Suppose the ionization energy of hydrogen were larger than 13.6 eV and the decoupling of radiation and matter had occurred earlier, say at z = 2000. What would the temperature have been at that time?
A)2500 K
B)3000 K
C)3500 K
D)5500 K

Question

Quizplus · Accepted Answer

The temperature at the time of decoupling is related to the redshift z by the formula T = T0 * (1 + z), where T0 is the current temperature of the cosmic microwave background, approximately 2.7 K. At z = 2000, the temperature would be 2.7 K * 2000 = 5400 K, which is closest to 5500 K.

Suppose the Ionization Energy of Hydrogen Were Larger Than 13