Cosmological Redshift
The stretching of photon wavelengths to longer, redder values as light travels across the expanding space of the universe.
Governing formula
z = (λ_observed - λ_emitted) / λ_emitted, 1 + z = a(t_obs) / a(t_emit)
SI unit
Dimensionless Quantity (z)
In depth
Cosmological redshift is caused by the expansion of metric space during light transit, stretching the photon's wavelength proportionally to the cosmic scale factor ratio a(t_obs)/a(t_emit).
Examples in the real world
Detecting high redshift z > 10 in early galaxies using the James Webb Space Telescope (JWST).