve the model and get rid of the singularities. Now this has started happening in the case of classical Gen Rel.

 

from the standpoint those who watch PBS Nova programs it seems that "singularities" are real physical things (not just the temporary place where a man-made theory fails) because they see them on TV---our collective pre-rational imagination. judging from some of the posts on this thread "singularities" are something that exist in nature.

 

I think this may be part of the syndrome that it's not real unless its on TV and conversely if its on TV then ..... ....does that mean it's real?

 

Anyway I agree with Yourdadonapogostick when he says TIME GOES RIGHT ON BACK. Why not? No one has ever proved that it doesn't. the modern improved model (quantized) Gen Rel does NOT have the singularity, does not break down, and time goes right on back.

 

the job now, as with any improvement in any model, is to TEST it, which can be done by observing signature effects in the CMB (the microwave background) and related stuff in GRBs (gammaray bursts). It will take improved instruments----one is scheduled to go up in 2007----one is just beginning to report data.

 

This has nothing to do with strings or brane-worlds. It is just conventional mainstream cosmology such as people have been using for the past 50 years but gradually refining and improving----as when they measured the cosmological constant and adjusted for that----and in this case the step is to quantize it.

[ydoaPs]

thanks, but i'm not working on subs. i chose to work on carriers. it's less pay, but there are more people and i like not being completely submerged in case something goes wrong.

 

you say that singularities do not exist. i was under the impression that inside each black hole is a singularity. is that not the case?

[RyanJ]

you say that singularities do not exist. i was under the impression that inside each black hole is a singularity. is that not the case?

 

Yes singularities do exist within black holes for shure. Outside them is another matter. These are refered to as naked singularities and their existance is still debated so maybe thats whay was being refered too?

 

Cheers,

 

Ryan Jones

[[Tycho?]]

Yes singularities do exist within black holes for shure. Outside them is another matter. These are refered to as naked singularities and their existance is still debated so maybe thats whay was being refered too?

 

Cheers' date='

 

Ryan Jones[/quote']

 

I dont think its for sure actually. They are predicted by general relativity, but GR is generally not a theory for the very small. Once a valid theory for quantum gravity comes along we might find out that there is infact no singularity (a fairly popular position).

[JonM]

so was time the same 13.7 billion years ago, or always the same? or the same in other universes? Is time universal everywhere? Is it the same in black holes? Was time the same as it is now during the first miliseconds of the big bang?

[RyanJ]

so was time the same 13.7 billion years ago, or always the same? or the same in other universes? Is time universal everywhere? Is it the same in black holes? Was time the same as it is now during the first miliseconds of the big bang?

 

Good questions - I live them

I'll do my best to answer these.

 

If you think of it this way - space and time are one and the same according to GR and SR, therefor as long as space exists so too does time - did space exist at the point of the big bang I'm not sure but if it did then so too did time.

 

Time is relative, my time if a mixture of your time from yuor reference frame and everyone elses too... its also affected by gravity

 

Time in black holes - an interesting one. Because a black hole can be conidered a gole in space with spacetime being destroyed at the singularity you could say that time moves towards the singuarity and ends as you hit the singularity as itand space time and everything else are destroyed

 

Was time the same as it is now during the first miliseconds of the big bang? I have no idea - if space was there then time must have been also. All that mass in one space though can make things quite confusing

 

Maybe someone can answer these better than I?

 

Cheers,

 

Ryan Jones

[Martin]

thanks' date=' but i'm not working on subs. i chose to work on carriers. it's less pay, but there are more people and i like not being completely submerged in case something goes wrong.

 

you say that singularities do not exist. i was under the impression that inside each black hole is a singularity. is that not the case?[/quote']

 

It is not the case.

A singularity does not have a physical existence. It is a feature of a theoretical model.

 

whether you get a singularity or not, in some situation, depends on what model you use.

 

If you are modeling a BH and you use Gen Rel then it breaks down and gives meaningless answers at a certain place so YOU GET A SINGULARITY.

that just means you get a breakdown or glitch in the mathematical model.

 

if you are modeling a BH and you use any of several quantized Gen Rel models (lots of papers on this) then you do not get a singularity because they do not break down.

 

some authors who have written about this are Leonardo Modesto, Oliver Winkler, Viqar Husain, Parampreet Singh, Martin Bojowald, Abhay Ashtekar.

 

You can look their papers up on arxiv.org by authors name. Or if you have trouble and want help I can get the URL. they are available PDF for download.

 

most of one day at the annual quantum gravity conference (10-14 October) was devoted to this. it is fairly new work.

[Martin]

Yes singularities do exist within black holes for shure.

 

'']I dont think its for sure actually. They are predicted by general relativity, but GR is generally not a theory for the very small. Once a valid theory for quantum gravity comes along we might find out that there is infact no singularity (a fairly popular position).

 

RyanJ, AFAIK Tycho is right, in this case, and you are not. Perhaps you should hold off saying things like "singularities exist within black holes for sure", because it might confuse people. Thanks

[CanadaAotS]

http://stripe.colorado.edu/~yulsman/Instanton1.html

 

I love this idea of an "instanton" lol, plus the false vacuum bubble blowing up into the universe is cool too...

