Extended Features:

  1. We will expand a bit on the eras of cosmic history in the following items.

  2. Inflation is a hypothetical super rapid exponential increase expanding universe phase from a minute early universe embedded in a false vacuum universe.

    The paradigm (i.e., a grand vaguely specified theory) of inflation was introduced in 1979--1981 and significant evidence as accrued for it. But alternative theories exist.

    By the by, the false vacuum universe may also be the multiverse. But that is a very speculative theory. Maybe theory of everything (TOE) (if it is ever discovered) will prove or disprove the multiverse paradigm.

  3. In yours truly's view the Big Bang itself is the early post inflation period in which the primoridal light elements (i.e., the aforementioned hydrogen (H-1), deuterium (D, H-2), helium (He-3), helium-4 (He-4), and lithium-7 (Li-7)) were synthesized: i.e., the Big Bang nucleosynthesis era (cosmic time ∼ 100--1000 s = 1.7--17 m).

    Immediately after this phase, mass-energy of the observable universe consisted of the matter (i.e., the aforementioned primoridal light elements), cosmic background radiation (CBR) (which was a blackbody radiation field in in thermodynamic equilibrium with the matter), cosmic neutrino background, dark matter and and dark energy (which is a name for our ignorance of the cause of the accelerating universe).

  4. The primordial gas (of matter and electromagnetic radiation (EMR)) cooled with expansion of the universe via the ordinary thermodynamics process of adiabatic expansion.

  5. At about 380,000 years after the Big Bang (when the temperature was ∼ 3000 K) occurred the recombination era when the ionized hydrogen (H-1) gas (which just consists of free protons) recombined with the free electrons to create a neutral hydrogen (H-1) gas. The neutral hydrogen (H-1) was much more transparent to photons than the previous ionized hydrogen (H-1) gas and this resulted in the decoupling era which is when the cosmic background radiation (CBR) essentially stopped interacting with matter. Since then it has mostly just free streamed through space and adiabatically cooled to become the present-day cosmic microwave background (CMB) which still is a blackbody radiation field with a temperature CMB T = 2.72548(57) K (Fixsen 2009).

  6. The primordial gas of matter was initially fairly uniform in density, but there was a spectrum of fluctuations (or perturbations) from the mean density which in inflation cosmology were set in the inflation era itself.

    The fluctuations led to clumping where density was high and declumping where it was low It was a case of the rich getting richer and the poor getting poorer.

    The overall process is called structure formation (AKA large-scale structure formation).

    Structure formation created galaxies, galaxy clusters, galaxy superclusters, galaxy filaments, and cosmic voids: i.e., all the large-scale structure of the universe which nowadays is often called cosmic web which is NOT quite a synonym for large-scale structure since it is the particular form of large-scale structure we actually have.

  7. Structure formation was primarily driven by the dark matter with baryonic matter (i.e., protons, neutrons, and electrons) largely following

    The galaxies, in fact, formed in gravitational wells of dark matter which we call dark matter halos.

    Of course, in the galaxies, there was star formation.

  8. The first galaxies formed earlier than ∼ 0.35 Gyr after the Big Bang era (cosmic time to ∼ 20 m) (see Wikipedia: GLASS-z12 (oldest known galaxy c.2023)).

  9. Since the first gigayear (Gyr), galaxies and the large-scale structure have continued to evolve.

    The expansion of the universe continues to spread apart gravitationally unbound systems.

    Within gravitationally bound systems (i.e., galaxies and galaxy clusters), the galaxies continue to evolve by galaxy mergers and galaxy quenching (i.e., the turning off of star formation). See galaxy formation and evolution.


    The Big Bang and evolution since then form a well established theory: it would be extremely surprising if that theory were just plain wrong.

    Cosmic evolution before the Big Bang (i.e., the multiverse and inflation) is much more speculative---one of those deep mysteries of modern physics.

    It wouldn't be extremely surprising if the multiverse and inflation were just plain wrong.

    Theories have different statuses as mentioned above.

File: Cosmology file: cosmos_history_1bb.html.