b_o3

thanks, but we're assuming no dark matter in the universe, what would the answer be then

Assume that the current age of the universe is 13.4 billion years old, and that we live in a matter-dominated, omega_m = 1, critical universe, what is the age of the universe at redshift 0.6? HINT: use the current age of the universe to pin down the proportionality relationship between age and the scale factor I know that (t_o) proportional to (1/H_o) proportional to (1/z), but I don't know how to connect this with the scale factor...and I have no idea how to "use the current age of the universe to pin down the proportionality relationship between age and the scale factor"

Hi, I really need help with this question I've tried everything! let's assume a critical/flat universe. Ho=70 km/s/Mpc. I computed Boltzman law for energy (volume) density by integrating Planck's law p rad= alpha*T^4. alpha= 7.56*10^-15 ergs/cm^3/K^4 (Which I computed to be 7.56*10^-16 Joules/m^3/K^4) I dont know where to begin with this question.. there's no other values provided . I'm supposed to somehow find out the redshift at which the universe switched from being radiation dominated to matter dominated (point of time at which radiation density is equal to mass density). and the temperature of the universe at that time .