# size of our universe



## kev

I was watching an interesting series on the science channel about our universe (the one with Morgan Freeman - a little cheesy but whatever). One of the episodes was about our universe and whether it has an "edge" or whether it is infinite... or possibly as Einstein put it, "finite yet unbounded" (I think his words were something along those lines?) 

What do you guys think? Is there an edge to our universe, are there multiple universes, or is there just one infinite universe? Or is there another explanation entirely? 

Obviously the episode was dumbed down for the common viewer, so maybe there are some science geniuses who can explain the different theories to me. I just find this stuff fascinating for some reason.


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## Nathan Talli

I like M-theory. No way to test or prove it but it's fun to contemplate.


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## hoddesdon

It is a conundrum, in that it is difficult to imagine that something could have no end, yet if it does have an end, what lies beyond it? If you get to something that is beyond it, does that have an end, or is there something else again beyond it. So even if there is something beyond it, the same conundrum transfers to whatever that is.


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## Reinvented

If the universe is infinite, that means anything (and everything) that can happen, will happen somewhere. Therefore, the big bang has happened an infinite number of times, and there are an infinite number of people who are practically identical to you, living in distant parts of the universe.


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## Kon

27Anthony said:


> If the universe is infinite, that means anything (and everything) that can happen, will happen somewhere. Therefore, the big bang has happened an infinite number of times, and there are an infinite number of people who are practically identical to you, living in distant parts of the universe.


Maybe not. Consider this analogy from another post in a physics forum:

"The set of all even numbers is infinite. I can go on counting even numbers for ever and ever and never reach an end. But clearly the set of all even numbers does not include all possible numbers. It doesn't include, for instance, the number pi. So even if the universe is infinite (we don't know whether or not it is), then that doesn't necessarily mean that all possibilities are realized.

However, there may be other reasons to believe that all possibilities are realized, mainly stemming from quantum mechanics, where we find, for instance, that if there is the possibility of matter inhabiting a region of space, then particles of that sort of matter will necessarily pop in and out of the vacuum. Another way of saying this is that in quantum mechanics, the mere _possibility_ of existence forces existence. So it is not unreasonable to suspect that perhaps all possibilities must actually be realized.

This doesn't mean that anything and everything we can imagine occurs, of course. We can imagine quite a lot of impossible things... But we can also imagine a great many things that are not obviously impossible, and yet may turn out to be upon deeper inspection."



kev said:


> Is there an edge to our universe?


*What is the Universe expanding into?*

"This question is based on the ever popular misconception that the Universe is some curved object embedded in a higher dimensional space, and that the Universe is expanding into this space. This misconception is probably fostered by the balloon analogy which shows a 2-D spherical model of the Universe expanding in a 3-D space. While it is possible to think of the Universe this way, it is not necessary, and there is nothing whatsoever that we have measured or can measure that will show us anything about the larger space. _Everything that we measure is within the Universe, and we see no edge or boundary or center of expansion._

Thus the Universe is not expanding into _anything_ that we can see, and this is not a profitable thing to think about. Just as Dali's Corpus Hypercubicus is just a 2-D picture of a 3-D object that represents the surface of a 4-D cube, remember that the balloon analogy is just a 2-D picture of a 3-D situation that is supposed to help you think about a curved 3-D space, but it does not mean that there is really a 4-D space that the Universe is expanding into."


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## Reinvented

Kon said:


> Maybe not. Consider this analogy from another post in a physics forum:
> 
> "The set of all even numbers is infinite. I can go on counting even numbers for ever and ever and never reach an end. But clearly the set of all even numbers does not include all possible numbers. It doesn't include, for instance, the number pi. So even if the universe is infinite (we don't know whether or not it is), then that doesn't necessarily mean that all possibilities are realized.


I understand what you are saying (that not all infinities are the same), but I just can't fathom how some possibilities could exist, and not others in an infinite universe. It doesn't make sense to me. If something is possible then surely it must exist, given infinite time and space.

Have you heard of the infinite monkey theorem? From wikipedia: "a monkey hitting keys at random on a typewriter keyboard for an infinite amount of time will almost surely type a given text, such as the complete works of William Shakespeare." http://en.wikipedia.org/wiki/Infinite_monkey_theorem


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## ugh1979

hoddesdon said:


> It is a conundrum, in that it is difficult to imagine that something could have no end, yet if it does have an end, what lies beyond it? If you get to something that is beyond it, does that have an end, or is there something else again beyond it. So even if there is something beyond it, the same conundrum transfers to whatever that is.


 Asking what is 'beyond' or 'before' is something that is very natural and obvious to us as humans, but they simply aren't valid questions when it comes to subjects like this as they move beyond the time and space that we are familar with. It's like asking where a circle starts, or something that only exists on an XY 2D surface asking what is in the Z dimension. It simply isn't part of their existence so can't be comprehended.

It's something that is best understood and managed with mathematics. It can't mentally/visually be imagined as our brains simply can't comprehend more than 3 spacial dimensions.

A sense of time and space could just be how we interpret and understand the cosmos, when in fact everything that could ever happen anywhere is all simultaneously happening now.


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## ugh1979

kev said:


> I was watching an interesting series on the science channel about our universe (the one with Morgan Freeman - a little cheesy but whatever). One of the episodes was about our universe and whether it has an "edge" or whether it is infinite... or possibly as Einstein put it, "finite yet unbounded" (I think his words were something along those lines?)
> 
> What do you guys think? Is there an edge to our universe, are there multiple universes, or is there just one infinite universe? Or is there another explanation entirely?
> 
> Obviously the episode was dumbed down for the common viewer, so maybe there are some science geniuses who can explain the different theories to me. I just find this stuff fascinating for some reason.



Multiverses are the generally favoured theory in current physics. There are various different multiverse theories though.

One of our best, if not the best, current theories of everything is string theory, and it indicates multiverses, (along with there being up to 11 dimensions), so it has some good evidence behind it. 

 For the record M-Theory, as someone mentioned, is a theory that encompasses many of the different string theories.

 It's a hell of a subject to get in to briefly on a forum, and a wealth of reading and understanding is required to even start to get your head round it.

 As you say though, it's a fascinating subject.


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## Kon

ugh1979 said:


> Asking what is 'beyond' or 'before' is something that is very natural and obvious to us as humans, but they simply aren't valid questions when it comes to subjects like this as they move beyond the time and space that we are familar with.


And yet, it is something that is being asked by the physics community itself:

See 1:20 seconds into program of first video link where some physicists at Perimeter Institute are polled/asked about whether there was a "before the big bang":






http://www.perimeterinstitute.ca/News/In_The_Media/What_Happened_Before_The_Big_Bang?/


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## coldsorehighlighter

The Universe is a mind-****.


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## ugh1979

Kon said:


> And yet, it is something that is being asked by the physics community itself:
> 
> See 1:20 seconds into program of first video link where some physicists at Perimeter Institute are polled/asked about whether there was a "before the big bang":
> 
> 
> 
> 
> 
> 
> http://www.perimeterinstitute.ca/News/In_The_Media/What_Happened_Before_The_Big_Bang?/


Well they obviously ask it, but that's due to the reasons I gave, as it's such a natural thing to do and one of the first things people ask or think about. However the scientists in the documentary's you linked to give much the same answer I did.


