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The edge of the universe

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    #32
    lasersquad
    Closed Accounts Posts: 58 ✭✭lasersquad


    Hi folks, 1st post...
    Capt'n Midnight wrote: »
    even vacuum can produce energy fluctuations and create new particles

    Yes, but if we allowed for super-perfect vacuum? A space that truly contains nothing and in which nothing happens?


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    #33
    Maximus Alexander
    Registered Users Posts: 13,080 ✭✭✭✭Maximus Alexander


    lasersquad wrote: »
    Hi folks, 1st post...



    Yes, but if we allowed for super-perfect vacuum? A space that truly contains nothing and in which nothing happens?

    Would it not be simpler to go with current theories suggesting that the universe has no edge, than to conjure up new mechanisms to explain this never-ending void, where the rules are different to those in the observable universe?


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    #34
    lasersquad
    Closed Accounts Posts: 58 ✭✭lasersquad


    Of course not. It`d be quite boring and unscientific. Besides these "current theories" were also "conjured" at some point.


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    #35
    Maximus Alexander
    Registered Users Posts: 13,080 ✭✭✭✭Maximus Alexander


    Yes but they were "conjured" on a basis of mathematics and observable evidence and work quite well to explain what we see.

    Suggesting that there is an unending void at the "edge" of the universe would require you to throw all of that away and start over. For no good reason, since there is nothing to suggest that such a void exists.

    If we were to just "allow" for this as you suggest, without a basis, that would actually be extremely unscientific.


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    #36
    lasersquad
    Closed Accounts Posts: 58 ✭✭lasersquad


    So, throwing ideas around and sometimes starting over from scratch is "unscientific"? That`s a good one ;)

    Current theories might work for observable universe - to a point. Apart from the obvious fact that by default our cute "void" is not observable, there are things like dark energy/matter - mysteries that are only being unraveled recently and are rather significant to the whole picture.

    Followed by other rather obvious things, like that from these many theories only one might be "right", some of them are based at least partially on speculation, folks at CERN have no problem talking about "new physics" in every other press release, etc, etc.

    But, if this is one of the forums where current science = religion (as in: can not be questioned) please say so - I`ll apologise for gatecrashing and disappear promptly.


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    #37
    Maximus Alexander
    Registered Users Posts: 13,080 ✭✭✭✭Maximus Alexander


    lasersquad wrote: »
    So, throwing ideas around and sometimes starting over from scratch is "unscientific"? That`s a good one ;)

    Current theories might work for observable universe - to a point. Apart from the obvious fact that by default our cute "void" is not observable, there are things like dark energy/matter - mysteries that are only being unraveled recently and are rather significant to the whole picture.

    Followed by other rather obvious things, like that from these many theories only one might be "right", some of them are based at least partially on speculation, folks at CERN have no problem talking about "new physics" in every other press release, etc, etc.

    But, if this is one of the forums where current science = religion (as in: can not be questioned) please say so - I`ll apologise for gatecrashing and disappear promptly.

    I'm sorry but the bolded part is one of those ludicrous things that gets bandied about a lot these days when someone has a random idea that flies in the face of rigorously tested theories.

    You seem to be reacting as though I have attacked you, when all I am doing is probing the basis for your hypothesis that the universe has an edge, beyond which there is an endless void governed by physics different from that which we observe.

    I could just as easily posit that the universe is contained within a giant teapot, sitting on someone's kitchen shelf, but that the walls of the teapot are outside of the observable universe, so we can't see them.

    Is your idea falsifiable? If so, how would we go about testing it? If we can't, then I would suggest that it is unscientific. Like religion.


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    #38
    himnextdoor
    Closed Accounts Posts: 1,042 ✭✭✭himnextdoor


    lasersquad wrote: »
    Hi folks, 1st post...



    Yes, but if we allowed for super-perfect vacuum? A space that truly contains nothing and in which nothing happens?

    Well, if we go with the big bang then it is easy to see how a medium containing all points trapped inside a medium containing no points might cause an energy differential that is enough to initiate a big bang.

    How would a pointless universe interact with points? Eternally I reckon.

    I sometimes imagine universal expansion in terms of pressurised space that is leaking away into a true void. As if space was a compressed gas contained in a slightly porous vessel. If gas were escaping through the wall of the container equally in all directions then the space inside the container would behave in a similar way to the observed Universe.

    I like this because it means two things; it provides a basis for defining an edge to the Universe and it means the Universe will continue to expand toward infinity forever.

