Are Flat, Coplanar Orbits Only Found in Spiral Galaxies?

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Discussion Overview

The discussion revolves around the nature of the Big Bang theory and its distinction from cosmic inflation, as well as the types of galaxies where flat, coplanar star orbits may be found. Participants explore the definitions and implications of these concepts, particularly focusing on the characteristics of different galaxy types.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the accuracy of defining the Big Bang solely as "the expansion and cooling of the universe from an originally hot and dense state," suggesting it resembles a description of cosmic inflation.
  • Another participant affirms the initial description of the Big Bang, indicating it is a theory about the universe's evolution from a hot dense state.
  • A participant argues that the rapid expansion of the universe is more accurately associated with inflation, which they describe as a hypothesized part of the Big Bang that occurred in a very brief time frame after the singularity.
  • Concerns are raised about the use of "instantaneous" in describing the expansion, with one participant asserting that this term is misleading in a scientific context.
  • Participants discuss the characteristics of star orbits in different galaxy types, with one participant suggesting that only spiral galaxies contain stars in flat, coplanar orbits, while questioning the nature of orbits in irregular and elliptical galaxies.
  • Another participant supports the idea that irregular galaxies, formed through interactions, would likely have stars with more chaotic orbits.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of the Big Bang and cosmic inflation, with no consensus reached. There is also disagreement regarding the types of galaxies that may contain flat, coplanar star orbits, particularly between spiral and irregular galaxies.

Contextual Notes

Participants note the complexity of defining the Big Bang and inflation, highlighting the potential for misunderstanding due to the use of terms like "instantaneous." The discussion also reflects uncertainty about the orbital characteristics of stars in various galaxy types.

Sastronaut
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Hey PF! Have two questions here for everyone. Recently had a professor define the The Big Bang as "the expansion and cooling of the universe from an originally hot and dense state", but is this correct? To me it sounded more like the description of cosmic inflation...thoughts?

Additionally, was recently reading about galaxy types and star orbits. Which types of galaxies do you think astronomers would find stars that orbit in flat, coplanar orbits? My thought is solely spiral galaxies, but is that right? Do irregular or elliptical contain stars that orbit in such a manor? I didn't think irregular because i thought orbits would be all over place since irregular galaxies are created through collisions or galaxy's interacting and the resulting gravitation interaction would skew star orbits.


Thanks PF
 
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That is an excellent description of the big bang, which is indeed a theory that describes the evolution of the universe as an expansion from a hot dense state. Why do you think it is not?
 
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Because i have read that the (rapid) expansion of the universe is a descriptive for inflation and i have also seen the big bang theory defined simply as the instantaneous expansion of space and time...
 
Sastronaut said:
Because i have read that the (rapid) expansion of the universe is a descriptive for inflation and i have also seen the big bang theory defined simply as the instantaneous expansion of space and time...

Any description that says it was an instantaneous expansion is utterly wrong

Inflation is a hypothesized PART of the expansion from a hot dense state. It occurred (IF it occurred) in a very tiny fraction of a second, a tiny fraction of a second after the singularity, and caused an unbelievably massive expansion of the universe. By human standards this would have been for all practical purposes "instantaneous" however, as a scientific description of what happened, "instantaneous" is nonsense.

Inflation is not proven but it explains more than any other theory about the characteristics of the very early part of the expansion.
 
Phinds thank you for your help that makes much more sense now!
 

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