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## zookeeper




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## estse

The universe is 10% of your brain.


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## ugh1979

Mercurochrome said:


> The universe is 10% of your brain.


?


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## sas111

Even if there is an end to the universe, then what would that look like? A blank canvas, a giant wall of darkness, fire, then what would be behind the the wall? You know? Possibly a whole nother universe with a complete different looking galaxy & strange creatures, wondering the exact same thing. Then what's beyond that universe? ANOTHER one! :teeth


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## 0lly

Kon said:


> However, there may be other reasons to believe that all possibilities are realized, mainly stemming from quantum mechanics, where we find, for instance, that if there is the possibility of matter inhabiting a region of space, then particles of that sort of matter will necessarily pop in and out of the vacuum. Another way of saying this is that in quantum mechanics, the mere _possibility_ of existence forces existence. So it is not unreasonable to suspect that perhaps all possibilities must actually be realized.
> 
> "


I've been studying Theoretical Physics at university for two years now, I'm far from being an expert but my understanding so far is this:

The route cause of all events in the universe is dictated by the apparent random quantum events. For instance an electron may be said to be everywhere in the universe, with its probability of being found in anyone place dictated by its probability distribution (or wave function).

Importantly though, until an observation of its location is made it IS everywhere; its a superposition of all possible states. But when the observation is made, the probability function collapses (its unknown why) to a single certain real location. However, according to the standard model, when that decision is made, our time line splits up to and follows an infinite number other branches to allow for the other possibilities.

That is to say that the time line isn't 'straight'; it's all branched out and undulating in the higher time dimensions. I think lol.


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## 0lly

It's also worth saying that its thought that there are infinite other universes (separated from us by non-spacial dimensions). This would allow for other universes to exist in states differing from our own universe. i.e things could happen in those different universes which would not be allowed in ours. Perhaps no law of gravity for instance.

Each universe would contain all its possible time lines and outcomes.


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## ugh1979

Yes 0lly, that is my general understanding of the current favoured theories at present as well.

As you say, until observation is made (or interaction, which also forces a particle to settle from its superposition), a particle could be considered to be 'every where'. It could also be considered to be 'every when'.


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## 0lly

Actually I'm not sure if they can be considered everywhen. That might mean that in the electron double-slit experiment, an electron could arrive at the detector before its left its source, which would violate Special Relativity. Or maybe I've just confused myself; I mean the probability distributions are indeed time dependent.


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## ugh1979

0lly said:


> Actually I'm not sure if they can be considered everywhen. That might mean that in the electron double-slit experiment, an electron could arrive at the detector before its left its source, which would violate Special Relativity. Or maybe I've just confused myself; I mean the probability distributions are indeed time dependent.


But 'before' is only relative to the observer.


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## 0lly

ugh1979 said:


> But 'before' is only relative to the observer.


No I think before is before. Everything observes cause and effect, I can't think how you would observe otherwise.

On another note, relating to the overall structure of the Universe, this video explains quite well some of the current concepts of the Universe, without going into Quantum Mechanics (you may have already seen it though).


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## ugh1979

0lly said:


> No I think before is before. Everything observes cause and effect, I can't think how you would observe otherwise.


Time as we know it doesn't exist out with space, so if you are observing from out with our universe then the concept of a before could be invalid. I believe ultimately the cosmos only exists 'now', and it's only when you go down to lower dimensional levels, in for example individual universes, time exists and the concept of a before becomes valid to any observer within that universe.



> On another note, relating to the overall structure of the Universe, this video explains quite well some of the current concepts of the Universe, without going into Quantum Mechanics (you may have already seen it though).


I've not seen that one but I've seen many.


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## 0lly

ugh1979 said:


> I believe ultimately the cosmos only exists 'now', and it's only when you go down to lower dimensional levels, in for example individual universes, time exists and the concept of a before becomes valid to any observer within that universe.


But of course Quantum Mechanics, for instance the Schrodinger eqns, rely on space and time and those lower dimensions.


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## Kon

0lly said:


> Importantly though, until an observation of its location is made it IS everywhere; its a superposition of all possible states. But *when the observation is made*, *the probability function collapses (its unknown why) to a single certain real location.* However, according to the standard model, *when that decision is made*, our time line splits up to and follows an infinite number other branches to allow for the other possibilities.That is to say that the time line isn't 'straight'; it's all branched out and undulating in the higher time dimensions. I think lol.


I never understood that. When there are "measurements" occurring, the states of the measured systems evolve not in accordance with the dynamical equations of motion but instead, in accordance with the postulate of collapse. Not only does this collapse occur instantaneously upon measurement, but the measurement act itself is ambiguous since it is unclear exactly when a measurement has occured.

If one assumes that it occurs at some macroscopic level, then, where does one draw this "cut" between the micro-macro domain? Even if one assumes that a macroscopic system can somehow collapse the wave function, other difficulties arise: is not the macroscopic system (i.e. apparatus, observer, etc.) itself composed of the very same sort of microscopic objects that the apparatus or observer is supposed to collapse (i.e. particles subject to quantum effects)? ...Schrodinger's cat.

Even is one accepts the mathematical formalism of QM as is and assumes that the wave function never "collapses", what sort of things constitute a measurement-like interaction allowing the universe to split into these branches?


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## 0lly

Kon said:


> is not the macroscopic system (i.e. apparatus, observer, etc.) itself composed of the very same sort of microscopic objects that the apparatus or observer is supposed to collapse (i.e. particles subject to quantum effects)? ...Schrodinger's cat.


Of course but the larger somethings mass, the more certain we can be of its properties; its de Broglie wavelength decreases. This wavelength is the probability wave. We are built up of subatomic particles and these are indeed more indistinct.

As for what constitutes an observation, and how observations can be made by things which are themselves indistinct, I not certain enough to commit to an answer lol. I need to go away and read my text books again! I'll try and come back with a decent answer soon.


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## 0lly

In the mean time here's a quite a nice quote from Cormac McCarthy's Blood Meridian that resembles the complexities of Quantum Mechanics lol:

*"every man is tabernacled in every other and he in exchange and so on in an endless complexity of being and witness to the uttermost edge of the world"*

Actually that sort of applies to social anxiety too lol.


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## ugh1979

Kon said:


> I never understood that. When there are "measurements" occurring, the states of the measured systems evolve not in accordance with the dynamical equations of motion but instead, in accordance with the postulate of collapse. Not only does this collapse occur instantaneously upon measurement, but the measurement act itself is ambiguous since it is unclear exactly when a measurement has occured.
> 
> If one assumes that it occurs at some macroscopic level, then, where does one draw this "cut" between the micro-macro domain? Even if one assumes that a macroscopic system can somehow collapse the wave function, other difficulties arise: is not the macroscopic system (i.e. apparatus, observer, etc.) itself composed of the very same sort of microscopic objects that the apparatus or observer is supposed to collapse (i.e. particles subject to quantum effects)? ...Schrodinger's cat.
> 
> Even is one accepts the mathematical formalism of QM as is and assumes that the wave function never "collapses", what sort of things constitute a measurement-like interaction allowing the universe to split into these branches?


