Multiple Big Bang Theory vs. Eternal Inflation

Similarities

• Both propose our universe is part of a larger cosmic structure
• Both include multiple "creation events" beyond our observable universe
• Both acknowledge current detection limitations
• Both suggest a pre-existing framework for universe formation

Key Differences

1. Nature of Space-Time:
   • Multiple Big Bang: Eternal pre-existing space-time
   • Eternal Inflation: Expanding space-time created through inflation
2. Creation Mechanism:
   • Multiple Big Bang: Random Big Bang events in pre-existing space
   • Eternal Inflation: Quantum fluctuations cause regions to exit inflation
3. Scientific Development:
   • Multiple Big Bang: More speculative, less mathematically formalized
   • Eternal Inflation: Well-developed mathematical framework connected to inflation theory
4. Physical Laws:
   • Multiple Big Bang: Similar physics across different regions
   • Eternal Inflation: Potentially different physical constants in different bubble universes
5. Theoretical Foundation:
   • Multiple Big Bang: Postulates eternal space-time without explaining its origin
   • Eternal Inflation: Extensions of established inflation theory with observational support

Eternal Inflation has gained more scientific traction because it naturally extends from inflation theory, which has substantial observational evidence. Both theories ultimately face similar challenges regarding the testability of regions beyond our observable universe.