Recessional Velocity Calculator

Calculate the recessional velocity of a galaxy based on its redshift value and distance. This calculator uses Hubble's Law.

Input Parameters

Calculation Results

Calculation Formula

v = H₀ × d

Where:
v = recessional velocity (km/s)
H₀ = Hubble constant (approximately 70 km/s/Mpc)
d = distance (Mpc)

Recessional Velocity Calculator Usage Guide

Learn how to use the Recessional Velocity Calculator and understand its scientific principles

How to Use This Calculator

  1. Enter the redshift value (z) of a galaxy. Redshift is a measure of how much the light from a galaxy has been stretched toward the red end of the spectrum due to its recessional motion.
  2. Enter the distance to the galaxy in Megaparsecs (Mpc). A parsec is approximately 3.26 light-years.
  3. Optionally, adjust the Hubble constant (H₀) if you want to use a different value (the standard value is 70 km/s/Mpc).
  4. Click the "Calculate" button to compute the recessional velocity.

Understanding Reccessional Velocity

Recessional velocity is the speed at which a galaxy is moving away from us. This phenomenon is observed due to the expansion of the universe. The relationship between recessional velocity and distance is described by Hubble's Law:

v = H₀ × d

where v is the recessional velocity, H₀ is the Hubble constant, and d is the distance to the galaxy.

Example

If a galaxy has a distance of 50 Mpc and we use the standard Hubble constant of 70 km/s/Mpc, the recessional velocity would be:

v = 70 km/s/Mpc × 50 Mpc = 3,500 km/s

Scientific Significance

The measurement of recessional velocities provides evidence for the expansion of the universe. The faster a galaxy is moving away from us, the farther away it is, creating what is known as Hubble's Law. This relationship was first discovered by Edwin Hubble in the 1920s and provided strong evidence for the Big Bang theory.