3 ms·

I'm afraid none of these explanations work for me. All of these analogies have the same fatal flaw, regardless of what you try to use to describe how distance b

I'm afraid none of these explanations work for me. All of these analogies have the same fatal flaw, regardless of what you try to use to describe how distance between points expands you still have a material in a container. With a balloon, the container is the air around it. If you inflate a balloon, sure the two points you've drawn onto the balloon get further apart, but dammit the VOLUME of the balloon is increasing too. If space is like a balloon, what does it's "volume" consist of? When it expands (a balloon), it is displacing something (air), what does space displace as it expands? Now we're right back at the "fundamental misunderstanding of the space expansion theorem" again... So what about if I pose the same question in a different thought experiment. Go back to the origin, the big bang. Everything is in this super condensed super hot state (from wikipedia). Lets say you are this tiny rebellious particle and you decide you've had enough, you're not gonna wait around for this "inflation" event to occur that every one is all excited and talking about. You take off, at an infinite speed away from wherever you currently are. PBBU TRP (#) . So, if the Pre-Big Bang Universe is on the left, and the Theoretical Rebellious Particle is on the right, what is TRP in NOW?

natep 15y ago
Every one of these analogies are flawed in some way because they are just that, analogies, and the authors of them acknowledge that. You are meant to look at only the aspects of the situation that are analogous, and ignore the parts where the analogy breaks down, because no one is trying to claim that is actually how the universe works. To answer your question, your TRP cannot have ever existed, even in theory. There is no 'outside the universe' for the TRP to have gone, even at the time of the big bang. You seem to think that the big bang happened at a specific point, which is not true. The 'big bang' happened at every point, and never really 'bang'ed at all. Things are not moving away from each other so much as the distance between things is getting larger, which has a similar effect.
- giberson 15y ago
  Expanding on "There is no 'outside the universe'". Is the universe infinite in dimension? Is there such a path that a particle could take at infinite speed for an infinite time such that the distance between itself and a particle that had stayed in the same position is always increasing? Is there infinite matter in the universe? If no, is there a point at which this traveling particle will have left the "vicinity" of all matter, to never meet another particle again?
  - smeg 15y ago
    The problem is you are applying linear Earth-scale concepts of space to the whole Universe. In reality space (or space-time) is curved - as you approach the "edge" of the universe you actually are traversing a loop around a 4-dimensional hyper-sphere. The common analogy of an ant on the surface of a balloon is quite effective. As the balloon expands, the distance between points on the surface of the balloon certainly grow and they become further apart. The ant can measure this, see this, but for the life of him, no matter how far he walks, he cant find the "edge of the universe". Of course it is hard to visualise this analogy when projected into our 4-dimensional universe, but it's the best we've got.
    - natep 15y ago
      No, you do not 'loop around' the universe. It is flat, not a hyper-sphere. The 4th dimension of the universe is time, and not spatial.
  - natep 15y ago
    (Edit: I'm responding to each question in its own paragraph) What do you mean, 'infinite in dimension'? The universe has only 4 dimensions, 3 spatial, 1 in time. Your question barely makes sense to me. Why do you need to invoke infinite speeds and times? If 2 particles stay in the same place, and do not interact with each other (gravitationally, electromagnetically, etc) then the distance between those 2 particles would increase over time, due to the expansion of the universe. Yes, there is an infinite amount of matter in the universe [1] Maybe. If you pick a random direction and travel really fast for a really long time, the chances of you running into any other matter is extremely remote. [2] [1] http://www.reddit.com/r/askscience/comments/ewt9y/good_analogy_for_the_ends_of_the_universe/c1bn55h http://www.reddit.com/r/askscience/comments/ewt9y/good_analo... [2] http://www.youtube.com/watch?v=0fKBhvDjuy0 http://www.youtube.com/watch?v=0fKBhvDjuy0
    - giberson 15y ago
      What do you mean, 'infinite in dimension'? The universe has only 4 dimensions, 3 spatial, 1 in time. I'm was not asking how many dimensions the universe has. I was asking if the universe is infinitely tall, infinitely wide and infinitely long. Why do you need to invoke infinite speeds and times? Simply for matters of scale. I was trying to avoid considerations like "it's so big, it would take so long ...". If 2 particles stay in the same place [...] Actually, it's one particle that moves, and other is stationary, thus providing two points of reference for determining a displacement. Specifically the intention was to indicate a path through space such that you always are moving further from where you started and will never arrive back at your starting point (as opposed to the spherical theory of space such that you can only go half way around the sphere until you start getting closer to the point at which you started. If you pick a random direction and travel really fast for a really long time, the chances of you running into any other matter is extremely remote. I didn't mean physically collide with other matter, I simply meant to pass by it in the "vicinity". Similar to how traveling along a highway you pass by or through towns, you don't physically collide with them though. If matter in the universe was finite, then regardless of how sparse that matter is, there's an imaginary bounding box you could draw around all matter in the universe. A particle moving really fast for a long time would eventually end up outside of that bounding box. At which point its distance not just from the stationary particle at it's original, but all particles of matter would forever be increasing. However, if matter is in fact infinite, then such a scenario can not occur. Luckily, despite my questions barely making any sense, you've managed to provide in your reference [1] a comment that answers exactly my questions so thank you for that.

