The edge of space

Discussion in 'Physics' started by amilton542, Nov 1, 2011.

  1. amilton542

    Thread Starter Active Member

    Nov 13, 2010
    494
    64
    The edge of space is something I always think about. We may define space as infinite. When we "rewind" time everything accumulates to a single point that exploded. If the "big-bang" is accelerating as a concentric sphere faster than the speed of light; then there must be a boundary to space, although it is defined as infinity?
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Maybe, maybe not. There are many theories about this, and they are also changing quite fast.

    When I was younger I would contemplate about it and try to examine and understand the rough edges around those theories.

    After a point though you see that even scientists disagree and review their positions about this topic and you realize that it's not very fruitful to dig around unfinished research ground. It's not about a well established subject, like electricity or gravitational pull; this is still very new ground.

    So for now thinking that the space is unthinkably large and currently expanding is enough for me.
     
  3. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
    764
    I also wonder if there is kind of a "North" or point of reference. Call it "center" if you like.

    If I drop you there in outer space could you say where you are with reference to what?

    As a seaman, so used to refer our position to North, that is a somewhat unsettling feeling for me.

    Once, years ago, I asked in one of those sites from Nasa, a question related to that. The engineer that answered said that at that moment the system was keeping track of your position wrt to Earth or know bodies.
     
  4. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    who rewound time to verify that everything started at a single point?

    Who verified that the universe is expanding faster than the speed of light? Seems an impossible thing to observe, since observation is limited to the speed of light. That, and nobody has ever seen the edge of space to verify it is expanding at all.

    If the universe is expanding, what is it expanding into? nothingness? how big is the nothingness? are there other universes in the nothingness? What happens if 2 expaning universes expand into eachother? is the nothingness expanding? are there other nothingnesses? These are all question which I don't think will ever be answered, and even if they could be answered, I don't think we would understand the answer.

    Reminds of the movie Men In Black; a dog had a universe hanging from his collar the size of a marble, full of galaxies with planets and creatures on planets. at the end of the movie, the camera zooms out from earth, through the galaxy, through the universe, and our universe was inside a marble on some other planet in a bigger universe. That sounds absolutely crazy, and the stuff of fiction movies, but so does the reality of the universe (to me anyways).

    I feel comfortable in my assumption that the universe is not expanding, and that it is infinite.
     
    justtrying and shortbus like this.
  5. PatM

    Active Member

    Dec 31, 2010
    81
    72
    If space is expanding, in every direction from the big bang, is there one spot in the center that is not moving/expanding ?
    Always wondered about that.
     
  6. amilton542

    Thread Starter Active Member

    Nov 13, 2010
    494
    64
    We know the universe is expanding because of the Doppler effect for electromagnetic waves which are an observational fact.

    Lets say the universe is not expanding faster than light. When the first star was born its light afer x amount of years will catch up with the expansion. Then what?

    Do I believe in a parallel universe? I'm not sure.
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    nothing? why would something happen?

    EDIT: Wait! you tricked me. I said I think the universe is infinite; meaning it doesn't have edges
     
    Last edited: Nov 2, 2011
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,015
    1,531
    A thing that bothers me about 'the big bang' and the universe is the so called "star nurseries". If there was a big bang, how do they justify star nurseries? If stars are born in these nurseries, how are they then distributed through out the rest of the universe? ..... Star storks?
     
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    From my perspective, the only reason to theorize that our universe began at a certain place and time and is expanding outwards is because we are not comfortable with accepting the idea of infinity, as it applies to time and to space. whether you look to science, science fiction, science theory, or religion to explain our existence & universe, at some point you have to accept the fact that there is such thing as infinity. Whether you choose to believe that our universe is infinite, or the area outside of it is infinite, one of the two has to be infinite. And whether or not you choose to believe that our universe has existed for infinity, or if you choose to believe that it began at a certain time, the time before it began was infinite. So as I said, I theorize that our universe has always existed and that it is infinite, because that theory leaves the least questions unanswered in my mind. I just push the "I believe button" because I still cannot fathom infinity; it seems impossible to me, but it must be possible. We as humans like to define things in finite ways.
     
  10. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
    764
    I am affraid that we cannot do otherwise, being finite ourselves. Our mind is at our level. Trying to understand the Ultimate Cause is beyond us, no matter what.

    I am convinced that wen we pass away ligth is switched off for us, forever.
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    To use Start Trek jargon that is a "sensor anomaly". ;)

    If there was a single big bang event, with release of energy pushing every bit of matter in the universe out, it would be like a shock wave you see on TV slow motion explosions etc, there would now be a massive void in the middle at ground zero. Our best telescopes cannot find any evidence of that void, so logically then it must be too far away.

    But here's the thing, if ground zero is that far away, then simple geometry dictates that all the mass near us (everything our telescopes CAN see) will be moving in roughly the same direction, including us! So our sensors would show everything not moving away much at all...

