Original location of the Big Bang

[Jack Bauer]

Would it be possible by comparison of expansion rates and directions at various points to back-extrapolate the location of the original Big Bang? Certainly in a local part of the universe, everything is expanding away from everything else with rates and directions as if the whole expansion were homogenous but if the universe arose at one point, I would think analysis of vastly separated points would show subtle differences that would point to the location of that one point. Just as with sufficient data points within an expanding sponge that had been squeezed into a tiny wad we should be able to deduce the center of compression of the sponge before it was allowed to expand -- or is this too unknowable?

 

[marcus]

Would it be possible by comparison of expansion rates and directions at various points to back-extrapolate the location of the original Big Bang?

Not in any meaningful way.

any point in today's space that you pick
has an equal claim with all other points to being the "location of the original Bang"

the Bang event was not an explosion of stuff "in" some pre-existing space, so it cannot be traced back to a point in space.

typically astronomers do not picture the Bang event as an explosion IN space but as the beginning of the observed expansion OF space.
(they do not suppose there was some surrounding other kind of space in which our space began expanding---perhaps there is or was some surrounding space, possibly higher dimensional, but I know of no way to ascertain this)

there is a Scientific American article available online which deals with several misconceptions people often have about the expansion of space and its beginning. Would you like the URL so you can read it?

Anyway, the answer to your question is that in the usual model of cosmology that astronomers have, ALL POINTS ARE EQUALLY the location of the beginning of expansion.

(or else you could say that there is no "location" of the onset of expansion---the idea is not well-defined because there are no relevant coordinates)

the Sci Am article is by Charles Lineweaver. You might like it. ask if you want the URL.

 

[Jack Bauer]

Thanks, yes I would like the URL for that article, if you get a chance.

 

[marcus]

Thanks, yes I would like the URL for that article, if you get a chance.

https://www.physicsforums.com/showthread.php?p=482299#post482299

should be several active links in that post,
please tell me if you have any trouble.
the article was by Lineweaver and Davis

 

[marcus]

to facilitate, I just copied that whole post


http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

Popular written feature article "Misconceptions about BigBang"
Here are some sample "sidebars" of the article. Each has one or more visual diagrams with a wrong answer discussed and a right answer explained.


http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p39.gif
What kind of explosion was the big bang?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p40.gif
Can galaxies recede faster than light?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p42.gif
Can we see galaxies receding faster than light?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p43.gif
Why is there a cosmic redshift?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p44.gif
How large is the observable universe?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p45.gif
Do objects inside the universe expand, too?

 

[Jack Bauer]

Marcus, thanks for the links. I just read the whole article -- really helpful.

Some things occurred to me. If some objects are "receding" from us faster than the speed of light because of expansion of space, could this be a way of traveling faster than light? If we could somehow cause such expansion (by using whatever force or process is causing the universe to expand) locally, along a particular path, could we "expand" a spaceship over to a certain part of the universe? Or conversely could we "pull in" a particular part of the universe by reversing expansion along a particular path? An analogy would be a frog bringing an insect back on its tongue :)

Also although I understand the current BB theory posits that expansion was "from everywhere", not from a particular point, why? Has the alternative of expansion from a particular point been disproven? It seems to me there is a lot of variation in the velocities of expansion when you look around -- do these really not point to a particular part of the universe as the "oldest"/least expanded?

 

[marcus]

Some things occurred to me. If some objects are "receding" from us faster than the speed of light because of expansion of space, could this be a way of traveling faster than light?

cute idea
but personally, I think not:
"travelling" involves the idea of "getting somewhere"
and recession speed doesn't get you closer to any destination


imagine someone in a galaxy X that is 27 billion LY from us.
We see galaxy X receding at speed = 2c

he sees us receding from HIM at speed 2c, but he doesn't see us catching up with light, or getting closer to anything

we see him receding from US at speed 2c, but we don't see him catching up with anything, or approaching anything. All the space around him in his local neighborhood is also receding from us at about the same 2c speed.

recession speed doesn't "do any good" to anybody in a transportation locomotion sense-----as animals we have this instinctive urge to go somewhere so it's natural to ask what you can do with the expansion of space: can you save on gasoline bills, hitch a ride, etc.?

Most likely not.

