Light reaching Earth from quasar 3C273 has z=0.16.

(i) Outline what is meant by z.

(ii) Calculate the ratio of the size of the universe when the light was emitted by the quasar to the present size of the universe.

(iii) Calculate the distance of 3C273 from Earth using H_o=68kms⁻¹Mpc⁻¹.

Explain how cosmic microwave background (CMB) radiation provides support for the Hot Big Bang model.

(i)\(z = \frac{{\Delta \lambda }}{{{\lambda _o}}}\) where Δλ is the redshift of a wavelength and λ₀ is the wavelength measured at rest on Earth OR it is a measure of cosmological redshift

Do not allow just “redshift”.

(ii) \( \ll z = \frac{R}{{{R_o}}} - 1,\frac{R}{{{R_o}}} = \frac{1}{{z + 1}} \gg {\rm{so }}\frac{R}{{{R_o}}} =  \ll \frac{1}{{1.16}} \gg  = 0.86\)
Do not accept answer 1.16.

(iii) v=zc=0.16×3×10⁸=4.8×10⁴kms^-1
\(d = \frac{v}{{{H_o}}} = \frac{{4.8 \times {{10}^4}}}{{68}} = 706{\rm{Mpc}}\) OR 2.2×10²⁵m

as the universe expanded it cooled/wavelength increased

the temperature dropped to the present approximate 3K OR wavelength stretched to the present approximate 1mm

Value is required for MP2.