Pathways to Astronomy

Stephen E. Schneider

Chapter 79 Cosmology - all with Video Answers

Educators

Chapter Questions

Problem 1

When Hubble first estimated the Hubble constant, galaxy distances were still very uncertain, and he got a value for $H$ of about $600 \mathrm{km} /$ sec per Mpc. What would this have implied about the age of the universe? What problems would this have presented for cosmologists?

Zulfiqar Ali

Numerade Educator

02:09

Problem 2

A galaxy at a distance of 25 Mpc has a recession velocity of $1,875 \mathrm{km} / \mathrm{sec} .$ What is Hubble's constant based on this one galaxy? Why is this not a good way to determine Hubble's constant?

Sarah Mccrumb

Numerade Educator

01:44

Problem 3

Hubble's constant is still not precisely known. Calculate $t_{H}$ for two other values of Hubble's constant currently favored by some astronomers:
a. $H=71 \mathrm{km} / \mathrm{sec}$ per Mpc.
b. $H=65 \mathrm{km} / \mathrm{sec}$ per Mpc.

Sarah Mccrumb

Numerade Educator

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Problem 4

What wavelength would visible light $(400 \text { to } 700 \mathrm{nm})$ have if it were seen from a galaxy formed just half a billion years after the Big Bang? What if it came from matter when the universe was just $400,000 \text { years old? (Refer to Table } 79.1 .)$

Michelle Z.

Numerade Educator

00:17

Problem 5

Plot the light travel time ( $Y$ axis) versus the redshift ( $X$ axis) based on the data from Table 79.1 . Estimate the redshift for galaxies that are seen as they were $1,2,$ and 3 billion years ago.

Zachary Warner

Numerade Educator