But it does a lot of good for us in other ways. If space were not expanding we would be getting cooked by the accumulated light. If it hadnt expanded 1000-fold since the time the CMB light was released we would be like standing in front of a 3000 Kelvin heat lamp turning crisp and then getting vaporized
the expansion is nature's way of COOLING the light that is coming to us from all directions. So it is a nice cold 3 Kelvin. think of it as air conditioning for the universe

 

[BoTemp]

Remember warp drive, on star trek? It's not theoretically impossible. "Gravity" by Hartle has a box about it in chapter 20. Basically, you need to be able to shrink space in a region surrounding you. It's impossible to travel faster than light locally, but the distance you're covering is shorter so you can cover a distance in a shorter amount of time than a light ray would.

This would require negative energy to create, which may exist, but has never been observed. So don't hold your breath.

 

[EL]

http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

Marcus, this is a really nice text! It should be a sticky or something like that.

 

[russ_watters]

Remember warp drive, on star trek? It's not theoretically impossible. "Gravity" by Hartle has a box about it in chapter 20. Basically, you need to be able to shrink space in a region surrounding you. It's impossible to travel faster than light locally, but the distance you're covering is shorter so you can cover a distance in a shorter amount of time than a light ray would.

Unfortunately, though it would work, that would only be useful for tunnels, not for spaceships, because the field that "warps" local space to allow shorter travel distances is itself constrained by Relativity to propagate at C. If, for example, you were going to travel to Alpha Centuari, you'd need to let the field propagate for 4.5 years before you could enter the tunnel and travel there. There is a benefit, though - you'd save on fuel.

 

[XanPaul]

So then could it be, or has it been, said that everywhere in the obsevable universe is the sight of the Big Bang? Because of expansion, the Big Bang not only occurred but is still occurring in some way? Like being inside a giant "explosion" as it's happening? The point it occurred at just expanded to create the empty space between all the matter that was there from the start?

 

[marcus]

... Like being inside a giant "explosion" as it's happening? The point it occurred at just expanded to create the empty space between all the matter that was there from the start?

That's pretty decent as an initial description. You might enjoy these two articles
Lineweaver SciAm article "Misconceptions about the Big Bang"
http://www.astro.princeton.edu/~aes/AST105/Readings/misconceptionsBigBang.pdf

And "A Tale of Two Big Bangs" at Einstein Online (a research institute's outreach website)
http://www.einstein-online.info/en/spotlights/cosmology/index.html

These articles will help your refine your picture quite a bit. They are both aimed at eliminating common misunderstandings about the standard cosmo model.

Be careful not to rely too much on the "explosion" picture. The standard big bang model is not like an actual explosion with stuff flying out into empty space---from some central location. I think from what you say you understand this though---there is no surrounding empty space, distances simply increase.

In a figurative sense, the pattern of increasing distance as you say "creates the empty space" between galaxies etc. But space is not a substance that needs to be created, at least as far as the general relativistic models in cosmology are concerned. The main thing is simply that the distances increase and if you figuratively say that creates space OK.

 

[Judycrayton]

Marcus, thank you so much for all this information. My mind isn't really grasping it but at least I know what it is I'm not grasping :) That is much better than before.

 

[mrspeedybob]

My mind isn't really grasping it but at least I know what it is I'm not grasping :) That is much better than before.

That's going to be an immortal quote.

 

[Judycrayton]

Why thank you ms speedybob. What a nice welcome :)

 

[Kevin_Axion]

I'm not sure if you're being sarcastic but his reasoning isn't different from many other scientists, the current state of physics has no grasp on these questions although we are approaching them through String Theory and LQG.

 

[marcus]

Marcus, thank you so much for all this information. My mind isn't really grasping it but at least I know what it is I'm not grasping :) That is much better than before.

I'm glad you brought back this thread, Judy. I still think the factual content is up to date and useful. I know what you mean about getting a handle on what puzzles you. It can help just to be able to narrow down and say more definitely what it is you find hard to understand.

The Lineweaver SciAm link in the 2009 post needs to be replaced. The old one at princeton.edu doesn't work anymore but there's a new one:
http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf
When you go there, the file has one blank page at the beginning, so just scroll down. Don't think it isn't working because you just see a blank page.

I'm not sure if you're being sarcastic but his reasoning isn't different from many other scientists, the current state of physics has no grasp on these questions although we are approaching them through String Theory and LQG.

Kevin, thanks for the supportive comment. I tend to look at it from the "half full" perspective---personal perspectives differ: I tend to think that physicists have made significant progress in grasping "these questions". Depends on what you mean, but I think Judy is puzzling over some things that came to light in 1915-1935.

