Symbol

Property

Definition

Ho

Hubble constant(an average of calculated values)

To

1/Ho

Present time or duration from the origin

T'

T' < To

Time of the observed event

H'

1/T'

H value calculated from time T' at a specific point

D'

D (T')

Distance at the time T'

v'

v (T')

Observed velocity at the time T'

${v^{″}}_{av}$

D'/T'

Average velocity from the origin to the time T'

H (obs)

v'/D'

Observed H value, or H value calculated from the velocity and the distance at a specific point.