Chapter 81, The Beginnings of the Universe Video Solutions, Pathways to Astronomy

Problem 1

One second after the Big Bang, the density of the universe was about $0.1 \mathrm{kg} / \mathrm{L}$.
a. How big a volume of the universe contained as much mass as the Solar System?
b. Estimate approximately how much bigger the universe would have been after three minutes. How big would the Solar System mass region be then? Compare this to the present size of the Solar System.

Matthew Miranda

Numerade Educator

02:21

Problem 2

How much energy is released when an antiproton and a proton collide? Compare this energy to the energy released when four protons combine to make a helium nucleus in a star.

Sarah Mccrumb

Numerade Educator

01:44

Problem 3

As inflation began, the size of the universe (the currently visible universe) expanded from about $10^{-30} \mathrm{m}$ to twice that size in $10^{-35}$ sec. Calculate Hubble's constant at that time, converting it to the same units used today. In the next $10^{-35}$ sec the size of this region doubled again. Show that Hubble's constant remains the same.

Sarah Mccrumb

Numerade Educator

11:44

Problem 4

Examine Figure $81.7 \mathrm{B}$. The map in the figure is $360^{\circ}$ wide and $180^{\circ}$ tall. An angle of $1^{\circ}$ on this map corresponds to about
$250 \mathrm{kpc}$.
a. Approximately how big are the largest high-density regions you see, in degrees? How large is this in kiloparsecs?
b. How large a region would that be today?
c. Relate this size to components of the large-scale structure we see today (Unit 76).

Mark J

Numerade Educator

01:40

Problem 5

cosmologists have commented that the universe expanded more in the $10^{-33}$ sec of inflation than in the rest of the history of the universe. What they are referring to is the relative amount of expansion-the ratio of size at the end to the initial size. Compare the amount of expansion that occurred during inflation (doubling in size 100 times over) to the expansion of the present visible universe (13.7 billion ly in radius) from a region with just a $1-\mathrm{cm}$ radius.

Zulfiqar Ali

Numerade Educator

06:08

Problem 6

Compare the amount of energy released when a proton and antiproton annihilate each other to the energy released when four protons fuse to form helium.

Mark J

Numerade Educator