4 ms·

It's because the movement is ascribed to the expansion of space itself, not the individual galaxies. We don't have any reason to believe galaxies are moving in

It's because the movement is ascribed to the expansion of space itself, not the individual galaxies. We don't have any reason to believe galaxies are moving in random directions at random speeds (not at scales that explain the redshifts we call the expansion of the universe). In your explanation, I think we'd expect to see some very distant, very slow-moving galaxies moving toward us. And there may be some very fast-moving galaxies close to us that just started really far away. Objects would be entering our local universe from outside it, and that simply doesn't happen.

arcastroe 3y ago
> In your explanation, I think we'd expect to see some very distant, very slow-moving galaxies moving toward us Thank you, but I suppose I'm not really questioning the big bang piece. My question was mostly in regards to the continued acceleration piece. Feel free to disregard the "in random directions" part of my original post. I'm picturing more of an explosion in empty space. A firework or granade of sorts. Any individual dust/shard of the explosion still sees all other objects moving away from it and the rest of my question stands. But I suppose this would imply a "center" to the explosion, which I've also heard is not the case. Theres a few other comments offering more clarity to the acceleration piece. Thank you everyone!
- pdonis 3y ago
  > I'm picturing more of an explosion in empty space. No, that's not what the big bang is. > this would imply a "center" to the explosion, which I've also heard is not the case That's correct. The big bang does not work like anything ordinary that you are used to imagining. The math is straightforward and unambiguous, but there is no good ordinary language description that corresponds to the math.
  - alexb23 3y ago
    I find helpful this analogy of the space-time (4-dimension) expansion from the big bang: the surface (2D) of an expanding bubble. YMMV.
  - lp4vn 3y ago
    As I understand it, before the big bang the whole observable universe was contained in a small sphere and then it started to expand metrically. Is this interpretation correct? Another thing: suppose I point a laser beam to the space and by chance this laser beam never finds any kind of matter in its way, where is this laser going to? To an infinite void? Is it correct to say that stars radiate energy to the infinite then?
    - pigpang 3y ago
      It's just an interpretation. Your interpretation is similar to the Big Bang model of visible Universe expansion. If you can convince us that your model is better than other models, then we will use your model, but nobody can prove than a model is correct, unless we will find a hidden recorder somewhere which was turned on for few dozens of billion years. Photon will hit something, or will travel until it will be redshifted to obvilion, or will travel until end of the medium (photon is a wave, so it waves something).
      - denton-scratch 3y ago
        > (photon is a wave, so it waves something) That sounds suspiciously like postulating the 'ether'. Surely what a photon 'waves' is the electromagnetic field, which is not a medium, and which fills the whole of spacetime. There is no 'end of the medium'.
        pigpang 3y ago
        "Field" means 3d array of numbers. Spacetime means 4d array of numbers. You are talking about mathematical model of Universe, while I'm talking about physics. Mountain is not just an excitement in a height field. If photon is not waving something, then it's not a wave. Physicists prove that photon is a wave.
        michaelsbradley 3y ago
        > If photon is not waving something, then it's not a wave. No, you’ve simply hit the limits of needing/wanting to understand something in terms of something else similar or more familiar. Makes the same point on a related matter: https://youtu.be/Q1lL-hXO27Q https://youtu.be/Q1lL-hXO27Q

arcastroe 3y ago

> In your explanation, I think we'd expect to see some very distant, very slow-moving galaxies moving toward us Thank you, but I suppose I'm not really questioning the big bang piece. My question was mostly in regards to the continued acceleration piece. Feel free to disregard the "in random directions" part of my original post. I'm picturing more of an explosion in empty space. A firework or granade of sorts. Any individual dust/shard of the explosion still sees all other objects moving away from it and the rest of my question stands. But I suppose this would imply a "center" to the explosion, which I've also heard is not the case. Theres a few other comments offering more clarity to the acceleration piece. Thank you everyone!

pdonis 3y ago
> I'm picturing more of an explosion in empty space. No, that's not what the big bang is. > this would imply a "center" to the explosion, which I've also heard is not the case That's correct. The big bang does not work like anything ordinary that you are used to imagining. The math is straightforward and unambiguous, but there is no good ordinary language description that corresponds to the math.
- alexb23 3y ago
  I find helpful this analogy of the space-time (4-dimension) expansion from the big bang: the surface (2D) of an expanding bubble. YMMV.
- lp4vn 3y ago
  As I understand it, before the big bang the whole observable universe was contained in a small sphere and then it started to expand metrically. Is this interpretation correct? Another thing: suppose I point a laser beam to the space and by chance this laser beam never finds any kind of matter in its way, where is this laser going to? To an infinite void? Is it correct to say that stars radiate energy to the infinite then?
  - pigpang 3y ago
    It's just an interpretation. Your interpretation is similar to the Big Bang model of visible Universe expansion. If you can convince us that your model is better than other models, then we will use your model, but nobody can prove than a model is correct, unless we will find a hidden recorder somewhere which was turned on for few dozens of billion years. Photon will hit something, or will travel until it will be redshifted to obvilion, or will travel until end of the medium (photon is a wave, so it waves something).
    - denton-scratch 3y ago
      > (photon is a wave, so it waves something) That sounds suspiciously like postulating the 'ether'. Surely what a photon 'waves' is the electromagnetic field, which is not a medium, and which fills the whole of spacetime. There is no 'end of the medium'.
      - pigpang 3y ago
        "Field" means 3d array of numbers. Spacetime means 4d array of numbers. You are talking about mathematical model of Universe, while I'm talking about physics. Mountain is not just an excitement in a height field. If photon is not waving something, then it's not a wave. Physicists prove that photon is a wave.
        michaelsbradley 3y ago
        > If photon is not waving something, then it's not a wave. No, you’ve simply hit the limits of needing/wanting to understand something in terms of something else similar or more familiar. Makes the same point on a related matter: https://youtu.be/Q1lL-hXO27Q https://youtu.be/Q1lL-hXO27Q