The Cosmic Web Sandbox

The cosmic web in a box, tunable. Turn the cosmological dials and watch the same patch of universe rearrange itself. Drag to rotate · scroll to zoom.

Cosmological parameters

Matter density Ω_m

More matter → stronger gravity, more small-scale structure

Clumpiness σ₈

Amplitude of fluctuations — smooth sea vs. dense knots

Spectral tilt n_s

<1 favours large structures, >1 favours small ones

Views

Splats: glowing points. Clouds: ray-marched density cloud.

Splat colors follow the local (single-stream) density.

Proxy halos = density peaks; galaxies via Zheng et al. (2004) HOD model.

HOD log M_min

HOD log M₁

satellite slope α

Which halos host a galaxy, the mass per extra satellite, and how fast satellites multiply.

Power spectrum

Measured P(k) from the box (dots) vs linear input (line). Halos/galaxies show bias and shot noise.

Cosmic time

Scale factor a

Tip: switch to Web type colors to watch gravitational collapse in 1, 2, then 3 axes assemble sheets → filaments → nodes.

Cosmology presets

One-tap parameter sets to compare at a glance.

Simulation configurations

Displacement model. 2LPT sharpens filaments and knots.

Redshift space: infall stretches structure along the line of sight (Kaiser).

Fixed seed across parameters — same phases, as in the AbacusSummit movie.

Power spectrum P(k)