The Big Bang model is an attempt to explain a host of observations that tell us how the universe evolved from its first fraction of a second onwards.

However, it does not explain clearly what dark energy or matter is, and how the universe was created at the very start.

So is the Big Bang theory a complete model of the universe?

Edited January 30, 20232 yr by caryunxwn
typo

The Big Bang (BB) is a model of how the universe evolved about 13.8 billion years ago. I don't think it says anything about the current size or shape of the universe, or what the universe's future will be like, although researchers are always studying that. The point of dark energy is that it looks like the universe might keep expanding forever, but that's still very speculative.

Big Bang theory also doesn't say anything about what happened more than 13.8 billion years ago, except to the extent that the BB is interpreted as the "beginning" of the universe, which would mean that nothing happened before that, or that "before that" has no meaning.

Dark matter and dark energy are still mysteries to current theory, so the BB (plus general relativity and the Standard Model) can't be considered a "complete" theory in the sense of explaining them. It's also not complete in the sense that there's no theory of what happened in the first 10^-43 seconds* after the theorized singularity (the Planck era), because we still don't have a theory that combines gravity and quantum mechanics, both of which were important then, according to the theory.

 

* 10^-43 seconds is 100 quadrillionths of a quadrillionth of a quadrillionth of a second.

Edited January 30, 20232 yr by Lorentz Jr

Essentially the "big bang" theory is a theory based on what we can measure/observe, anything beyond this is speculation.

So in answer to your question, "is the big bang theory a complete model?", well the answer is no. It is a model, of the observable universe both present and in the past.  

Edited January 30, 20232 yr by Intoscience
spelling

In the words of Alan Guth, the BB theory does not say what banged, why it banged, and what happened before it banged. No, it's not complete.

4 hours ago, Lorentz Jr said:

The Big Bang (BB) is a model of how the universe evolved about 13.8 billion years ago. I don't think it says anything about the current size or shape of the universe, or what the universe's future will be like, although researchers are always studying that. The point of dark energy is that it looks like the universe might keep expanding forever, but that's still very speculative.

Big Bang theory also doesn't say anything about what happened more than 13.8 billion years ago, except to the extent that the BB is interpreted as the "beginning" of the universe, which would mean that nothing happened before that, or that "before that" has no meaning.

Dark matter and dark energy are still mysteries to current theory, so the BB (plus general relativity and the Standard Model) can't be considered a "complete" theory in the sense of explaining them. It's also not complete in the sense that there's no theory of what happened in the first 10^-43 seconds* after the theorized singularity (the Planck era), because we still don't have a theory that combines gravity and quantum mechanics, both of which were important then, according to the theory.

 

* 10^-43 seconds is 100 quadrillionths of a quadrillionth of a quadrillionth of a second.

Nice summary! +1

Article in Universe Today from 5th March 2023,  seems to suggest that there could be a 2nd big bang which produced Dark Matter.

https://www.universetoday.com/160285/the-universe-may-have-started-with-a-dark-big-bang/

Which seems an interesting idea, to try and explain where dark matter comes from.

 

Paul