    I might define the radius of the Universe as 'the distance travelled by the very furthest photon from the origin of the big bang'. Perhaps the photon is the only thing small enough to get through the porous wall? Perhaps the distance between photons at the edge of the Universe is related to its porosity?

    Which leads to us realising that the pressure inside the can will never be equal to the pressure outside and this has the interesting consequence that, in effect, the photons that define the edge of the Universe can be regarded as the wall of the can whose internal pressure is greater than the external pressure; infinity, the eternal movement of energy, constant change forever.

    In a way, the Universe is based on the relationship between 'inside' and 'outside' - the direction of expansion. Maybe photons have a life-span; if we viewed them as equivalent to pressurised cans on a much smaller scale but with identical characteristics to the Universe itself then when their internal pressure falls to almost equalise the external pressure, their momentum begins to approach zero; maybe that's what space is made of, cans that are almost empty. Perhaps the edge of the Universe is littered with the emptiest cans.

    And in the end, there can never be an equal distribution of energy in the Universe and that, I suspect, is the engine of change.

    Another interesting thing is that if you consider the eternal void as being experienced as the central point of the imperfect vacuum then the whole thing works in reverse; you would have a 'great attractor' at the centre of the Universe; a cosmic plughole where unimaginably vast amounts of energy are being dissipated. And again, infinity; there will always be big bang events at the centre.

    Additionally, one imperfect point in an otherwise perfect vacuum would have the same consequence; it's simply a matter of scale.

    How could gravity not exist?

    I think the idea of an outside and an inside actually helps to simplify the problems of the Universe.


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    #39
    Nabber
    Registered Users Posts: 2,855 ✭✭✭Nabber


    The edge of the universe is a paradox. An edge would imply you have something to expand into. But if you can expand into it then there is something not nothing. If there is something beyond the 'edge' of the universe then where is it's edge? (Here we go again:pac:)

    So if our universe is finite, then how do you avoid a paradoxical edge? Perhaps a tube shaped universe forming a ring?
    If our universe is infinite. Then there is no edge, center or big bang. The 'expansion' we see is not expansion, but the distance between two objects getting larger.

    How do you get your head around infinity and pure nothingness?


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    #40
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    himnextdoor wrote: »
    I think the idea of an outside and an inside actually helps to simplify the problems of the Universe.
    The object of science isn't just to simplify problems by making stuff up with no evidence (or going against evidence) in order to make the problems go away.


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    #41
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Capt'n Midnight wrote: »
    Nope

    even vacuum can produce energy fluctuations and create new particles

    As I understand it. The particles can be created as long as the vanish immediately. And the particles do not fill the vacuum. It's mostly empty.

    Is it possible that the vacuum just goes on forever? And the universe doesn't have an edge - unless you consider the universe to be only the mass of created at the time of the big bang.


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    #42
    himnextdoor
    Closed Accounts Posts: 1,042 ✭✭✭himnextdoor


    Cú Giobach wrote: »
    The object of science isn't just to simplify problems by making stuff up with no evidence (or going against evidence) in order to make the problems go away.

    You mean like renormalisation theory?

    I'm just brain-storming dude. I'm not looking for a Nobel prize.

    What 'evidence' did I go against?


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    #43
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    himnextdoor wrote: »
    You mean like renormalisation theory?

    I'm just brain-storming dude. I'm not looking for a Nobel prize.

    What 'evidence' did I go against?
    Need I remind you of this thread.


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    #44
    Andrew Flexing
    Registered Users Posts: 657 ✭✭✭Andrew Flexing


    My head hurts...

    my URBAN EXPLORATION YouTube channel: https://www.facebook.com/ASMRurbanexploration/



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    #45
    Helix
    Closed Accounts Posts: 17,661 ✭✭✭✭Helix


    lasersquad wrote: »
    Hi folks, 1st post...



    Yes, but if we allowed for super-perfect vacuum? A space that truly contains nothing and in which nothing happens?

    surely "something", which is what this super-perfect vacuum would be, can't contain "nothing". meaning that if a super-perfect vacuum existed outside the universe, it would therefore not exist?

    or is that just pedantry?


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    #46
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    luckyfrank wrote: »
    It's hard to believe that the universe is not infinite, i mean there is a place where the universe just stops and then there in nothing

    no matter no space no time, but surly if the universe is expanding it must be expanding into something that wasnt there before

    Ive read before that it's not the universe that's expanding just that the space within it is expanding if that makes sense

    Hypothetical question : If i was standing on the very edge of the universe with a tennis ball in my hand and threw that ball over the edge what would happen to the ball ?

