Redshift Calculator

This java applet allows you to calculate look-back times, distances, and recessional velocities for arbitrary values of the Hubble constant H and the deceleration parameter q. The calculator assumes the cosmological constant to be zero. The relativistic formula is used to relate v/c to the redshift z. The calculator uses a short-hand scientific notation. For example,

9.73E-9 = 9.73 x 10^-9

and so on. The last field gives the lookback time in terms of the fraction of the age of the Universe when the light was emitted. For example, if this number is 0.14, the light was emitted when the Universe was only 14 percent of its present age (with the age depending on the Hubble and deceleration parameters that were input). Usage: Use the sliders to enter values for the Hubble constant and the deceleration parameter. Then the recessional velocity, distance, look-back time in years, and the fraction of the age of the Universe corresponding to when the light was emitted are calculated for each redshift input in the top field.