 

either way its better then having a 'singularity' since thats no good (apparently).

 

But where did all the matter and energy in the universe come from' date=' and what really put the BANG in the big bang? The theory actually does not say. In fact, contrary to common belief, the big bang does not explain the origin of the universe. It doesn't even explain a bang. Something had to happen before the big bang to get it going.

[/quote']

[ydoaPs]

It is not the case.

A singularity does not have a physical existence. It is a feature of a theoretical model.

 

whether you get a singularity or not' date=' in some situation, depends on what model you use.

 

If you are modeling a BH and you use Gen Rel then it breaks down and gives meaningless answers at a certain place so YOU GET A SINGULARITY.

that just means you get a breakdown or glitch in the mathematical model.

 

if you are modeling a BH and you use any of several quantized Gen Rel models (lots of papers on this) then you do not get a singularity because they do not break down.

 

some authors who have written about this are Leonardo Modesto, Oliver Winkler, Viqar Husain, Parampreet Singh, Martin Bojowald, Abhay Ashtekar.

 

You can look their papers up on arxiv.org by authors name. Or if you have trouble and want help I can get the URL. they are available PDF for download.

 

most of one day at the annual quantum gravity conference (10-14 October) was devoted to this. it is fairly new work.[/quote']thanx for clearing things up.

[Martin]

thanx for clearing things up.

 

I should thank you for not yelling at me when I give evidence of classical singularities having been removed. it's new work and people have not heard of it, and they have heard a lot about classical singularities, so naturally are reluctant to let go of the idea. this can get old for me.

 

it is exciting that you will be learning about power reactors.

 

start a thread sometime

 

I know something about reactors, or used to a couple decades ago.

it would be fun to hear stuff.

 

when do you start going to school (real school not just basic navy training whatever that is(?

[Martin]

duplicate, ugh

[Martin]

duplicate, moan!

[Martin]

duplicate, damn

[ydoaPs]

lol.....duplicates are a pain.

 

i go to basic on the 18th of July....not sure about A school though. i can't wait. high school just seems like it is getting in the way. it's odd watching all my classmates send out several applications to colleges and having no clue what they will do with their lives, when i know exactly(mostly) what my future holds.

[CanadaAotS]

When people think of the 'classical' singularity they probably think of (or at least I think of) spacetime looking like this:

 

 

Thats an image of the graph [math]z(y,x) = \frac{10}{x^2 + y^2}[/math].

 

Sorta reminds me of that halloween episode of the simpsons where homer found that portal to another dimension behind his bookcase and it turned him 3D lol. I think he dropped a bowling ball and it made a black hole (???) lol.

 

Anyways, most people don't think of singularities as some mathematical stupidity in a theory, more think of it as an actual thing.

[ydoaPs]

he kicked a cone

[CanadaAotS]

yah lol that was it

[RyanJ]

CanadaAotS - in what program did you do that diagram? It looks really good!

 

And the Homer Simpson falling down a black hole (Or was it a wormhole?) is great!

 

I actually think it was a wormhole though as anything that goes into a black hole is destroyed...

 

Cheers,

 

Ryan Jones

[Severian]

I think you guys have the wrong idea about the big bang. (I think you have been reading too much Hawkings.) The model of the big bang which you seem to be discussing is the one where there is a singularity at the 'big bang' itself. In this model, time is created along with space, so there is no 'before the big-bang'.

 

There are lots of other models too though, and in many of them there was time (and spce) before the big bang.

 

The problems is really that certain scientists, who are more interested in money than in truth, try to sell books explaining their opinions by misrepresenting them as fact. The fact is, we don't know what happened when we go too far back in time....

[Mart]

The fact is, we don't know what happened when we go too far back in time.... How far is too far?

[Severian]

The fact is, we don't know what happened when we go too far back in time.... How far is too far?

 

If you mesure time as in the conventional Big Bang model (with a singularity and a creation of time) then the Planck time is 10^-43s after the big bang. We don't know what happened at this point since we would need a theory of quantum gravity. We start to know what is going on after about 10^-9s. Earlier than that is just speculation.

 

Incidentally, the universe appear to be 14.2 billion years old or so.

[Mart]

Originally Posted by Severian

Incidentally, the universe appear to be 14.2 billion years old or so

Why do you use the word "appear"? To me "appears" is a somewhat weasily word in the context of the age of the universe. Are you hinting that the theory from which this result is derived is dodgy or that the theory is OK but the results are dodgy or both or something else? I hope this doesn't sound too picky and pedantic but I find certain words (perception, evolution, quality, appears) to be used so casually that they obscure meaning.

[Severian]

No - not really. I just said "appears" because cosmology has traditionally not been a very exact science. The 14.2 still has quite large errors on it (and quite a lot of inherent assumptions) but it is looking pretty firm. Of course, the need for dark energy in our current cosmological models may make some people uncomfortable.