    If the universe is closed (current evidence does not suggest this), the universe would have no edge, just as the surface of the earth has no edge. If you threw a tennis ball, it would eventually hit you on the back of the head.

    If the universe is flat, then it might very well be infinite.


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    #47
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Morbert wrote: »
    If the universe is closed (current evidence does not suggest this), the universe would have no edge, just as the surface of the earth has no edge. If you threw a tennis ball, it would eventually hit you on the back of the head.

    If the universe is flat, then it might very well be infinite.

    I don't know. Certain explanations, that could over simplified or completely wrong, of things like the Higgs field, make the claim that it came into existence just shortly after the big bang.


    If the universe is truly infinite - then that should allow for other big bangs, possibly hundreds of billions of light years away from our observable universe.

    I have heard our universe (our star system) described as a vacuum fluctuation - if it is, then there should be others. And if the true universe is infinite nothingness, then it could contain and infinite number of star systems that are also quantum fluctuations.

    I wonder is the vacuum dimensionless nothingness - that allows dimensions according to the rules of whatever vacuum fluctuation happens.


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    #48
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    krd wrote: »
    I don't know. Certain explanations, that could over simplified or completely wrong, of things like the Higgs field, make the claim that it came into existence just shortly after the big bang.


    If the universe is truly infinite - then that should allow for other big bangs, possibly hundreds of billions of light years away from our observable universe.

    I have heard our universe (our star system) described as a vacuum fluctuation - if it is, then there should be others. And if the true universe is infinite nothingness, then it could contain and infinite number of star systems that are also quantum fluctuations.

    I wonder is the vacuum dimensionless nothingness - that allows dimensions according to the rules of whatever vacuum fluctuation happens.

    The big bang was not a local event. Whether the universe is finite or infinite, the big bang "happened" everywhere.

    The Wavefunction of the Universe, a paper by Hawking and Hartle, describes a possible model of the universe as arising from "nothing" (a zero three-geometry), which might suggest a "foam" of emerging universes. That is the closest thing to "multiple big bangs" I can think of.


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    #49
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Morbert wrote: »
    The big bang was not a local event.

    We do not know that.
    Whether the universe is finite or infinite, the big bang "happened" everywhere.

    If you limit your frame of reference to the early universe, which is visible through the cosmic background radiation - clearly visible. Then the universe is finite.

    But there's nothing to conclude that space is not infinite nothingness.
    The Wavefunction of the Universe, a paper by Hawking and Hartle, describes a possible model of the universe as arising from "nothing" (a zero three-geometry), which might suggest a "foam" of emerging universes. That is the closest thing to "multiple big bangs" I can think of.

    Path integrals - when you have a hammer.


    I have an idea that the nothingness (I won't call it the vacuum) may have it's own uncertainty principle. Something that allows it to have an infinite number of dimensions but at the same time none. And something that allows it to expand at an infinite rate, and simultaneously contract at an infinite rate. Which sounds contradictory but it might be possible because it's not there. I've been thinking about this. If those two principles are correct, then it might be possible for the nothingness to have an infinite number of universes like our own - and universes with completely different rules and dimensions. But because of a strange kind of relativity - something that allows contradictory infinities - those universes would seem dimensionless to the nothingness.

    If the nothingness is expanding an an infinite rate, then the universes are shrinking relative to it at an infinite rate. If the nothingness is shrinking at an infinite rate, then a Doppler like effect makes the universes dimensionless. There wouldn't be a foam, the empty space would always appear completely empty. Even if you could escape one of the universes you wouldn't notice any difference - all your rules and dimensions are allowed. Your chances of seeing or entering one of the other universes would be infinitely small. And I think, if you could enter one, your rules and dimensions would be preserved but you may be forbidden from viewing or experiencing the dimensions and rules of that universe.

    You don't need Hawking's idea of a universe bubbling up and tunnelling its' way to a bigger space. It just doesn't need to.

    If the same kind of thing is happening in the vacuums in our universe, you can forget about using anything like Planck's constant - or any of our constants to estimate what might be there. You're not going to see a foam either - the chances of seeing anything may be infinitely small, and we may have nothing in our dimensions that can interact with the dimensions of those things.


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    #50
    mooliki
    Registered Users Posts: 62 ✭✭mooliki


    krd wrote: »
    Something that allows it to have an infinite number of dimensions but at the same time none. And something that allows it to expand at an infinite rate, and simultaneously contract at an infinite rate. Which sounds contradictory but it might be possible because it's not there.

