Interactive cosmology

Explore the distance–redshift relation.

Move the sliders and watch cosmological distances change with redshift in a flat ΛCDM universe.

Distance relation

Plot

—Mpc at z = 1.00

Inspect redshift 1.00

Comoving, D₍C₎—Mpc

Angular diameter, D₍A₎—Mpc

Luminosity, D₍L₎—Mpc

Survey volume

Comoving volume to redshift z.

Choose the fraction of the full sky observed. The result is the flat-universe comoving volume enclosed by your selected redshift.

Sky fraction, f_sky 0.100

Equivalent area: — deg²

V_c(z)—Gpc³

What you are seeing

The calculation, not a black box.

For flat ΛCDM, the expansion rate is E(z) = √[Ωₘ(1+z)³ + ΩΛ]. The comoving distance is the numerical integral of c / [H₀E(z)] from 0 to z. D₍A₎ = D₍C₎/(1+z) and D₍L₎ = (1+z)D₍C₎.

For the volume, V_c(z) = (4π/3) f_skyD₍C₎³. Every slider event recalculates in your browser and redraws the plot; no server is involved.

This teaching version ignores radiation and assumes spatial flatness. A future Astropy version could add named cosmologies, radiation, curvature and further distance measures.