Quick question on big bang as expansion of space itself.

AI Thread Summary
The discussion centers on the concept that the Big Bang represents the expansion of space itself, with participants questioning the validity of this idea. Some argue that while space expands post-Big Bang, asserting that the Big Bang was the expansion itself raises concerns about the existence of anything outside it. Others suggest that a pre-Big Bang universe could be conceptualized as a balloon that expands, implying a larger context. The conversation also touches on the multiverse theory, emphasizing its hypothetical nature and lack of observational evidence. Overall, the debate highlights the complexities and uncertainties surrounding the Big Bang theory and the nature of the universe.
harroxelas
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Hello,

I've seen some scientists say on videos and write in books that big bang was the expansion of space itself. Is there actual evidence to support this? That space expands on a large scale after the big bang is ok but to say that the big bang was the expansion of space itself seems a bit odd to me.

IF the big bang was the expansion of space itself, seems like there's nothing outside the big bang, but we couldn't possibly klnow that!

Well, is there actual evidence to support this?
 
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Just look into Metric Expansion and such issues as superluminal galactic recession velocities... this isn't a tough one. You can probably get all you need from wikipedia.
 
harroxelas said:
Hello,

I've seen some scientists say on videos and write in books that big bang was the expansion of space itself. Is there actual evidence to support this? That space expands on a large scale after the big bang is ok but to say that the big bang was the expansion of space itself seems a bit odd to me.

IF the big bang was the expansion of space itself, seems like there's nothing outside the big bang, but we couldn't possibly klnow that!

Well, is there actual evidence to support this?

Indeed it is odd...but the only way in which this hypothesis can be maintained is if we take the previous pre-big bang universe and blow it up like a balloon so the space inside the balloon expands.

IF the big bang was the expansion of space itself, seems like there's nothing outside the big bang, but we couldn't possibly klnow that!

That's correct. In fact what exist outside the big-bang is another universe that provided the necessary ingridients for the current big-bang to take place.
 
Andrey said:
That's correct. In fact what exist outside the big-bang is another universe that provided the necessary ingridients for the current big-bang to take place.

If you work in Superstring/Multiverse area, shouldn't you mention that it is very hypotetical, and there are also other theories, without 'another universes', and there is no observational evidence to tell one from another? Your post can do more harm than good.
 
https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?

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