That's a good and interesting QM question.

My current rough understanding is that it's from 2 particles interactions upwards. The interaction of the 2 particles is enough to drop them out of their superposition and possibly start the snowballing effect of becoming a less fundamental object.


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## THEuTASTEsOFeINKd

Thinkin about the universe makes me super depressed. It's best not to think too much about how insignificant you really are. **** sanity.


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## fatelogic

That is just playing hide and go seek. just keep playing but don't feel like science answers all of your questions... you would not have SA if science had all the answers IMO. i just see that as entertainment. i mean, the number 0 (or -0) basically means the beginning of time (or that everything comes from nothing). it means the big bang. though the big bang is just a theory... science channels just love to jump the gun for revenue... 10 years from now, they will change their logic though and so will you.

you could say i "love" science though... because i like playing that game. fck athiests though.


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## ugh1979

THEuTASTEsOFeINKd said:


> Thinkin about the universe makes me super depressed. It's best not to think too much about how insignificant you really are. **** sanity.


Sorry to hear that.

I have no problem grounding myself with the fact I'm not special or significant, and simply enjoy the wonder and beauty of reality during my current existence.


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## ugh1979

fatelogic said:


> That is just playing hide and go seek. just keep playing but don't feel like science answers all of your questions... you would not have SA if science had all the answers IMO. i just see that as entertainment.


What/who is playing hide an go seek?

Who is professing that science has all the answers? There are more questions still to be answered than have even been asked.



> i mean, the number 0 (or -0) basically means the beginning of time. it means the big bang. though the big bang is just a theory


So the number 0 means has no other meaning other than to signify the big bang? 0 is a concept that can be applied to many things.



> ... science channels just love to jump the gun... 10 years from now, they will change their logic though.


'Jumping the gun' is fundamental to the scientific process. You must speculate before you can experiment and prove theories, then in turn adapt logic as more knowledge is gained. It's a wonderful infallible system.


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## Kon

I thought this was kind of on topic:

*Is our universe inside a bubble? First observational test of the multiverse*

August 7, 2011

ScienceDaily (Aug. 3, 2011) - The theory that our universe is contained inside a bubble, and that multiple alternative universes exist inside their own bubbles -- making up the 'multiverse' -- is, for the first time, being tested by physicists. Two research papers published in _Physical Review Letters_ and _Physical Review D_ are the first to detail how to search for signatures of other universes. Physicists are now searching for disk-like patterns in the cosmic microwave background (CMB) radiation -- relic heat radiation left over from the Big Bang -- which could provide tell-tale evidence of collisions between other universes and our own.

Many modern theories of fundamental physics predict that our universe is contained inside a bubble. In addition to our bubble, this `multiverse' will contain others, each of which can be thought of as containing a universe. In the other 'pocket universes' the fundamental constants, and even the basic laws of nature, might be different.

Until now, nobody had been able to find a way to efficiently search for signs of bubble universe collisions -- and therefore proof of the multiverse -- in the CMB radiation, as the disc-like patterns in the radiation could be located anywhere in the sky. Additionally, physicists needed to be able to test whether any patterns they detected were the result of collisions or just random patterns in the noisy data.

A team of cosmologists based at University College London (UCL), Imperial College London and the Perimeter Institute for Theoretical Physics has now tackled this problem. "It's a very hard statistical and computational problem to search for all possible radii of the collision imprints at any possible place in the sky," says Dr Hiranya Peiris, co-author of the research from the UCL Department of Physics and Astronomy. "But that's what pricked my curiosity."

The team ran simulations of what the sky would look like with and without cosmic collisions and developed a ground-breaking algorithm to determine which fit better with the wealth of CMB data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP). They put the first observational upper limit on how many bubble collision signatures there could be in the CMB sky.

Stephen Feeney, a PhD student at UCL who created the powerful computer algorithm to search for the tell-tale signatures of collisions between "bubble universes," and co-author of the research papers, said: "The work represents an opportunity to test a theory that is truly mind-blowing: that we exist within a vast multiverse, where other universes are constantly popping into existence."

One of many dilemmas facing physicists is that humans are very good at cherry-picking patterns in the data that may just be coincidence. However, the team's algorithm is much harder to fool, imposing very strict rules on whether the data fits a pattern or whether the pattern is down to chance.

Dr Daniel Mortlock, a co-author from the Department of Physics at Imperial College London, said: "It's all too easy to over-interpret interesting patterns in random data (like the 'face on Mars' that, when viewed more closely, turned out to just a normal mountain), so we took great care to assess how likely it was that the possible bubble collision signatures we found could have arisen by chance."

The authors stress that these first results are not conclusive enough either to rule out the multiverse or to definitively detect the imprint of a bubble collision. However, WMAP is not the last word: new data currently coming in from the European Space Agency's Planck satellite should help solve the puzzle.

*Journal References*:

Stephen M. Feeney, Matthew C. Johnson, Daniel J. Mortlock, Hiranya V. Peiris. *First Observational Tests of Eternal Inflation: Analysis Methods and WMAP 7-Year Results*. _Physical Review D_, 2011; (in press)
Stephen M. Feeney, Matthew C. Johnson, Daniel J. Mortlock, Hiranya V. Peiris. *First observational tests of eternal inflation*. _Physical Review Letters_, 2011; (accepted)
http://www.sciencedaily.com/releases/2011/08/110803102844.htm


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## fatelogic

the universe does not have an edge because it is round. the earth's shape could be thought as the universe. the earth has no edge in that regard. so if by edge they mean the radius of the roundness, so i guess our universe has a distance from the center to the perimeter... but technically it has no edge.

edit: i didn't know i had posted here already, ah well.


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## fatelogic

> So the number 0 means has no other meaning other than to signify the big bang? 0 is a concept that can be applied to many things.


 hmmmm.... you are not thinking outside the box for the simple fact that the number 0 states nothing. e.g. if you have 0 money, you have nothing money. of course, the number 0 only exists in the math universe.

The big bang is assume to bang from nothing... actually they state that it starts from something - a 0 and a -0... seriously, the 0 itself cannot be a 0 from nothing, the number 0 is something itself.

What was you point about saying that because you where not very clear about it?


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## hoddesdon

fatelogic said:


> the universe does not have an edge because it is round.


How do you know it is round?


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## fatelogic

^because everything that bangs, bangs outwards in every direction... like blowing up a balloon.

edit: i am not trying to teach but rather provoke someone to keep searching deeper. e.g. the universe cannot exist if there is no space. so a balloon can only be blown up where space exists already. the big bang cannot bang where there is no space. where did space come from? or what is space? for example... if i want to go deeper past the big bang THEORY... so the big bang cannot come from nothing if space is something.


