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Conceptual Questions



1

Under what conditions would the expansion age of the universe be the actual length of time that has passed since the Big Bang?
2

Suppose astronomers were to discover that the value of Hubble's constant were twice as large as it is now thought to be. What effect would this discovery have on the expansion age of the universe?
3

Suppose we use Hubble's law to find that the galaxies at a distance of 200 Mpc were adjacent to the Milky Way 12 billion years ago. How long ago were the galaxies at 400 Mpc adjacent to the Milky Way?
4

What is meant by the statement that the surface of a ball has no center?
5

Compare flat space universes with positively curved universes with respect to whether they are finite, whether they are bounded, and whether they have centers.
6

Describe two geometrical tests that could be used to distinguish positively curved universes from flat universes.
7

Describe two geometrical tests that could be used to distinguish positively curved universes from negatively curved universes.
8

Suppose you lived in a two-dimensional universe. Describe how you could use counts of distant galaxies to learn the curvature of space in your universe.
9

What is the curvature of the universe if its density is less than the critical density?
10

What is the value of V0 if the universe is flat?
11

What combination of Hubble's constant and density can produce a universe in which expansion will continue forever?
12

What is the relationship between the value of V0 and the extent to which the expansion age of the universe differs from the actual age of the universe?
13

How do ancient supernovae contribute to the idea that expansion may be accelerating?
14

Why did Einstein invent the cosmological constant?
15

How would dark energy affect the expansion of the universe?
16

How can globular clusters be used to place a lower
17

Why did pair production stop when the universe was 1 second old?
18

What was the origin of the primordial neutrinos that are still present in the universe?
19

Why were conditions right for the production of helium from hydrogen only between 100 and 300 seconds after the universe began?
20

What happened to all of the radiation that was produced during the first few hundred thousand years after the universe began?
21

The cosmic background radiation was emitted by gas at a temperature of about 3000 K. Why, then, is the CBR brighter in the radio part of the spectrum than at visible wavelengths?
22

What is meant by the statement that the CBR has a temperature of 2.74 K?
23

What do fluctuations in the brightness of the CBR tell us about the universe?
24

Why is the isotropy of the CBR a problem for the standard Big Bang model?
25

Why is the present flatness of the universe a problem for the standard Big Bang model?
26

Describe how inflation solves the flatness problem of the standard Big Bang.
27

What is the fate of the universe if it has positive curvature and there is little or no dark energy?







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