What is space and how can it expand without some other kind of space for it to expand into?

Answer (Einstein, Friedmann, Hubble...1915-1935): In the most primitive sense, space is not a thing or substance but rather space is just the distances between things. All expanding means is that distances between things increase---by a certain percentage every million years, the percentage can change over longer periods of time. And that is only distances between things far enough separated so that gravity doesn't bind them to each other and interfere with their separation growing.

The current rate is about 1/140 of one percent per million years. It's not something you'd notice except with distances that are already very very large, because it is such a small percentage. And the number 1/140 is very very slowly diminishing

So space is not a thing, it doesn't need to have some other kind of space to live in, it is simply the catalogue of distances between things, and it is "expanding" in the sense that there is this regular pattern of percentage increase---which is actually governed, we think, by a certain simple equation first written down by Alex Friedmann around 1923-1925

And because it is simply the distances between things, it doesn't need to have a boundary. It is too simple an idea to need a boundary or some other kind of "space" to live in. It can expand in a pure simple way without any of the usual accessories.

Judy, admittedly that still leaves huge awesome questions to wonder about!
But it is already a great achievement for people to be proud of. Kevin talked about grasp. Alex Friedmann gave us a terrific grasp of this process by discovering an equation that seems to spell out how that percentage rate changes over time! And there was a bonus, in that his equation was derived from, and explained by, Einstein's 1915 equation (which is something we can test in Earth orbit, and within the confines of the solar system, an equation describing the relation of gravity and geometry.) So that put Friedmann's cosmology formula, which on very large scales describes expansion, on an empirical footing---connected it to something testable.

So on the one hand it's great, and there is a real grasp---and on the other hand there are still huge mysteries.

Yes the 1925 Friedmann equation is very good, and agrees with tons of evidence, millions of observations, but if you follow it back and back and back in time eventually it stops making sense---it says infinite density. A singularity is, by definition, something unphysical, a failure of theory. It is the breakdown of a model that has been pushed too far.

So, with this wonderful grasp that Einstein Friedmann Hubble and others gave us, we also get this problem of what, in reality, replaces the bang singularity?
My "half full" view is I am very glad we have come as far as we have and I am not worried by this problem. I see progress, I see it being addressed. The research area that deals with this is called "quantum cosmology". It is cosmology around the time of big bang, when the concentration of energy was so high that quantum effects make a difference (and may even reverse the effect of gravity and make it repel instead of attract.)

The first textbooks and popularizations dealing with what is currently mainstream quantum cosmology (QC) are beginning to appear. But what is mostly available is stuff laypersons will NOT want to read. You might look to see who the main authors are though.
Here are the technical research papers keyword "quantum cosmology" date > 2005 (i.e. last five years) ranked by number of citations (most cited papers listed first).
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+cosmology+and+date%3E2005&FORMAT=WWW&SEQUENCE=citecount%28d%29

Looking at the authors of the first 20 or so papers (the 20 most cited) will give an idea who the main authors are and what names to look for when QC books begin to appear.

 

[ViewsofMars]

That's pretty decent as an initial description. You might enjoy these two articles
Lineweaver SciAm article "Misconceptions about the Big Bang"
http://www.astro.princeton.edu/~aes/AST105/Readings/misconceptionsBigBang.pdf

Hi marcus. The pdf isn't working for me. Test it out. Please. Thanks.

Be careful not to rely too much on the "explosion" picture.

Yep, you are correct. From NASA, NASA Official: Dr. Gary F. Hinshaw, Page Updated: Monday, 05-24-2010

Please keep in mind the following important points to avoid misconceptions about the Big Bang and expansion:

- The Big Bang did not occur at a single point in space as an "explosion." It is better thought of as the simultaneous appearance of space everywhere in the universe. That region of space that is within our present horizon was indeed no bigger than a point in the past. Nevertheless, if all of space both inside and outside our horizon is infinite now, it was born infinite. If it is closed and finite, then it was born with zero volume and grew from that. In neither case is there a "center of expansion" - a point from which the universe is expanding away from. In the ball analogy, the radius of the ball grows as the universe expands, but all points on the surface of the ball (the universe) recede from each other in an identical fashion. The interior of the ball should not be regarded as part of the universe in this analogy.

- By definition, the universe encompasses all of space and time as we know it, so it is beyond the realm of the Big Bang model to postulate what the universe is expanding into. In either the open or closed universe, the only "edge" to space-time occurs at the Big Bang (and perhaps its counterpart the Big Crunch), so it is not logically necessary (or sensible) to consider this question.

