Calling sequence of calc_t

The calling sequence for call_t is:

result = calc_t(z,$\Omega_M$, $\Omega_\Lambda$,H0=x,w=y,/year)

where x is a value for the hubble constant and y is a value for w ( $-1 \leq y \leq 0$). For ``normal'' physics, use w = -1 (see section IA above). z can be a scalar or an array. If it is scalar, result is a scalar lookback time. If z is an array, result is an array with the corresponding lookback time for each z value in the array. The parameters $\Omega_M$, $\Omega_\Lambda$ must be specified, whereas H₀ and w can be omitted (for the effects of this, see section IC below). H₀ has to be given in terms of $km/(Mpc\,\, s)$. If omitted, H₀ is internally set to 1 so the function returns as result the lookback time in terms of H₀ (see eq.  2). If w is omitted, it is internally set to -1. If the keyword /year is used, the result is given in years instead of seconds (see section IC below).