    Surely that's just philosophical meandering over the concept of "nothingness". No different from saying there's a cat sitting beside me that doesn't exist, that's both infinitely big and infinitely small, which is possible because it doesn't exist.


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    #51
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    mooliki wrote: »
    Surely that's just philosophical meandering over the concept of "nothingness". No different from saying there's a cat sitting beside me that doesn't exist, that's both infinitely big and infinitely small, which is possible because it doesn't exist.

    No, it isn't a philosophical meandering.

    You're in the same frame of reference as the cat. In your frame of reference the cat always remains the same size.

    And you've got the idea wrong - the cat can never be infinitely big.

    If the nothingness is contracting at an infinite rate in all directions - A Doppler like effect shrinks the cat to dimensionlessness. If the space is expanding, the cat is shrinking relative to the nothingness.

    The effect is, to the outside space, the cat's universe always appears dimensionless or of indeterminate dimensions. Within the cat's universe all kinds of dimensions and rules are allowed.

    The idea is not too different from the idea of quantum foam - but in my version, there is no foam. Recent results from Fermi Lab's Gamma ray telescope have shown the foam not to be there - or it wasn't detected. My idea is that all the stuff is still there, but the space will always appear empty.


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    #52
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    krd wrote: »
    We do not know that.

    Yes we do.
    If you limit your frame of reference to the early universe, which is visible through the cosmic background radiation - clearly visible. Then the universe is finite.

    But there's nothing to conclude that space is not infinite nothingness.



    Path integrals - when you have a hammer.


    I have an idea that the nothingness (I won't call it the vacuum) may have it's own uncertainty principle. Something that allows it to have an infinite number of dimensions but at the same time none. And something that allows it to expand at an infinite rate, and simultaneously contract at an infinite rate. Which sounds contradictory but it might be possible because it's not there. I've been thinking about this. If those two principles are correct, then it might be possible for the nothingness to have an infinite number of universes like our own - and universes with completely different rules and dimensions. But because of a strange kind of relativity - something that allows contradictory infinities - those universes would seem dimensionless to the nothingness.

    If the nothingness is expanding an an infinite rate, then the universes are shrinking relative to it at an infinite rate. If the nothingness is shrinking at an infinite rate, then a Doppler like effect makes the universes dimensionless. There wouldn't be a foam, the empty space would always appear completely empty. Even if you could escape one of the universes you wouldn't notice any difference - all your rules and dimensions are allowed. Your chances of seeing or entering one of the other universes would be infinitely small. And I think, if you could enter one, your rules and dimensions would be preserved but you may be forbidden from viewing or experiencing the dimensions and rules of that universe.

    You don't need Hawking's idea of a universe bubbling up and tunnelling its' way to a bigger space. It just doesn't need to.

    If the same kind of thing is happening in the vacuums in our universe, you can forget about using anything like Planck's constant - or any of our constants to estimate what might be there. You're not going to see a foam either - the chances of seeing anything may be infinitely small, and we may have nothing in our dimensions that can interact with the dimensions of those things.

    This is a hodge-podge.


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    #53
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Morbert wrote: »
    Yes we do.

    How?

    Do you have to start with the axiom, that before the big bang there was no space or time. Something like a religious creation myth.
    This is a hodge-podge.

    It's the popular science section, so I'm allowed do a Hodge Podge.


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    #54
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    krd wrote: »
    How?

    Do you have to start with the axiom, that before the big bang there was no space or time. Something like a religious creation myth.

    "Before the big bang" is already a problematic statement. Before the big bang is currently as well-defined as "north of the north pole". Instead, we say that the big bang is a topological phenomenon of spacetime, rather than a local event in spacetime.


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    #55
    mooliki
    Registered Users Posts: 62 ✭✭mooliki


    krd wrote: »
    No, it isn't a philosophical meandering.

    You're in the same frame of reference as the cat. In your frame of reference the cat always remains the same size.

    And you've got the idea wrong - the cat can never be infinitely big.

    Of course it can never be infinitely big, it doesn't exist. I wasn't actually trying to suggest some sort of cat analogy, simply trying to point out how devoid of scientific reasoning that kind of statement is. Obviously I failed. Carry on.


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    #56
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    mooliki wrote: »
    Of course it can never be infinitely big, it doesn't exist. I wasn't actually trying to suggest some sort of cat analogy, simply trying to point out how devoid of scientific reasoning that kind of statement is.