- It is beyond the realm of the Big Bang Model to say what gave rise to the Big Bang. There are a number of speculative theories about this topic, but none of them make realistically testable predictions as of yet.
http://map.gsfc.nasa.gov/universe/bb_concepts.html

 

[alt]

Hi marcus. The pdf isn't working for me. Test it out. Please. Thanks.




Yep, you are correct. From NASA, NASA Official: Dr. Gary F. Hinshaw, Page Updated: Monday, 05-24-2010

From the NASA quote in the aboe post;

That region of space that is within our present horizon was indeed no bigger than a point in the past.

Point; A geometric element that has position but no extension (Wordweb)

In which case the above NASA statement is very difficult to comprehend.

 

[Judycrayton]

I made a quick reply yesterday and I see it disappeared. I'll use the 'reply to thread today.

"In neither case is there a "center of expansion" - a point from which
the universe is expanding away from."

This does surprise me. I actually remember (I'm 71) standing at my front door in my early 20's (mid 60's) reading the KC Star one morning and being very excited because the article said they had discovered the exact spot in space where the big bang happened. For some reason that spurred me on to get books to study. Now I wonder what it really said :) And I'm still reading with that idea in mind. I've probably read things into the writings that weren't really there.

Another thing that enlightened me was your definition of a singularity. I've always thought of one as the center of a black hole without the black hole. The naked singularity. When that term was used to have anything to do with 'the beginning' it never made sense. It is the result of gobbling up matter. But from what you say, am I correct to think of a singularity as any thing that operates outside our known law of physics?

I have no trouble thinking of space, itself, as nothing ... although it messes with my understanding of Einstein's theory of gravitation which I cold never grasp. I'm thinking of the pictures I saw that show planets sinking into some type of particle type netting. The bigger ones sinking deeper than the smaller. It was that deviation in space that was calling us to fall into bodies of matter. But how could that happen in all 360*? I would think the existence of gravitons would rule that out.

If there was not an explosion involved in the appearance of matter, where did the massive energy come from.

 

[Fredrik]

Hi marcus. The pdf isn't working for me. Test it out. Please. Thanks.

He included the new link in post #17 (the one before yours). It's also in his signature.

 

[Kevin_Axion]

Marcus, what is loop quantum cosmologies perspective on gauge/gravity duality and holography? These appear to be very important components in describing quantum gravity, at least in the context of superstring-theory and string cosmology/string gas cosmology.

 

[marcus]

Marcus, what is loop quantum cosmologies perspective on gauge/gravity duality and holography? ...

It's off topic in this thread but you might look here:
https://www.physicsforums.com/showthread.php?t=179140

It's 2007 and so not the latest---just shows where the field was 3 years ago.

More recently, one of the top LQG researchers, Laurent Freidel, gave a PROOF of the AdS/CFT correspondence in the special case 2d CFT and 3d bulk. He was able to arrive at a formula which would reconstruct the bulk explicitly from information given on the boundary. That kind of thing is interesting because AdS/CFT is still a conjecture. One does not know how to solve the general problem of reconstructing bulk from boundary information, or even if the mapping is unique.
http://arxiv.org/abs/0804.0632

The holography like LQG result about black holes goes back, IIRC, to around 1996, but that was only a beginning. LQG made contact with holography a long time ago and every now and then there is a new paper and some more progress in that department.

You might find some stuff in Smolin's January 2010 paper about the LQG entropic force---since it deals with horizon entropy.
http://arxiv.org/abs/1001.3668
Let us know if you find anything interesting!

 

[Kevin_Axion]

Yea, sorry about that, I just didn't feel like private messaging or making a new thread. Thanks though.

 

[raynicolle]

It seems to me that saying the observable universe is expanding because we can observe it traveling away from us...but then saying the observable universe did not originate in anyone point in observable space is very confusing. I think physics seems to attempt to describe the observable universe by using descriptions of mathematical universes...but mathmatical universes are not real. Physics can't have it both ways. If there is direction to the expansion of the observable universe then you should be able to determine the origin in observable space. The quandry is that the observable universe seems to originate at our galaxy. That points to erronious assumptions in measurment...not to Earth being special.

