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Big Bang at every point in space?

  1. Nov 19, 2003 #1
    How does a Big Bang occur at every point in space. It is easy to comprehend something exploding at a point and sending everything outwards, but if something explodes (if we are even talking about the Universe exploding) at every point on and in itself, wouldn't it blow itself up or something, because every point is exploding then they would keep each other from expanding into each other and rather outwards. Seems like I just answered myself. Nevertheless, any thoughts?
  2. jcsd
  3. Nov 19, 2003 #2
    The Big Bang wasn't an explosion of anything, it was an expansion of space.

    In the balloon analogy, picture space as the surface of the balloon (not the interior, the surface), with all the matter as dots sprinkled over its surface. Run it back in time, so the balloon shrinks. The dots get closer and closer together. At the "Big Bang", the balloon has completely shrunk to zero size, and all the dots (all the locations in space) are at the same place.

    Or, picture an infinite plane with a uniform grid of dots in it. (They're really randomly spaced, but it's easier to picture a uniform grid). The dots are the galaxies and such. Now, half the distance between each dot: you get an infinite grid of points again, but they're denser. Keep doing that. In the limit, you have an infinite plane which is completely black, filled with an infinitely dense collection of dots. The Big Bang refers to the state that space was in, in this infinitely-dense condition: there is no particular location or dot that is the center of it all.
  4. Nov 20, 2003 #3


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    The "Big Bang" is poorly named. It causes confusion. Actually the name came from someone (Hoyle?) who was mocking the theory. But the name stuck.

    As Ambitwistor explained, it was nothing like an explosion we're familiar with. It was the beginning of time and space in our observable universe. At time = 0 (the beginning), the entire observable universe was contained within some yet-to-be-accurately-described seed (sometimes called the Big Bang singularity). Every point of space in the universe was contained in that seed (or perhaps it was just 1 point). Starting from the first instant of time, this seed rapidly expanded. Every point of space got farther apart from every other point everywhere in the universe. This Big Bang was happening everywhere in our universe. Of course, things looked very different. It wasn't until another 300,000 years after the beginning that the whole universe expanded and cooled enough for matter to form out of the soup of fundamental subatomic particles. Since the energy of the Bang, and thereby the fundamental particles, was everywhere in the universe, matter formed everywhere in the universe (i.e., matter was not exploded out from a central point into empty space). Once there was matter, gravity could pull that stuff together to form stars and galaxies. The universe is still coasting from the Big Bang event...still expanding in all direction (except for some localized areas where gravity wins out over expansion...like within a galaxy). A recent odd discovery is that the expansion now seems to be accelerating. But that is another story.
  5. Nov 20, 2003 #4
    This cleared things up, thanks. Maybe every point didn't grow apart from each other, but rather grew smaller, making it seem as they grew farther apart. :O
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