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## Reinvented

The big bang does not necessarily determine the shape of the universe.


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## Kon

ugh1979 said:


> That's a good and interesting QM question.
> 
> My current rough understanding is that it's from 2 particles interactions upwards. The interaction of the 2 particles is enough to drop them out of their superposition and possibly start the snowballing effect of becoming a less fundamental object.


So I'm guessing this is what you mean?

*Line Between Quantum And Classical Worlds Is At Scale Of Hydrogen Molecule*

"If the two-electron system is split into its subsytems and one (the "observer") is thought of as the environment of the other, it becomes evident that classical properties such as loss of coherence can emerge even when only four particles (two electrons, two protons) are involved."

http://www.sciencedaily.com/releases/2007/11/071109090639.htm


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## hoddesdon

fatelogic said:


> ^because everything that bangs, bangs outwards in every direction... like blowing up a balloon.
> 
> edit: i am not trying to teach but rather provoke someone to keep searching deeper. e.g. the universe cannot exist if there is no space. so a balloon can only be blown up where space exists already. the big bang cannot bang where there is no space. where did space come from? or what is space? for example... if i want to go deeper past the big bang THEORY... so the big bang cannot come from nothing if space is something.


I think the official scientific position at the moment is that before the Big Bang there was no space. Certainly before the Big Bang there was no time, so asking what existed before the Big Bang is a non-question, since "before" is a property of time. Since space and time are connected - hence the "space-time continuum" - it is not true that space already existed.


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## ugh1979

fatelogic said:


> hmmmm.... you are not thinking outside the box for the simple fact that the number 0 states nothing.


You were far from clear in you initial post, hence why I asked you. It wasn't a case of thinking outside the box.



> e.g. if you have 0 money, you have nothing money. of course, the number 0 only exists in the math universe.
> 
> The big bang is assume to bang from nothing... actually they state that it starts from something - a 0 and a -0... seriously, the 0 itself cannot be a 0 from nothing, the number 0 is something itself.
> 
> What was you point about saying that because you where not very clear about it?


What point was I saying? You're not being very clear.


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## ugh1979

fatelogic said:


> ^because everything that bangs, bangs outwards in every direction... like blowing up a balloon.
> 
> edit: i am not trying to teach but rather provoke someone to keep searching deeper. e.g. the universe cannot exist if there is no space. so a balloon can only be blown up where space exists already. the big bang cannot bang where there is no space. where did space come from? or what is space? for example... if i want to go deeper past the big bang THEORY... so the big bang cannot come from nothing if space is something.


Not true.

Think of a virtual universe created in a computer. The virtual space with it doesn't require a virtual space out with it.


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## ugh1979

Kon said:


> So I'm guessing this is what you mean?
> 
> *Line Between Quantum And Classical Worlds Is At Scale Of Hydrogen Molecule*
> 
> "If the two-electron system is split into its subsytems and one (the "observer") is thought of as the environment of the other, it becomes evident that classical properties such as loss of coherence can emerge even when only four particles (two electrons, two protons) are involved."
> 
> http://www.sciencedaily.com/releases/2007/11/071109090639.htm


Yes.


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## ugh1979

max4225 said:


> This universe is about 10^103 cubic light years. There is no edge. If you could travel at nearly infinite speed in a mostly straight line for 5x10^33 light years you'll end up back where you started from.


Indeed, which is why we can think of the universe as existing on the surface of a bubble, rather than within it.


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## Kon

hoddesdon said:


> I Certainly before the Big Bang there was no time, so asking what existed before the Big Bang is a non-question, since "before" is a property of time. Since space and time are connected - hence the "space-time continuum" - it is not true that space already existed.


I suppose one can re-word it and ask what caused the big bang?


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## hoddesdon

Tugwahquah said:


> My universe is within the boundry of my property. The rest is too mindboggling.


My mind boggled a long time ago.


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## rockyraccoon

If the universe is infinite in size then isn't any point in the universe the centre of the universe? Isn't that what relativity tells us? Could I not say that me sitting at my computer right now is the centre of the universe since the universe doesn't have an edge or boundary to it because the universe goes on to infinity? (Assuming one believes the universe to not be finite but infinite?)


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## Kon

rockyraccoon said:


> If the universe is infinite in size then isn't any point in the universe the centre of the universe? Isn't that what relativity tells us? Could I not say that me sitting at my computer right now is the centre of the universe since the universe doesn't have an edge or boundary to it because the universe goes on to infinity? (Assuming one believes the universe to not be finite but infinite?)


Even if the universe is finite, there's likely no such thing as the centre:

*Where did the Big Bang happen? Would that be the center of the universe?*

According to standard cosmological models, which are based on general relativity and are found to agree well with observations, time and space did not exist before the Big Bang -- or even _at _the time of the Big Bang, which is a point where the theory breaks down because various quantities (such as temperature and spacetime curvature) are infinite. Therefore these models do not describe the Big Bang as an explosion that happened at a particular point in a preexisting landscape of time and space.

These are only statements about a particular kind of model. The model incorporates various assumptions, and as we get closer and closer to the Big Bang, these assumptions become more and more uncertain. *For example, it is possible that under conditions of very high density and temperature, matter has exotic behavior that causes gravity to become repulsive. If this happens, then it's possible that the Big Bang was not a bang but a bounce, and then time could be extended farther back into the past.*

*But even if time existed before the Big Bang, there is still another reason not to imagine the Big Bang as happening at one point in a preexisting empty space.* Observations of the universe show a nearly complete lack of structure on very large scales, and the cosmic microwave background is also extremely uniform (with fractional temperature differences on the order of 10-5). For this reason, realistic cosmological models must be almost exactly homogeneous, meaning that no point in space has properties that differ very much from those of any other point. Therefore the best evidence is that the Big Bang happened uniformly, everywhere at once.

Since realistic cosmological models are homogeneous, every point in space has the same properties as every other point, and therefore the models don't have a center. We can visualize this using the metaphor in which galaxies are dots on a balloon being blown up. No point on the balloon is the center of expansion. If you want to pick out a center, you have to pick a point in the air, not on the surface of the balloon. But in the balloon analogy, the third dimension is just an aid to visualization. Only points on the balloon's two-dimensional surface represent actual points in space.

http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf

http://www.physicsforums.com/showthread.php?t=506991


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## ugh1979

> We can visualize this using the metaphor in which galaxies are dots on a balloon being blown up. No point on the balloon is the center of expansion. If you want to pick out a center, you have to pick a point in the air, not on the surface of the balloon. But in the balloon analogy, the third dimension is just an aid to visualization. Only points on the balloon's two-dimensional surface represent actual points in space.


Great analogy.


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## Kon

ugh1979 said:


> Great analogy.


I find that if I think of time as analogous to the the diameter of a expanding balloon, it helps me visualize it better. So the "edge" of the universe also makes no sense because at present we are at the edge also because every point of the expanding balloon at a given time is the "edge" in some sense.Think of the rubber of the balloon. At any given diameter every point of the balloon is the edge of this 2-D structure. Same thing with our universe except for having more dimensions.