 

[Cosmo Novice]

It seems to me that saying the observable universe is expanding because we can observe it traveling away from us...but then saying the observable universe did not originate in anyone point in observable space is very confusing. I think physics seems to attempt to describe the observable universe by using descriptions of mathematical universes...but mathmatical universes are not real. Physics can't have it both ways. If there is direction to the expansion of the observable universe then you should be able to determine the origin in observable space. The quandry is that the observable universe seems to originate at our galaxy. That points to erronious assumptions in measurment...not to Earth being special.

I think the problem you are having grasping the concept is this: There was no "point" in space prior to expansion for the BB to begin in. Somebody on this forum stated that: "geometrically the big bang began everywhere at once" which makes complete sense as when t>0 (and after Plancke time) the "size of the universe" may be limited but this is not to say it is finite. It is not possible for the BB to have occurred "anywhere" in space as prior to the BB there was no space. U=the totality of everything, U began at BB, therefore is is not possible for the totality of everything to begin somewhere (as there is no somewhwere prior to BB)

This is stipulated by U being isotropic and homogenous.

I am a novice as my name indicates so anything I have stated is not necessarily a fact but what I believe is current cosmo consensus.

Thanks

 

[raynicolle]

I think I grasp the concept but it is not a concept that seems to apply to the "observable universe". It applies to a mathematical universe...an imaginary universe. In the "observable universe" things are expanding at a measurable rate and should be backwards measurable to a specific point. My point was that physics seems to easily jump back and forth between the the "observable (real) universe" and various mathematically conceived universes and, in doing so, creates impossibilities. I realize that the mathematical "universes" are necessary to attempt predictability but physics seems to blur the difference between reality and theory in order to give pat answers. Because of this, physics seems to be chasing it's own tail.

 

[Cosmo Novice]

I think I grasp the concept but it is not a concept that seems to apply to the "observable universe". It applies to a mathematical universe...an imaginary universe. In the "observable universe" things are expanding at a measurable rate and should be backwards measurable to a specific point. My point was that physics seems to easily jump back and forth between the the "observable (real) universe" and various mathematically conceived universes and, in doing so, creates impossibilities. I realize that the mathematical "universes" are necessary to attempt predictability but physics seems to blur the difference between reality and theory in order to give pat answers. Because of this, physics seems to be chasing it's own tail.

I must disagree here, what cosmology does is to look at the OU and then to fit that into a standard cosmological mathematical model - the current model of best fit. Physics does not create mathematically conceived universes - it merely applies mathematical models to the existing OU and then assuming isotropy this can be applied to the entire U.

The universe can be traced backwards to a certain 'point' that being a point in space/time following t=0 but proceeding Planck time (not a physical location in 'space') If there was a 'point' in space where the big bang banged then U would not be homogenous. The physical attributes you are trying to apply would only apply to a 3d object expanding in an existing space, not taking into account any higher dimensions - not the totality of everything expanding.

For there to be a location where the big bang banged then the Universe would not be homogenous which according to best fit cosmological models is not the case.

CMB is the same in all directions.

 

[raynicolle]

You are right when you say physics uses mathematical models to attempt to predict and explain the OU. I should have said "imaginary mathematical models" instead of mathematical universes. You use "dimensions" and "points" to explain why there is no location in the OU where the Big Bang occured. Dimensions and points don't exist in the OU but planets and stars do. So, let me press the point by asking if the movements of the real objects in space (stars etc.) could be reversed then you would say that they would NOT come back together at one place even tho they should. Or you might say they do come back together at one place but they become "something else" than stars and planets...perhaps a black hole or dark matter/energy. Then, somehow, they disappear from the OU if you go back far enough in time. This irritates me because it sounds like Physics demands some kind of God or Prime Mover to explain the OU origin. A Prime Mover to "create" matter/energy out of nothing. A God or Prime mover to "invent" time. I just don't buy it. What I do think is that we have calculated the motion and direction of the stars in our little area of the OU and discount the idea that the universe is infinite and there are other areas of the OU that have stars traveling in the opposite directions. It just smells fishy to me. But I'm not a physicist.

