I Expanding universe needs a big bang?

AI Thread Summary
The discussion centers on the relationship between the Big Bang and the current expansion of the universe, particularly regarding the role of dark energy. Participants argue that while dark energy is responsible for the acceleration of expansion, the Big Bang is crucial for establishing the initial conditions necessary for this expansion to occur. The Big Bang is not merely a creation event but a phase that set the stage for the universe's evolution, including the formation of matter and cosmic structures. Some participants express skepticism about the necessity of the Big Bang in explaining current expansion, suggesting that dark energy alone could suffice. Ultimately, the conversation highlights the complexity of cosmic expansion and the interplay between historical events and current phenomena.
  • #101
Michaela SJ said:
doesn't anything shorter than the length of Planck Time foreclose knowing what happened at the moment of the Big Bang.

The "moment of the Big Bang" in our best current cosmological model is not an "initial singularity". It's the hot, dense, rapidly expanding state that is the earliest state of the universe for which we have good evidence. In inflationary models, it's the state at the end of inflation, just after "reheating" has occurred.
 
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  • #102
Michaela SJ said:
ed
Pardon my impertinence, but doesn't anything shorter than the length of Planck Time foreclose knowing what happened at the moment of the Big Bang.

You're confusing the big bang as a single 'event' (creation of the known universe) with the big bang as a 'process' (rapid expansion from a hot, dense state). Bandersnatch is referring to the latter.
 

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