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## fatelogic

> If you could travel at nearly infinite speed in a mostly straight line for 5x10^33 light years you'll end up back where you started from.


 that is wrong because the universe does not have an outer shell let alone no center gravitational pull... hence everything is moving outward.

So you are telling me if I was to go in a mostly straight line towards the direction of where the big bang occurred (or the opposite way, or towards any random direction for that matter), I would end up in the same location? Like if I was to drill my way down on earth I would end up here again? Explain.


----------



## Kon

Kon said:


> _So I'm guessing this is what you mean?_
> 
> _*Line Between Quantum And Classical Worlds Is At Scale Of Hydrogen Molecule*_
> 
> _"If the two-electron system is split into its subsytems and one (the "observer") is thought of as the environment of the other, it becomes evident that classical properties such as loss of coherence can emerge even when only four particles (two electrons, two protons) are involved."_
> 
> _[URL]http://www.sciencedaily.com/releases...1109090639.htm_ [/URL]





ugh1979 said:


> Yes.


As far as I understand it, the results of this and similar experiments on *decoherence* do not solve the measurement problem as outlined below:

"A stronger claim is that decoherence is not only relevant to this question but by itself already provides the complete answer. In the special case of measuring apparatus, it would explain why we never observe an apparatus pointing, say, to two different results, i.e., decoherence would provide a solution to the measurement problem. As pointed out by many authors, however, this claim is not tenable. Thus, decoherence as such does not provide a solution to the measurement problem, at least not unless it is combined with an appropriate interpretation of the wave function."

http://plato.stanford.edu/entries/qm-decoherence/

"Decoherence shows how a macroscopic system interacting with a lot of microscopic systems (e.g. collisions with air molecules or photons) moves from being in a pure quantum state-which in general will be a coherent superposition (see Schrödinger's cat)-to being in an incoherent mixture of these states. The weighting of each outcome in the mixture in case of measurement is exactly that which gives the probabilities of the different results of such a measurement. However, decoherence by itself may not give a complete solution of the measurement problem, since all components of the wave function still exist in a global superposition, which is explicitly acknowledged in the many-worlds interpretation. All decoherence explains, in this view, is why these coherences are no longer available for inspection by local observers."

"Decoherence does not provide a mechanism for the actual wave function collapse; rather it provides a mechanism for the appearance of wavefunction collapse. The quantum nature of the system is simply "leaked" into the environment so that a total superposition of the wavefunction still exists, but exists - at least for all practical purposes- beyond the realm of measurement."

http://en.wikipedia.org/wiki/Quantum_decoherence

"In brief, the entanglement brought about by interaction with the environment could even be considered as making the measurement problem worse. Bacciagaluppi (2003) puts it like this:

Intuitively, if the environment is carrying out, without our intervention, lots of approximate position measurements, then the measurement problem ought to apply more widely, also to these spontaneously occurring measurements. (. . . ) The state of the object and the environment could be a superposition of zillions of very well localised terms, each with slightly different positions, and which are collectively spread over a macroscopic distance, even in the case of everyday objects. (. . . ) If everything is in interaction with everything else, everything is entangled with everything else, and that is a worse problem than the entanglement of measuring apparatuses with the measured probes.​ 
http://arxiv.org/PS_cache/quant-ph/pdf/0312/0312059v4.pdf


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## ugh1979

fatelogic said:


> that is wrong because the universe does not have an outer shell let alone no center gravitational pull... hence everything is moving outward.
> 
> So you are telling me if I was to go in a mostly straight line towards the direction of where the big bang occurred (or the opposite way, or towards any random direction for that matter), I would end up in the same location? Like if I was to drill my way down on earth I would end up here again? Explain.


Think about travelling from 1 point on the surface of an expanding balloon all the way round it until you got back to the same point you started.

That is just one theory. There are obviously many others.


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## fatelogic

> Think about travelling from 1 point on the surface of an expanding balloon all the way round it until you got back to the same point you started.


 I've already thought beyond that simple logic.

The only way that would add up is if there is an outer "layer" of space in the universe where galaxy clusters and galaxy cluster clusters only stay in. So no galaxies can go inward past this "invisible force" to the center of the universe.

And that does not even add up because we don't even know where the center of the universe is. So we cannot now if we are in the outer most edge of the universe. Heck, we may be really close to the center of the universe.

If you were to be living in another earth in another galaxy, and look up the sky with your million dollars telescope, you would still see the galaxies "expanding" too. Like we see here in earth. So they/we don't know in what place of the universe we are at... let alone if we go this way or that way in space, we end up back here.

So I've already though past beyond that logic. Besides that sounds like something that people use to believe back when, when they use to believe the earth was flat or that planets revolved around earth.



> That is just one theory. There are obviously many others.


 At what school are they teaching this theory?


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## fatelogic

I am delayed in responding to this 'cause the site was down. At any rate...



> I think the official scientific position at the moment is that before the Big Bang there was no space.


 I didn't know this but thanks for pointing this out... so what do you call the spot/place/void/nothingness where the energy was gathering ready to bang?



> Certainly before the Big Bang there was no time, so asking what existed before the Big Bang is a non-question, since "before" is a property of time.


 so it didn't take time for the energy to gather to bang?



> Since space and time are connected - hence the "space-time continuum" - it is not true that space already existed.


 yeah that way of thinking just gives our curious brains an excuse to satisfy it because we can stop wondering at things we cannot understand.

Thinking this way is beautiful for scientists?

Dark energy = 0
dark matter = 0
gravity = 0
big bang = 0
super massive black holes = 0

by that logic, why do they get mad when GOD = 0 too... didn't want to bring religion in here just came to my mind.

But anyway, how can there not be any space before the big bang, since the big bang was started due to some gases collecting. Where was the gas floating around on? Pink energy? From what I understand, the big bang started from a collection of gases and other things.


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## ugh1979

fatelogic said:


> I've already thought beyond that simple logic.
> 
> The only way that would add up is if there is an outer "layer" of space in the universe where galaxy clusters and galaxy cluster clusters only stay in. So no galaxies can go inward past this "invisible force" to the center of the universe.
> 
> And that does not even add up because we don't even know where the center of the universe is. So we cannot now if we are in the outer most edge of the universe. Heck, we may be really close to the center of the universe.
> 
> If you were to be living in another earth in another galaxy, and look up the sky with your million dollars telescope, you would still see the galaxies "expanding" too. Like we see here in earth. So they/we don't know in what place of the universe we are at... let alone if we go this way or that way in space, we end up back here.
> 
> So I've already though past beyond that logic. Besides that sounds like something that people use to believe back when, when they use to believe the earth was flat or that planets revolved around earth.
> 
> At what school are they teaching this theory?


:lol

Trust me, it's a theory that's been proposed by prominent modern physicists. I read about this kind of thing all the time so am familiar with a lot of them.

You need to literally think outside the box and abandon the familiar 3 spacial dimensions your thinking is trapped in.