 

[Cosmo Novice]

You are right when you say physics uses mathematical models to attempt to predict and explain the OU. I should have said "imaginary mathematical models" instead of mathematical universes. You use "dimensions" and "points" to explain why there is no location in the OU where the Big Bang occured. Dimensions and points don't exist in the OU but planets and stars do. So, let me press the point by asking if the movements of the real objects in space (stars etc.) could be reversed then you would say that they would NOT come back together at one place even tho they should. Or you might say they do come back together at one place but they become "something else" than stars and planets...perhaps a black hole or dark matter/energy. Then, somehow, they disappear from the OU if you go back far enough in time. This irritates me because it sounds like Physics demands some kind of God or Prime Mover to explain the OU origin. A Prime Mover to "create" matter/energy out of nothing. A God or Prime mover to "invent" time. I just don't buy it. What I do think is that we have calculated the motion and direction of the stars in our little area of the OU and discount the idea that the universe is infinite and there are other areas of the OU that have stars traveling in the opposite directions. It just smells fishy to me. But I'm not a physicist.

If we could go back in time approx 13.7GY assuming current observation then yes all the matter/energy in the OU and U in totality would come to a certain 'point' that point would be t=0. This is NOT a point in space but a point in time, space only exists when there is distance between matter and so prior to BB there was no 'point' in space for the BB to begin (the BB was the beginning of space, matter energy and time.) When you say physics demands something "create matter/energy out of nothing" you are assuming that prior to BB there was nothing - which is neither proved or disproved as when we trace back expansion all known Physics breaks down prior to Planck time and GR breaks down. This is where QM and gravity unification theory takes over - of which I know very little about but I understand this is a growing field - there are now a number of papers available on this which i am sure someone here could link for you.

All matter is expanding away from all other matter (for non gravity bound systems) ie: galaxies are all receeding away from each other, so to push the issue; if everything is receeding from everything else then geometrically WE are at the center of the BB. but if we could instantly travel to our closest galactic neighbour the same would be the case there (everything would be receeding and CMB would be the same in all directions) which would give us the impression that THERE was the center of the BB. Geometrically the BB began everywhere at once.

As stated I am not a pyhsicist so I am sure someone here can explain this a little better than me.

 

[phinds]

You are right when you say physics uses mathematical models to attempt to predict and explain the OU. I should have said "imaginary mathematical models" instead of mathematical universes. You use "dimensions" and "points" to explain why there is no location in the OU where the Big Bang occured. Dimensions and points don't exist in the OU but planets and stars do. So, let me press the point by asking if the movements of the real objects in space (stars etc.) could be reversed then you would say that they would NOT come back together at one place even tho they should. Or you might say they do come back together at one place but they become "something else" than stars and planets...perhaps a black hole or dark matter/energy. Then, somehow, they disappear from the OU if you go back far enough in time. This irritates me because it sounds like Physics demands some kind of God or Prime Mover to explain the OU origin. A Prime Mover to "create" matter/energy out of nothing. A God or Prime mover to "invent" time. I just don't buy it. What I do think is that we have calculated the motion and direction of the stars in our little area of the OU and discount the idea that the universe is infinite and there are other areas of the OU that have stars traveling in the opposite directions. It just smells fishy to me. But I'm not a physicist.

I strikes me that perhaps you might be causing some confusion for yourself by conflating the U and the OU. Although we cannot now, and may never be able to, say what's outside the OU, there is strong belief that the U just keeps on going and the effects of the BB are not confined to the OU. If the OU were all there is, that would have some truly weird effects on physics because then you WOULD have a "center" that the BB started from in space and that just doesn't make sense according to the current understands of cosmology. So your statement that the BB occurred in the OU implies a limit that isn't there. The BB occurred EVERYWHERE, including places that are not now in the OU. This is seriously weird stuff, but I think I have this right. I'm sure someone more knowledgeable will correct me if I don't.

 

[Cosmo Novice]

I strikes me that perhaps you might be causing some confusion for yourself by conflating the U and the OU. Although we cannot now, and may never be able to, say what's outside the OU, there is strong belief that the U just keeps on going and the effects of the BB are not confined to the OU. If the OU were all there is, that would have some truly weird effects on physics because then you WOULD have a "center" that the BB started from in space and that just doesn't make sense according to the current understands of cosmology. So your statement that the BB occurred in the OU implies a limit that isn't there. The BB occurred EVERYWHERE, including places that are not now in the OU. This is seriously weird stuff, but I think I have this right. I'm sure someone more knowledgeable will correct me if I don't.

No I understand that the OU is the distance that photons have been able to travel to us in 13.7GY and I understand that out past the OU cosmological models dictate the U is pretty much the same anywhere (even beyound our OU) as all galaxise would have their own OU and the only difference would be local variance. When I said that the BB began in our Galaxy and our galactic neighbour, I should have elaborated in saying this would be true of every galaxy in our OU and in the wider U assuming cosmological models are correct and U is homogenous with only local variance. That being the case the BB began everywhere all at once, as everything is receding from everything else. I totally agree with you, if you read my posts #26 and 27# with that in mind I am sure you will see i am in agreement with you.