    My theory is that the whole universe ROILS. Or "The little bang theory" I call it. Bangs are a localised deal probably the size of galaxies. Galaxies spin and collapse in on themselves, then eventually burst back out. And in the universe it will be filled with a roughly uniform distribution of these roiling galaxies. This makes sense as given a long enough time all the matter and energy in the universe would be roughly evenly distributed, so any "bang" cycles would be small and be local. If my theory is correct then there would be galaxies in various states of their local bang cycle; as galaxies, nebulas, etc always visible. Everywhere.

    By common sense something can only exist forever in one of two conditions, either unchanging, or in a continuous cycle. A single big bang theory would have to comply with the second, as a cyclic repeating event. But, given enough release of energy to cause all the matter in the universe to start expanding outward, what is the thing/force that will halt the inertial movement of all this mass in space and reverse it to cause the contraction?
    It cannot logically satisfy a continual big bang cycle. And a one-time only big bang does not make sense either. What was the matter doing at the centre of the universe before the bang? How did it get there? Whay was it all in one spot in such an unstable fashion?

    I watch a lot of science channel documentaries on astro stuff and there are some real smart people spouting some real dumb theories... The only thing that makes sense is that the universe is stable, reasonably uniformly distributed, and subject to local cyclic phenomena (ie my "little bang theory") which would leave the universe as far as we can see filled with galaxies in various states of their own local cycle. And this silly "all the distant stuff is expanding away from us" concept should be logically dismissed as a sensor error caused by some facet of physics we may not understand fully yet.

    I don't buy it for one second that the universe extends infinitely far in all directions! It's more logical to assume that the universe is VERY big but curved, so if you go far enough you eventually get back to where you started. If that is the case, it may well explain something of that sensor anomaly where light from very far things seems to be experiencing something that looks like a doppler effect to our simple instruments.
     
    Last edited: Nov 3, 2011
  12. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    why not?

    Why?

    I consider both theories equally illogical, but I'm biased towards my own.
     
  13. amilton542

    Thread Starter Active Member

    Nov 13, 2010
    494
    64
    My theory is a door and corridor system:

    • If you walk through a door, do you step out through another and up where you were?
    • If you walk through a door, do you end up in an identical corridor?
    • If you zoom out, is it a maze of identical corridors suggesting symmetry?
    • If you number the doors can you give yourself a reference position?
    • If there is a wall behind one of the doors, does it violate the symmetry?
    • .........Up to the nth "If".
     
    Last edited: Nov 3, 2011
  14. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Many of the questions here do have answers, and ones that many can understand. Two hints if you want to research this. Non-euclidean geometry is believed to be the correct geometry for the universe, if you stick to euclidean you are lost. General Relativity is the best accepted theory for the universe which is dominated by gravity. It uses Riemann geometry, a differential geometry. Now often taught in undergraduate courses.

    A few notes based on current theory:

    * All points are the center of the universe, there is no special point.
    * The universe is finite, but unbounded.
    * The universe is indeed expanding and that expansion is changing over time.
    * GR is not consistent with quantum mechanics, this needs to be fixed.
    * There is a lot of room for improved understanding of this subject ( whose name is cosmology ).
     
    BillO likes this.
  15. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I've always favored the theory we are on the surface of a multidimensional balloon. Go far enough in any direction and you end up right back where you started.

    As for the argument of the universe not being infinite, it is simple enough. There appears to be a beginning, there is a finite boundary right there, and the width (for lack of a better word) of the universe is a function of time.
     
    BillO likes this.
  16. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Your first point is more or less right on ( we can view the universe as a 3 dim manifold embedded in a high dimentional manifold, although the second manifold is not required ) The balloon has no boundry in the 3 d space instead you return to where you started, not infinite, not bounded.

    Your second point seems to introduce a boundary based on time, not space, I do not think that is what we are discussing, the universe is still the balloon, just going to 0 size. At size equals 0 the equations fail and there is much speculation about possible resolutions.
     
    BillO likes this.
  17. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    what evidence is there of a beginning?



    if we beleive that mass/matter and also energy cannot be created or destoryed, then where did all this stuff around us come from? It couldn't have just materialized out of nothing; if you think that the universe "began" at some point, then what was the matter that made it up? simplest explanantion is that there is infinite matter and it has always been here.
     
  18. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Where is this stuff coming from? AFAIK none of this has or can be proven, yet you are presenting it as fact.
     
  19. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    For one thing the expansion can be played in reverse, and has been, leading to the big bang theory (which in spite of all its critics has held up pretty well). This is pretty basic physics. They think they have gotten it down to a few milliseconds after the big bang, maybe a lot closer.

    Last I heard the big discussions are about what caused the big bang to begin with, not whether it happened or not.
     
  20. MvGulik

    Member

    Nov 3, 2011
    40
    9
    Probably not, given the current general views on the subject.

    Think of the expansion of space(3d) in a 2d way. If you inflate a spherical balloon. It surface is expanding, but there is no definite point of origin for this expansion (on the 2d surface of the balloon).

    + The balloon surface also has no boundaries. But it still has a limited, although growing ... while blowing, surface area. So its not infinite in size but you still can travel around its surface (in a straight line for the 2d world traveler) for a infinite distance.

    (I see I skipped other balloon example posts.)
     
    Last edited: Nov 3, 2011
Loading...