natep 15y ago

Every one of these analogies are flawed in some way because they are just that, analogies, and the authors of them acknowledge that. You are meant to look at only the aspects of the situation that are analogous, and ignore the parts where the analogy breaks down, because no one is trying to claim that is actually how the universe works. To answer your question, your TRP cannot have ever existed, even in theory. There is no 'outside the universe' for the TRP to have gone, even at the time of the big bang. You seem to think that the big bang happened at a specific point, which is not true. The 'big bang' happened at every point, and never really 'bang'ed at all. Things are not moving away from each other so much as the distance between things is getting larger, which has a similar effect.

giberson 15y ago
Expanding on "There is no 'outside the universe'". Is the universe infinite in dimension? Is there such a path that a particle could take at infinite speed for an infinite time such that the distance between itself and a particle that had stayed in the same position is always increasing? Is there infinite matter in the universe? If no, is there a point at which this traveling particle will have left the "vicinity" of all matter, to never meet another particle again?
- smeg 15y ago
  The problem is you are applying linear Earth-scale concepts of space to the whole Universe. In reality space (or space-time) is curved - as you approach the "edge" of the universe you actually are traversing a loop around a 4-dimensional hyper-sphere. The common analogy of an ant on the surface of a balloon is quite effective. As the balloon expands, the distance between points on the surface of the balloon certainly grow and they become further apart. The ant can measure this, see this, but for the life of him, no matter how far he walks, he cant find the "edge of the universe". Of course it is hard to visualise this analogy when projected into our 4-dimensional universe, but it's the best we've got.
  - natep 15y ago
    No, you do not 'loop around' the universe. It is flat, not a hyper-sphere. The 4th dimension of the universe is time, and not spatial.
- natep 15y ago
  (Edit: I'm responding to each question in its own paragraph) What do you mean, 'infinite in dimension'? The universe has only 4 dimensions, 3 spatial, 1 in time. Your question barely makes sense to me. Why do you need to invoke infinite speeds and times? If 2 particles stay in the same place, and do not interact with each other (gravitationally, electromagnetically, etc) then the distance between those 2 particles would increase over time, due to the expansion of the universe. Yes, there is an infinite amount of matter in the universe [1] Maybe. If you pick a random direction and travel really fast for a really long time, the chances of you running into any other matter is extremely remote. [2] [1] http://www.reddit.com/r/askscience/comments/ewt9y/good_analogy_for_the_ends_of_the_universe/c1bn55h http://www.reddit.com/r/askscience/comments/ewt9y/good_analo... [2] http://www.youtube.com/watch?v=0fKBhvDjuy0 http://www.youtube.com/watch?v=0fKBhvDjuy0
  - giberson 15y ago
    What do you mean, 'infinite in dimension'? The universe has only 4 dimensions, 3 spatial, 1 in time. I'm was not asking how many dimensions the universe has. I was asking if the universe is infinitely tall, infinitely wide and infinitely long. Why do you need to invoke infinite speeds and times? Simply for matters of scale. I was trying to avoid considerations like "it's so big, it would take so long ...". If 2 particles stay in the same place [...] Actually, it's one particle that moves, and other is stationary, thus providing two points of reference for determining a displacement. Specifically the intention was to indicate a path through space such that you always are moving further from where you started and will never arrive back at your starting point (as opposed to the spherical theory of space such that you can only go half way around the sphere until you start getting closer to the point at which you started. If you pick a random direction and travel really fast for a really long time, the chances of you running into any other matter is extremely remote. I didn't mean physically collide with other matter, I simply meant to pass by it in the "vicinity". Similar to how traveling along a highway you pass by or through towns, you don't physically collide with them though. If matter in the universe was finite, then regardless of how sparse that matter is, there's an imaginary bounding box you could draw around all matter in the universe. A particle moving really fast for a long time would eventually end up outside of that bounding box. At which point its distance not just from the stationary particle at it's original, but all particles of matter would forever be increasing. However, if matter is in fact infinite, then such a scenario can not occur. Luckily, despite my questions barely making any sense, you've managed to provide in your reference [1] a comment that answers exactly my questions so thank you for that.