The farther a galaxy, the faster it recedes. The recession velocity is linear in distance — v = H₀·d — and it has no centre: every galaxy sees the same law, because space itself is stretching. Rendered, not quoted.
source Hubble, E.P. (1929), A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae, PNAS 15(3), 168–173 · doi:10.1073/pnas.15.3.168
A galaxy at distance d recedes with velocity v set by one constant, the Hubble parameter H₀:
v = H₀ · d (H₀ ≈ 70 km/s/Mpc)A straight line through the origin. Double the distance, double the speed. The slope is H₀; its reciprocal 1/H₀ is a timescale.
Uniform expansion means a single scale factor a(t) multiplies every separation, so ḋ = (ȧ/a)·d = H₀·d for all pairs at once.
Farther is faster. Hubble 1929 turned nebular redshifts into a law: v = H₀d, no centre, Hubble time 1/H₀ ≈ 14 Gyr.
Upstream, the expansion is governed by the-friedmann-equation. Downstream, the stretch is read off light by the-cosmological-redshift. This sphere is the middle term: the observed straight line.
Live re-check of the engine's invariants. Confirms green; flips red the instant the machine is tampered.
A distance d in megaparsecs (Mpc). Drag it. The engine returns the recession velocity live.
v = H₀·d, computed live. The line, the Hubble distance where v = c, and the expanding lattice.
Proven at boot, deterministically:
“A recession law implies we are at the centre of an explosion.”
Real objection, real answer. Because v = H₀d is linear and the expansion multiplies every separation by one factor a(t), the same law holds from every galaxy's frame — the vector velocity from B is H₀(r₀₋r_B). No point is privileged; there is no centre and no edge. The redshift is stretched space, not a Doppler flight through it.
Planted void (disclosed): replace the law with v = H₀·d² (quadratic). Now a galaxy twice as far recedes 4× faster, not 2× — a preferred centre reappears and homogeneity dies. The Witness (7) catches it.