    What's wrong with the cat analogy? I could have said the cat was neither infinitely big nor infinitely small but in a superposition of states.

    What's unscientific about cats?


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    #57
    Justin1982
    Closed Accounts Posts: 328 ✭✭Justin1982


    Damn funny thread.

    Shape of the universe and the supposed "edge" of the universe are difficult things to get ones head around.

    Noone so far has given a correct description of the shape of the universe that General Relativity and experiment so far seems to indicate.

    Incorrect Version that permeates popular science:
    Universe exploded from a singular point and expanded out from that point at the speed of light and the edge of the universe is now ~14 billion light years away from us here on earth.........This is false!

    Correct Version:
    When the universe came into existence via the Big Bang theory (still not 100% proven), the universe was infinite. Its the space between each point in universe that has been expanding the last ~14 billion years.
    There is no real edge to the universe. The "edge" is basically due to a limit of our knowledge of the infinite universe. From any point in the universe, the farthest you can see is as far as light has already travelled since the big bang. But as time roles forward, so does the edge. As in we are receiving more and more light from further and further away. You can never actually reach the edge of the universe. Closest we can get to the edge of the universe (even if we travelled close to the speed of light) is ~14 Billion light years away from it.
    So for example there is probably some galaxies forming 20 billion light years away from us right now. But we cant see them now as the universe has only been around for 14 billion years. But if we wait around on our planet earth for the next 6 billion years, then our universe will eventually be 14 billion years old and the light from the 20 billion year old galaxy will then finally reach us and we can see it.
    This is all presuming that the universe is flat. Experiment seems to indicate that universe is flat so far.
    I read something something about the universe having to be flat theoretically as if it wasnt perfectly flat now then back when the universe was less than a second old then it wouldnt have been able to expand to form as we see it. As in if it is non flat now then it would be non flat to the same extent when the universe came into being. This would result in the universe expanding much too rapidly or collapsing straight away.
    Inflation adds more to the story but I wont confuse you.

    Want to understand then read Simon Singhs book "Big Bang". Best explanation of universe I've come across.


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    #58
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Justin1982 wrote: »
    Damn funny thread.

    Shape of the universe and the supposed "edge" of the universe are difficult things to get ones head around.

    It depends on what you think the universe is.

    A good book. Lawrence Krauss A Universe from Nothing: Why There Is Something Rather than Nothing. Though I have to give it a better read - I don't own a copy.

    Before Lemaître and Hubble, the milky way was considered to be the universe. Even Einstein said something to Lemaître along the lines of "Your math is correct, but your physics is abominable."

    The idea of the steady state universe didn't die until Penzias and Wilson finally put a nail through it in 1964.

    Krauss's thesis, which I believe is the conventionally accepted one at this point in time, is that our universe, all the stellar material from the big bang, was formed by a quantum fluctuation of empty space. Krauss says in his book, that space could be filled with universes like our own.

    So if the universe is something where something can happen - then the entire universe is endless. And it's mostly endless nothingness.

    Incorrect Version that permeates popular science:
    Universe exploded from a singular point and expanded out from that point at the speed of light and the edge of the universe is now ~14 billion light years away from us here on earth.........This is false!

    You know there are several Yellow Submarine type explanations of the shape of the Universe. One, that I think is attributed to Einstein, is that if you walk any direction in the Universe you'll eventually come back to the same point - I don't know whether that's due to gravity bending space, and looping you back to where you started or if it's like Nietzsche eternal return. Other definitions I've heard, material can travel in whatever direction it's travelling in and never come back to the same point.

    A thing about popular science writing, is you're going to see ideas that are known to be wrong for a long time - and you'll see them especially garbled. Like writings on black holes. The most common misconception you'll see written about black holes, is that if you were approaching one, you wouldn't see it. But according to Einstein you'll see gravitational lensing - space being bent around the hole - and according to Hawking, you'll see a lot of light. A giant spinning black hole would probably be the most spectacular sight in the universe. Centre astral objects we can see, appear to be that.

    In popular writing you'll see stuff like, as you approach a black hole you wouldn't see anything, and then you'll get turned into spaghetti, but you won't notice this as you'll be frozen infinitely in time. Or you'll see something like, a black hole is an infinitely tiny point in space with no radius.

    Black holes are wonderfully mind bending. Like Hawking's photons. Can they be entangled if one is behind the black hole horizon and the other isn't. What about superposition and black holes.


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