You seem like you are keen to learn about all this so I suggest you go and do some reading up on it or watching some good documentaries on the subject which will do a better job that us of explaining these challenging theories.


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## fatelogic

^ok you believe you know .. tell me within 5 minutes, 

why do galaxies cluster? 

and why do galaxies don't fall apart since the gravitational pull is too weak to keep them together?

go! you have 4 minutes and 59 seconds left...


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## fatelogic

Let me educate myself from the interwebs...



> *What is the Big Bang?*
> According to the big bang theory, [1]*the universe began by expanding from an infinitesimal volume with extremely high density and temperature.* [2]*The universe was initially significantly smaller than even a pore on your skin.* [3]*With the big bang, the fabric of space itself began expanding like the surface of an inflating balloon* - matter simply rode along the stretching space like dust on the balloon's surface.


what does the bold statements really mean? 

[1] infinitesimal- *Infinitesimals* have been used to express the idea of objects so small that there is no way to see them or to measure them.

[2] the universe was smaller than pore on my nose?

[3] hmmm... the big bang expanded the fabric of space. Ok, to me that implies space was there before the big bang... I am learning.

http://www.ugcs.caltech.edu/~yukimoon/BigBang/


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## 0lly

Hmm, I was going to post a reply to this thread but I'm not entirely sure what it's about anymore. 

Are we discussing the different interpretations of wavefunctions, the big bang, or cosmology more generally? Perhaps a thread for each? I might start a thread about interpretations of Quantum Mechanics, it might help me get a few things straight in my head, although I need to finish doing some serious reading first.


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## hoddesdon

Kon said:


> According to standard cosmological models, which are based on general relativity and are found to agree well with observations, time and space did not exist before the Big Bang -- or even _at _the time of the Big Bang


 Isn't saying that time did not exist at the time of the Big Bang a paradox?


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## Reinvented

0lly said:


> Hmm, I was going to post a reply to this thread but I'm not entirely sure what it's about anymore.
> 
> Are we discussing the different interpretations of wavefunctions, the big bang, or cosmology more generally?


This thread IS the big bang.


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## Kon

hoddesdon said:


> Isn't saying that time did not exist at the time of the Big Bang a paradox?


From my understanding what this means is that their models say nothing about t = 0 or t < 0. At t=0, the laws of physics that we are familiar with cease to apply, and that includes causality since causality in physics doesn't make sense without time, I think? How does one possibly get around this?

"One relevant point is that even in a universe that has existed for a finite proper time, there are still an infinite number of events in any arbitrary interval near 0. So even there, all events have a cause-in fact, an infinite chain of causes (at least if we exclude the single point at t=0)...Even if the proper time is finite, it might be that whatever kind of clock you care most about ticks faster and faster as you approach the big bang, in such a way that it ticks an infinite number of times "before" you arrive there. In that case, the universe is effectively eternal."


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## roughh

I'm so not a _science genius_or anything, but I really love this subject.

I know there is not much proof or none at all to any of the common theories, so that makes me feel more comfortable to rationalize my own little theory. I don't know, it probably is already a part of some other theory, but here goes:

Based on how everything seems to repeat itself in nature - on different structural scales we see similarities of the basic links and arrangements. _Now this should sound really silly to anyone who knows anything about biology/astrophysics: _so from looking at the structure of an atom to a solar system / planets with moons, then looking at galaxies supposedly spinning around black holes - makes me want to draw a parallel from that. And another thing which _really_ freaked me out: I was watching some documentary about the universe and they were showing what I think was thermal maps of the universe, showing how it's mostly uniform because of the inflation thing. Anyway. Then they showed another map similar to the previous one which showed the clusters of galaxies, and **** me but it looked way too similar to neuron cells in the brain and all. I had a week of going crazy after I saw that. Below: the best I could find to show the 'galaxy cluster map' .









So my little theory is very philosophical and not at all scientific, but it would say that everything is similar at a different level or scale, so there can really be no end to this 'russian doll' effect and I wouldn't think our universe is the end.

And in general *I* shouldn't even be thinking about it because now I'm asking myself what are those different scales, and are they determined by space? time? whatever else? if there is no end could it be like the snake eating it's own tail? 
_
Now you know where I went with the whole universe/brain thing but I'm definitely not going to write about it, not in *science *forum at least! _


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## Kon

roughh said:


> So my little theory is very philosophical and not at all scientific, but it would say that everything is similar at a different level or scale, so there can really be no end to this 'russian doll' effect and I wouldn't think our universe is the end.


I believe David Bohm (of the "Holographic Universe" and "Implicate order" fame) suggests such a scheme and for the possibility that compact dimensions lead to a potentially never ending series of "Russian Dolls" where entire Universes may be packed inside a single sub-atomic particle, etc.. But I'm not sure because I can't understand much about his philosophy but his perspective on QM is 1 of the major interpretations of QM:

http://plato.stanford.edu/entries/qm-bohm/


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## fatelogic

EDIT:



> I know there is not much proof or none at all to any of the common theories, so that makes me feel more comfortable to rationalize my own little theory.


 most theories don't need much proof to become theories, but they need at least some type of "proof". For example, the super massive black hole in the center of our milky way theory just came to be just because they saw a tail in the center of our milky way (or another galaxy) with a telescope. So tail equalled "something must be sucking in our galaxy really fast." They claim it is a black hole further by this evidence back in 2008 http://news.bbc.co.uk/2/hi/science/nature/7774287.stm If you ask me, that is comparable to the loch ness monster sighting.

Though there are other theories that are closer to the truth. e.g. electric current flow (electricity).



> I was watching some documentary about the universe and they were showing what I think was thermal maps of the universe, showing how it's mostly uniform because of the inflation thing. Anyway. Then they showed another map similar to the previous one which showed the clusters of galaxies, and **** me but it looked way too similar to neuron cells in the brain and all. I had a week of going crazy after I saw that.


 Galaxies clustering is another theory. They don't know if it is correct or not. But that made up picture... it does kind of look how they put neuron communication on paper.



> So my little theory is very philosophical and not at all scientific, but it would say that everything is similar at a different level or scale, so there can really be no end to this 'russian doll' effect and I wouldn't think our universe is the end.


That's where string theory (and that theory also has sub-theories if I'm not mistaken) comes in to play I believe- that there are many universes (big bangs) out there young and old.


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## transhuman

Humans contemplating the ultimate nature of the universe is kind of like ants trying to contemplate quantum mechanics. If we consider that only one-billionth of the electromagnetic spectrum is visible to humans, and when we consider that we can barely explain only 4% of the observable universe (the rest of it being dark matter and dark energy), it is clear that the human brain is not sufficiently equipped to accurately assess ultimate reality. With this in mind, based on our best understanding of the world around us, the multiverse is likely true and infinite and eternal in nature.


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## hoddesdon

transhuman said:


> Humans contemplating the ultimate nature of the universe is kind of like ants trying to contemplate quantum mechanics. If we consider that only one-billionth of the electromagnetic spectrum is visible to humans, and when we consider that we can barely explain only 4% of the observable universe (the rest of it being dark matter and dark energy), it is clear that the human brain is not sufficiently equipped to accurately assess ultimate reality. With this in mind, based on our best understanding of the world around us, the multiverse is likely true and infinite and eternal in nature.


