Inflation-era schematic
The earliest fraction of a second is shown as a limited teaching diagram. The page does not claim to simulate quantum gravity or inflation dynamics.
Cosmic expansion lab
Big Bang means expansion from a hot dense early universe, not an explosion into empty space.
This page uses a Lambda-CDM expansion model to connect age, scale factor, redshift, CMB temperature, and the growth of large-scale structure. The simulation is a teaching model using real cosmological parameters; it is not a full numerical general-relativity or plasma-physics solver.
Age 13.8 billion years - scale factor 1.000 - redshift 0
Model parameters
What the simulation uses
Observable anchors
How the early universe is constrained
Interactive model
Scale factor, redshift, and cooling
Use the slider or play button to move through cosmic time. The readout computes redshift as z = 1/a - 1 and CMB temperature as T = 2.725 K / a.
Age 13.8 billion years - scale factor 1.000 - redshift 0
Cosmic Timeline
Important transitions
Hot plasma era
Radiation, electrons, protons, helium nuclei, dark matter, and neutrinos evolved in an opaque plasma; photons scattered frequently.
Recombination
Around 380,000 years after the hot dense early state, neutral atoms formed and photons began travelling freely as the CMB.
Dark ages
Before the first stars, matter kept clumping under gravity while the background radiation cooled and redshifted.
First stars and galaxies
Gas collapsed into the first luminous objects; feedback, mergers, and dark-matter halos shaped later structure.
Dark-energy domination
At late times the expansion rate becomes increasingly controlled by the dark-energy term in the Lambda-CDM model.
What is real here
Defensible simulation scope
The graph and readouts use the Friedmann expansion equation for a flat Lambda-CDM universe with matter, radiation, and dark-energy terms. The visual particles are comoving tracers, so their separation grows with scale factor while small density contrasts become galaxy-like structure.
What not to infer
Limits of this page
The Big Bang is not shown as a central explosion. The page does not solve early-universe quantum gravity, baryogenesis, inflation perturbation spectra, recombination radiative transfer, or N-body structure formation. Those require specialist numerical codes and survey data pipelines.
Mathematical model
Cosmological expansion model
The Big Bang page uses a scale-factor model to connect expansion, redshift, and cosmic temperature. The animation is a diagram of FLRW relationships, not an image-based explosion drawing.
Scale factor and redshift
\[1+z=\frac{1}{a(t)}\]
Redshift z is computed from scale factor a. This relation is the core proof that distance/stretch labels come from cosmology, not visual spacing alone.
CMB temperature
\[T=T_0(1+z)\]
The background temperature follows directly from redshift. The page's era changes are therefore tied to physical temperature scaling.
Expansion caveat
\[\mathrm{distance}_{\mathrm{display}}=f\!\left(a,\ \mathrm{comoving\ distance}\right)\]
The rendered spacing is a pedagogical map of expanding scale factor; it is not a literal object flying through pre-existing space.
Verification standard: the rendered object must be reproducible from stated equations, catalog parameters, or explicit geometric transforms. Visual reference images may inform presentation only; they are not the source of orbital positions, field vectors, accretion-disk gradients, timing, or engineering layout.
Limitations: browser scenes may use bounded scale, compressed distances, simplified two-body dynamics, schematic transfer curves, or educational approximations where full numerical ephemerides, CFD, finite-element models, or general-relativistic ray tracing are outside the page scope. Those simplifications are part of the model contract, not hidden image-based construction.