Question 5 (1 point) The cosmic
background radiation comes from a time in the evolution of the universe when
a."inflation"
was occuring. b.
electrons began to recombine with nuclei to form neutral atoms. c. gamma rays had enough energy to destroy nuclei. d. gravity began to pull material
together to form galaxies.
Question
6 (1 point) If the expansion rate is constant (no acceleration or deceleration) and H equals 100 km/sec/Mpc (not the
real value) then what
would be the age of the universe? (Hint: you can find the answer by comparing this value of H to the more realistic one
of 72 km/sec/Mpc which
implies 13.6 billion years (AKA Gyrs), as in class.)
a. 5 billion yrs b.10
billion yrs c.15 billion yrs d.
20 billion yrs
Worked this in class
before, so I’ll work it the other way.
Under this assumption, Age = 1/H.
If Age is 13.6 Gyrs for H = 72 km/s/Mpc, then Age for H = 100 km/s/Mpc can be
written thus:
Age(H=100)/Age(H=72)
= (1/100 km/s/Mpc)/(1/72 km/s/Mpc)
Age(H=100)/13.6
Gyrs = 72/100
Age(H=100)
= 10 Gyrs
As usual, pick the
closest answer. We don’t always know
numbers like H to precison.