The "multiverse" does not exist. There is absolutely no scientific evidence for it. I thought science insisted on evidence, and drank at the well of facts.

As you say, humans can not comprehend the complexities of the universe, yet it is purely the product of chance (?) What you have said contradicts that idea.

The "multiverse" is just an excuse not to acknowledge that the universe is so extraordinary, and so fine-tuned for life, that it can not be an accident (hint: God created the universe). The only way it can be an accident is if there is an astronomical number of other universes, all of which are dysfunctional, so that the laws of probability allow a single one like this one to exist by chance.


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## Kon

hoddesdon said:


> The "multiverse" is just an excuse not to acknowledge that the universe is so extraordinary, and so fine-tuned for life, that it can not be an accident (hint: God created the universe). The only way it can be an accident is if there is an astronomical number of other universes, all of which are dysfunctional, so that the laws of probability allow a single one like this one to exist by chance.


Actually many biologists question the need for a multiverse to explain life as they cite the vast physical, fossil, genetic, and other biological evidence consistent with life having been fine-tuned through natural selection to adapt to the physical and geophysical environment in which life exists. *Life, they argue, was adapted to physics, and not vice versa; *"the universe is not fine-tuned to life; life is fine-tuned to the universe."


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## hoddesdon

Kon said:


> Actually many biologists question the need for a multiverse to explain life as they cite the vast physical, fossil, genetic, and other biological evidence consistent with life having been fine-tuned through natural selection to adapt to the physical and geophysical environment in which life exists. *Life, they argue, was adapted to physics, and not vice versa; "*the universe is not fine-tuned to life; life is fine-tuned to the universe"


But there are still minimum requirements for life e.g. an energy source. That is the sun. Another is a planet. If there were an undifferentiated collection of dust sprinkled uniformly throughout the universe, and it had not formed stars and planets, then life could not exist. So there is at least some fine-tuning for life by the universe, at least.


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## ugh1979

fatelogic said:


> ^ok you believe you know .. tell me within 5 minutes,
> 
> why do galaxies cluster?


On the most fundamental level, it's believed to be due to quantum fluctuations.



> and why do galaxies don't fall apart since the gravitational pull is too weak to keep them together?


It's believed dark matter provides the additional gravity to hold them together.


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## ugh1979

hoddesdon said:


> The "multiverse" does not exist. There is absolutely no scientific evidence for it. I thought science insisted on evidence, and drank at the well of facts.


To the contrary, the majority of modern physicists believe there could well be a multiverse. Many of our best theories indicate it. You can't say that it doesn't exist any more than someone saying it does exist.



> The "multiverse" is just an excuse not to acknowledge that the universe is so extraordinary, and so fine-tuned for life, that it can not be an accident (hint: God created the universe). The only way it can be an accident is if there is an astronomical number of other universes, all of which are dysfunctional, so that the laws of probability allow a single one like this one to exist by chance.


Wrong.

There is evidence now that suggests the universe maybe isn't as fine tuned for life as it first seemed. In fact, we can't say for sure what the knock on effect of changing certain properties would have in the universe being able to sustain life. Of course there are some conditions where life as we know it couldn't exist, and there are probably a lot of universes where this is the case, but by chance there are probably lots where the physics is suitable for life to form.

It's illogical to say all other universes would be dysfunctional and just our one could harbour life.  To the contrary, others must if ours does as they would have just as much chance.


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## hoddesdon

ugh1979 said:


> There is evidence now that suggests the universe maybe isn't as fine tuned for life as it first seemed......
> 
> It's illogical to say all other universes would be dysfunctional and just our one could harbour life. To the contrary, others must if ours does as they would have just as much chance.


The universe is definitely fine-tuned for life. If water were not the only thing weighing less as a solid than as a liquid, life would be impossible. Time is the only property of physics which can not have a negative value. Were it not so, there would be chaos, as the various films about time-travel demonstrate. There is a multitude of similar facts. Is it just a coincidence? What is the evidence that it is not as fine-tuned as it first seemed. I have noticed that when these statements are thrown around the evidence is not specified.

It is inherent in the theory of the "multiverse" that the other universes must be dysfunctional. The whole thing is a circular argument: the fine-tuning of the universe suggests deliberate creation; scientists refuse to accept it; therefore an alternate explanation is dreamt up. To say there is no deliberate creation means that an extremely improbable event has occurred, so dream up an astronomical number of other universes - for which there is no evidence - to make the one in a trillion-to-the-power-of-a-trillion shot possible. That only works if all the other universes are dysfunctional.


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## ugh1979

hoddesdon said:


> The universe is definitely fine-tuned for life. If water were not the only thing weighing less as a solid than as a liquid, life would be impossible. Time is the only property of physics which can not have a negative value. Were it not so, there would be chaos, as the various films about time-travel demonstrate. There is a multitude of similar facts. Is it just a coincidence? What is the evidence that it is not as fine-tuned as it first seemed. I have noticed that when these statements are thrown around the evidence is not specified.


Here's one source of many I've read over the years:

"If the force of gravity were a few per cent weaker, it would not squeeze and heat the centre of the sun enough to ignite the nuclear reactions that generate the sunlight necessary for life on Earth. But if it were a few per cent stronger, the temperature of the solar core would have been boosted so much the sun would have burned out in less than a billion years - not enough time for the evolution of complex life like us.

In recent years many such examples of how the laws of physics have been "fine-tuned" for us to be here have been reported. Some religious people claim these "cosmic coincidences" are evidence of a grand design by a Supreme Being. In The Fallacy of Fine-tuning, physicist Victor Stenger makes a devastating demolition of such arguments.

A general mistake made in search of fine-tuning, he points out, is to vary just one physical parameter while keeping all the others constant. Yet a "theory of everything" - which alas we do not yet have - is bound to reveal intimate links between physical parameters. A change in one may be compensated by a change in another, says Stenger.

In addition to general mistakes, Stenger deals with specifics. For instance, British astronomer Fred Hoyle discovered that vital heavy elements can be built inside stars only because a carbon-12 nucleus can be made from the fusion of three helium nuclei. For the reaction to proceed, carbon-12 must have an energy level equal to the combined energy of the three helium nuclei, at the typical temperature inside a red giant. This has been touted as an example of fine-tuning. But, as Stenger points out, in 1989, astrophysicist Mario Livio showed that the carbon-12 energy level could actually have been significantly different and still resulted in a universe with the heavy elements needed for life.

The most striking example of fine-tuning appears to be the dark energy - or energy of the vacuum - that is speeding up the expansion of the universe. Calculations show it to be 10(120) bigger than quantum theory predicts. But Stenger stresses that this prediction is made in the absence of a quantum theory of gravity, when gravity is known to orchestrate the universe.