Geometrically the BB began everywhere at once, as no matter what the topolgy, flat/curved, finite/non finite, the BB still began everywhere all at once and wherever you stand in the wider U thinks will look the same - everything will be receeding away from you as if you are the center and CMB will all look the same all coming at you from 13.7GY, all OUs will be 13.7GY :)

Pretty cool.

 

[phinds]

No I understand that the OU is the distance that photons have been able to travel to us in 13.7GY and I understand that out past the OU cosmological models dictate the U is pretty much the same anywhere (even beyound our OU) as all galaxise would have their own OU and the only difference would be local variance. When I said that the BB began in our Galaxy and our galactic neighbour, I should have elaborated in saying this would be true of every galaxy in our OU and in the wider U assuming cosmological models are correct and U is homogenous with only local variance. That being the case the BB began everywhere all at once, as everything is receding from everything else. I totally agree with you, if you read my posts #26 and 27# with that in mind I am sure you will see i am in agreement with you.

Geometrically the BB began everywhere at once, as no matter what the topolgy, flat/curved, finite/non finite, the BB still began everywhere all at once and wherever you stand in the wider U thinks will look the same - everything will be receeding away from you as if you are the center and CMB will all look the same all coming at you from 13.7GY, all OUs will be 13.7GY :)

Pretty cool.

Cosmo, I don't understand why you are interpreting what I said as having been directed at your post since I specificall quoted a different poster ... the same one you commented about.

 

[raynicolle]

in discussing the "size" of the universe I read in a post, "And because it is simply the distances between things, it doesn't need to have a boundary. It is too simple an idea to need a boundary or some other kind of "space" to live in. It can expand in a pure simple way without any of the usual accessories." I thought it was the things in the OU that gave it size...not the pure vacuum between those things. Not the distance...but the objects in conjunction with the distance.

Also, to have the OU expand from nothing (pure vacuum?) to its current size (assuming it is not infinite in size) without a time frame involved speaks of a god or a prime mover. I'm hoping Physics can do better than this semi-religious/magical theory.

To my mind, an infinitely large OU that was never "created" makes more sense than a Big Bang. I think that 13.7 GY may be a useful number in our little portion of the Big U. but it can be a set of blinders leading to the semi-religious/Prime Mover/Big Bang theory.

Either the OU is infinite in size or it isn't. If it is finite in size, then the eternal issue of what lies beyond the last observable "thing" comes back into play. If we can talk about "size" then we can talk about what lies beyond because size always has an edge in the OU. Maybe not in mathematical models of the OU, but in the real thing...size matters.

 

[phinds]

To my mind, an infinitely large OU that was never "created" makes more sense than a Big Bang. I think that 13.7 GY may be a useful number in our little portion of the Big U. but it can be a set of blinders leading to the semi-religious/Prime Mover/Big Bang theory.

Well, physics doesn't much care what you or I think. Current comosmological theory describes the big bang AFTER t=0, and does not require God

Either the OU is infinite in size or it isn't. If it is finite in size, then the eternal issue of what lies beyond the last observable "thing" comes back into play. If we can talk about "size" then we can talk about what lies beyond because size always has an edge in the OU. Maybe not in mathematical models of the OU, but in the real thing...size matters.

You need to look up "finite but unbounded" on the Internet

 

[raynicolle]

re."You need to look up "finite but unbounded" on the Internet"

The problem with the definitions of "finite but unbounded" is that they always rely on transference from 2D concepts through to 3D concepts. Example: a square has boundaries but a sphere does not...so the OU is a like a sphere and has no boundaries. That's garbage. There is no transference between dimensions. There isn't even any form of friction between dimensions. Spheres in the OU have boundaries because they are made of 'stuff'. Only spheres in mathematical models are boundry-less. Mathematical ants can crawl over a mathematical sphere for eternity and never find a boundary. But who cares? Real ants will find a boundary on a billiard ball very quickly. Again, there can be NO transference between dimensions in the OU. Only in math models. At least to my mind.

 

[raynicolle]

"Well, physics doesn't much care what you or I think. Current comosmological theory describes the big bang AFTER t=0, and does not require God"

Doesn't AFTER t=0 presuppose a t=0? I should think that the physics of the Big Bang would be very interested in t=0 and what kind of magic/god is connected to t=0 to create a Big Bang from pure vacuum.

