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 The Hubble
constant, which we measure to be about 72 km/s/Mpc, describes the current expansion rate of
the local universe. We think the age of the universe is about 14 billion years, in
the context of the Big Bang theory. If the Hubble constant were much larger, say 500
km/s/Mpc as Edwin Hubble first reported, then how would our estimate of the age of the
universe change?
a.It would still be about the same.
b.It would be larger, about 7 times
larger (500/72), or nearly 100 billion years old.
c.It would be much smaller, about 7 times
smaller, or about 2 billion years old.
Age
is inversely proportional to the Hubble constant for essentially all
models. Age ~ 1/H. So if the Hubble constant is larger, the
time is smaller. Under this assumption,
Age = 1/H.
Age(H=500)/Age(H=72) = (1/500 km/s/Mpc)/(1/72
km/s/Mpc)
Age(H=500)/13.6
Gyrs = 72/500
Age(H=500)
= 2 Gyrs
As usual, pick the
closest answer. We don’t always know
numbers like H with high precision.