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701 sats \ 2 replies \ @elysia 19 Dec 2023 \ on: What was before the big bang? Ask_SN
  1. Quantum Fluctuations:
    • In the realm of quantum field theory, the concept of a vacuum is redefined. A vacuum state is subject to the Heisenberg Uncertainty Principle, which allows for the temporary creation of particle-antiparticle pairs, known as virtual particles.
    • The hypothesis posits that during the Planck epoch (the earliest period of the universe, at the Planck scale), a quantum fluctuation could have initiated the Big Bang. This fluctuation, within an inflationary framework, could have caused a rapid expansion, magnifying quantum irregularities into the large-scale structures observed in the universe today.
  2. No Time Before the Big Bang:
    • In the context of General Relativity, time is a dimension intertwined with the three spatial dimensions. The singularity at the Big Bang represents a breakdown of classical notions of spacetime.
    • Theoretical models like the Hartle-Hawking state propose that time, as a familiar concept, didn’t exist before the Big Bang but emerged along with the universe. In these models, the universe doesn't have a singular beginning but is described as a closed surface without boundary, analogous to the surface of a sphere.
  3. Multiverse Theories:
    • In inflationary cosmology, particularly eternal inflation, our universe could be one of many within an ever-inflating multiverse. Regions where inflation stops can lead to "bubble universes" with distinct physical properties.
    • String theory’s landscape suggests a vast number of possible vacuum states, each corresponding to different fundamental constants and laws of physics, potentially realizing the multiverse concept.
  4. Cyclic Models:
    • Modern cyclic models, like the ekpyrotic universe, propose a scenario where the Big Bang is the result of the collision of two three-dimensional worlds (branes) in a higher-dimensional space.
    • These models attempt to address issues like the homogeneity and flatness of the universe, and the generation of gravitational waves, without requiring a singular beginning.
  5. String Theory and Higher Dimensions:
    • String theory replaces point-like particles with one-dimensional "strings". These strings' vibrations correspond to different particles. The theory requires extra spatial dimensions for consistency: ten for superstrings and eleven for M-theory.
    • In brane cosmology, a subset of string theory, our universe could be a 3-brane embedded in a higher-dimensional bulk. Interactions within this bulk, such as brane collisions, could manifest as cosmological events in our 3-dimensional universe.
  6. Unknown Physics:
    • Concepts like loop quantum gravity aim to merge quantum mechanics and general relativity, potentially offering insights into the pre-Big Bang universe. This theory posits that spacetime itself is quantized, with implications for the structure of the universe at the Planck scale.
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0 sats \ 1 reply \ @Undisciplined 19 Dec 2023
Great job summarizing so many of the hypotheses and the formatting is so much nicer than I would have done.
I tend towards explanation 2. Time isn't what we conceive it as and the concept of "before the Big Bang" might just be incoherent.
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0 sats \ 0 replies \ @south_korea_ln 11 Dec
I think explanation 2, i.e. the concept of time being a consequence of the bigbang itself, is the prevailing belief in the scientific community. It this case, it would thus not make sense to talk about something "before the big bang".
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