Don't get me wrong. I love the idea of making Physics models to attempt to predict. I just think that Physics is barking up the wrong tree with the Big Bang. An infinitely sized OU that has existed forever makes more sense to this layman.

 

[Fredrik]

Doesn't AFTER t=0 presuppose a t=0?

That choice of words certainly suggests it, but it's just a poor choice of words. The original big bang theory is the statement that the large-scale behavior of the universe is described roughly by a FLRW solution of Einstein's equation. (That's the class of solutions that describes universes that are homogenous and isotropic). There's a standard way to assign coordinates to events in FLRW spacetimes, This assignment is such that the time coordinate of every event is positive. So there's no t=0 in the theory. The "big bang" is just a name for the limit t→0.

I should think that the physics of the Big Bang would be very interested in t=0 and what kind of magic/god is connected to t=0 to create a Big Bang from pure vacuum.

It's a mistake to think that there must have been a t=0. Yes, intuition tells us that there should be a t=0, but experiments have proved that our intuition about other properties of space and time are wrong, and they have failed to prove general relativity wrong. So it would be very naive to believe that human intuition is more reliable than the most accurate theory in science.

(Quantum mechanics might be more accurate, but we haven't figured out what it says about gravity yet).

There is no theory that says that something was created from nothing at t=0. Creationists are lying to you about that.

General relativity is a theory of space, time, and motion, that makes incredibly accurate predictions about a huge range of experiments. It's built up around an equation that describes the relationship between how matter is distributed and how it moves. All of the solutions that describe the large-scale distribution and motion of matter in a way that doesn't contradict what we see through telescopes have this property that we call "the big bang". The original big bang theory is just the claim that the large-scale behavior of the universe is described by one of those solutions.

Neither general relativity or its offspring "the big bang theory" is about creation.

I just think that Physics is barking up the wrong tree with the Big Bang. An infinitely sized OU that has existed forever makes more sense to this layman.

There wouldn't be any material left for nuclear fusion. So there wouldn't be any stars, at least not stars that still shine. Your hypothesis is also inconsistent with the redshift of distant galaxies. And it fails to predict the existence of background radiation. Those are just the first things I can think of. I'm sure the list can be made must longer.

 

[phinds]

The "big bang" is just a name for the limit t→0.

Yes, that is what I was attempting to say, and I believe I did imply it at least, but you have explained it much better. Thanks.

 

[Cosmo Novice]

Cosmo, I don't understand why you are interpreting what I said as having been directed at your post since I specificall quoted a different poster ... the same one you commented about.

My apologies I am totally blind :)

 

[WHATNOW]

I have an elementary understanding that the bang was an exspansion of space not an explosion of particles in space. This still does not help me understand why there cannot be a physical center to the universe. If the space is expanding at an increasing rate on all three axis; the X,Y and Z, in both the positive and negative directions on each. Then even if the partilces are not what is expanding there should still be a method for finding the center of the space. If there are methods to measure the exspansion rate of space which is ever increasing on all planes, why can this not be reversed at a corisponding level of decent to find the reletive center or origin?

 

[Mordred]

The expansion is even throughout. At every non gravational bound point the expansion rate is the same. So their is no way to distinquish a preferred direction of expansion.

Also their is no edge of spacetime. Regardless of if the universe is finite or infinite. You can never find an edge. So you cannot simply divide the diameter to find a center. Indeed

in both cases their need not be a center.
Look at the balloon analogy
sticky thread above for descriptions of how that works

The accurate way to think about it is Every point in spacetime is expanding in every direction. Point being any size you desire.

 

[Fredrik]

I have an elementary understanding that the bang was an exspansion of space not an explosion of particles in space. This still does not help me understand why there cannot be a physical center to the universe. If the space is expanding at an increasing rate on all three axis; the X,Y and Z, in both the positive and negative directions on each. Then even if the partilces are not what is expanding there should still be a method for finding the center of the space. If there are methods to measure the exspansion rate of space which is ever increasing on all planes, why can this not be reversed at a corisponding level of decent to find the reletive center or origin?

The thing you should try to understand isn't why there can't be a center, but why there doesn't have to be a center.

Imagine the pattern below extended to infinity in all directions. Now suppose that it's expanding at a constant rate, an increasing rate, or whatever rate you want it to. An observer that's comoving with any intersection of two lines could consider that point to be the center.