Even if some parameters turn out to be fine-tuned, Stenger argues this could be explained if ours is just one universe in a "multiverse" - an infinite number of universes, each with different physical parameters. We would then have ended up in the one where the laws of physics are fine-tuned to life because, well, how could we not have?

Religious people say that, by invoking a multiverse, physicists are going to extraordinary lengths to avoid God. But physicists have to go where the data lead them. And, currently, there are strong hints from string theory, the standard picture of cosmology and fine-tuning itself to suggest that the universe we can see with our biggest telescopes is only a small part of all that is there."



> It is inherent in the theory of the "multiverse" that the other universes must be dysfunctional. The whole thing is a circular argument: the fine-tuning of the universe suggests deliberate creation; scientists refuse to accept it; therefore an alternate explanation is dreamt up. To say there is no deliberate creation means that an extremely improbable event has occurred, so dream up an astronomical number of other universes - for which there is no evidence - to make the one in a trillion-to-the-power-of-a-trillion shot possible. That only works if all the other universes are dysfunctional.


I don't see how it's that improbable and is in no way inherent of a multiverse that all other universes must be dysfunctional. That makes no sense at all. If all other universe were dysfunctional so would ours, as ours has no reason to be the one exception. In fact that sounds like typical theist arrogance.

Also, you are confining your argument to life as we know it. Life in other universes could be vastly different to life as we know.

You also seem to be ignoring all the other good theories that indicate a multiverse. It's certainly not confined to the argument surrounding the apparent fine-tuning of this universe to life. (Look in to quantum physics and theories such as string theory for other indications of multiverses)

As I say, the majority of physicists now believe in a multiverse, and they are a lot better educated and qualified to say so than you!


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## Kon

I don't understand this obsession and self-centerdness with human life. In many ways I don't think the evolution of life/human life is that much more astounding than the evolution of of helium from hydrogen. It's kind of built into the laws of physics. What is astounding to me is the laws themselves that give rise to the evolution of the whole thing; that is, why any laws or why something exists in the first place. It seems very difficult to imagine something as having no cause. And yet, if you assume cause, it seems to lead to an infinite regress because you can always ask previous cause. It seems one is almost driven to accept that the universe must in some ways be eternal. Or time/causality as we understand it, is an illusion.


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## fatelogic

I see that it took you more than 5 minutes to answer this...



> On the most fundamental level, it's believed to be due to quantum fluctuations.


 There is only one reason that idea came to be and quantum fluctuations is not it.



> It's believed dark matter provides the additional gravity to hold them together.


 dark matter is nothing though.... it is not even matter. From wiki - *Matter* is a general term for the substance of which all physical objects consist.[1][2] Typically, matter includes atoms and other particles which have mass. A common way of defining _matter_ is as anything that has mass and occupies volume.[3]

EDIT:

I went to go read on some news when I logged off and stumbled upon this article http://arstechnica.com/science/news...see-it-now-you-dont-nature-of-dark-matter.ars They are trying but dark matter is still a mystery.


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## fatelogic

> There is evidence now that suggests the universe maybe isn't as fine tuned for life as it first seemed. In fact, we can't say for sure what the knock on effect of changing certain properties would have in the universe being able to sustain life.


 huh!... I can bet a dollar that the "evidence" only exists withing some "theories" and out side those theories, that evidence dies.

There is "evidence" that our earth's "gravity" is caused by the magma in the core. But there is also evidence that gravity is not pulling us down but something else is. Only the mainstream ideas get the most attention though.

Now, just try to think about it... what is your point in trying to believe that "*the universe isn't as fine tuned for life*"? What is the purpose behind that logic? Specially since our planet and life was made in the universe from universe matter.

Any intelligent person can see that the universe is like dirt to a plant. So how is It not fined tuned for life? Do you have a better recipe?


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## ugh1979

fatelogic said:


> There is only one reason that idea came to be and quantum fluctuations is not it.


OK so if you think it isn't what is it then?



> dark matter is nothing though.... it is not even matter.


Regardless of what it is or isn't, it is believed to be responsible for making up the shortfall in gravity to hold galaxies together.

How can you disagree with me on the questions your asked me if you don't have any answers of your own to offer? :|


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## ugh1979

fatelogic said:


> huh!... I can bet a dollar that the "evidence" only exists withing some "theories" and out side those theories, that evidence dies.


Welcome to theoretical physics.



> There is "evidence" that our earth's "gravity" is caused by the magma in the core. But there is also evidence that gravity is not pulling us down but something else is. Only the mainstream ideas get the most attention though.


:lol Good luck with that.



> Now, just try to think about it... what is your point in trying to believe that "*the universe isn't as fine tuned for life*"? What is the purpose behind that logic? Specially since our planet and life was made in the universe from universe matter.
> 
> Any intelligent person can see that the universe is like dirt to a plant. So how is It not fined tuned for life? Do you have a better recipe?


The point is that life may actually be fine tuned to the universe, rather than the universe fine tuned for life. Life may well have simply adapted to the conditions of this universe, as it may well do in other universes with different conditions. This means that certain changes to the physics in our universe may not mean life couldn't exist, which nulls the idea that the universe is so fine tuned for life it couldn't be any different.


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## Cat Montgomery

I believe in the expanding and contracting (or what ever its called) theory. What that is, is that the universe always was. It continuously expands, until it reaches its maximum size, then is begins to contract. Then, everything in the universe comes to a single point, and starts expanding again, in a huge explosion (big bang). So yes, there is a "size" to the universe.


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## Cynical

I believe in the multiverse theory just because its logical and makes sense.


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## ugh1979

kunak said:


> I think its a fractal like the Mandelbrot personally. Seems to be that way.


Yeah I've always thought of the nature of the cosmos being fractal.


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## Pharoah

I dont know


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## 6OH2

I don't see how the universe can be infinite if it started at a point infinitely small (the big bang). Just knowing that the universe is expanding seems to imply that it cannot be infinite in size.


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## Kon

6OH2 said:


> I don't see how the universe can be infinite if it started at a point infinitely small (the big bang). Just knowing that the universe is expanding seems to imply that it cannot be infinite in size.


That's not accurate. Big bang doesn't imply that the universe is finite:

Look at the diagram and explanations here.

"In the view on the left, this same part of the Universe is shown by the green circle, but now the green circle is a tiny fraction of the 78 billion light year box, and the box is an infinitesimal fraction of the whole Universe. If we go to smaller and smaller times since the Big Bang, the green circle shrinks to a point, but the 78 billion light year box is always full, and it is always an infinitesimal fraction of the infinite Universe."

Big bang theory does not specify whether universe is finite or infinite.

http://www.astro.ucla.edu/~wright/infpoint.html


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## kev

Cat Montgomery said:


> I believe in the expanding and contracting (or what ever its called) theory. What that is, is that the universe always was. It continuously expands, until it reaches its maximum size, then is begins to contract. Then, everything in the universe comes to a single point, and starts expanding again, in a huge explosion (big bang). So yes, there is a "size" to the universe.


Ahh, interesting. I have read about that theory and found it very elegant.

I haven't read through all the replies but am glad to see so many people are interested.


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