Question 1

Observed mall fluctuations in the temperature of the cosmic microwave background are predicted by dark energy models.

Accepted Answer

The fluctuations in the cosmic microwave background are primarily predicted by models involving dark matter and the early universe's inflation, not dark energy. Dark energy is related to the accelerated expansion of the universe.

Question 2

The cosmic microwave background is the total of all the radio emissions from all the galaxies and quasars in the universe.

Accepted Answer

The cosmic microwave background is actually radiation left over from the Big Bang, not the radio emissions of all galaxies and quasars.

Question 3

An infinite universe is one of the assumptions of the cosmological principle.

Accepted Answer

False

Question 4

The fate or future of the universe depends only on the total number of galaxies and quasars.

Accepted Answer

The fate or future of the universe depends on several factors, including the amount of dark energy and matter and the rate of expansion. The total number of galaxies and quasars is not the only determining factor.

Question 5

Dark matter had no effect on the distribution of matter in the early universe.

Accepted Answer

Dark matter played a crucial role in determining the large-scale structure of the universe, including the distribution of matter in the early universe. Its gravitational effects helped to clump together ordinary matter and form the first galaxies and clusters of galaxies.

Question 6

The cosmological redshift is a direct measure of the expansion of the universe, thus independent of direction.

Accepted Answer

The cosmological redshift is caused by the stretching of the fabric of spacetime as the universe expands, and this effect is observed in all directions. Therefore, the cosmological redshift is independent of direction, making it a direct measure of the expansion of the universe.

Question 7

Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as
A) Obler's Paradox.
B) Hubble's Law.
C) Wien's Law.
D) the Cosmological Principle.
E) the Grand Unified Theory.

Accepted Answer

The assumptions of homogeneity (the universe looks the same in all directions) and isotropy (the universe looks the same at all locations) are known as the Cosmological Principle. This principle is a fundamental assumption in modern cosmology and forms the basis for many models of the universe's structure and evolution.

Question 8

Primordial nucleosynthesis refers to the Big Bang making all elements up to iron.

Accepted Answer

Primordial nucleosynthesis, or Big Bang nucleosynthesis, refers to the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, $^1H$, having a single proton as a nucleus) during the early phases of the universe. It primarily resulted in the formation of hydrogen-1, helium-4, helium-3, and traces of lithium-7. Elements heavier than lithium, up to iron, are mainly produced in stars and supernovae, not in the Big Bang.

Question 9

The cosmological redshift is actually not a velocity at all, but a measure of the expansion of space-time.

Accepted Answer

The cosmological redshift is caused by the expansion of space-time, which causes wavelengths of light to become stretched (shifted towards the red end of the spectrum). It is not a velocity in the traditional sense.

Question 10

The flatness problem is the fact that the observed density of matter is unexpectedly different from the critical density predicted by the inflationary epoch.

Accepted Answer

The flatness problem is about how the observed density of the universe is very close to the critical density, which makes the universe appear flat. This is unexpected without the fine-tuning introduced by the inflationary epoch, which explains why the universe appears flat and not due to a discrepancy between observed and critical density.

Question 11

The universe has been expanding at the same rate since its formation.

Accepted Answer

The rate of expansion of the universe has not been constant since its formation. The expansion rate has been known to accelerate due to the effects of dark energy.

Question 12

At decoupling, the electrons and protons were made from neutron decay.

Accepted Answer

At decoupling, electrons and protons already existed; decoupling refers to the time when photons stopped interacting frequently with these particles, allowing the universe to become transparent, not the creation of electrons and protons from neutron decay.

Question 13

The universe expanded by a factor of 10⁵⁰ during inflation, when the strong force separated from the electromagnetic and weak nuclear forces.

Accepted Answer

This is true according to the current accepted model of the Big Bang, which includes a period of rapid expansion known as inflation. During this period, the universe is thought to have expanded by an enormous amount, estimated to be a factor of at least 10⁵⁰. In addition, the forces that govern particle interactions are thought to have undergone a process called symmetry breaking, in which the strong force became distinct from the electromagnetic and weak nuclear forces.

Question 14

The Big Bang was an expansion of matter into empty space.

Accepted Answer

The Big Bang was not an expansion into empty space but rather an expansion of space itself, where all of space, time, and matter originated from a singular point.

Question 15

The low density universe is an open one, with expansion continuing forever.

Accepted Answer

The current scientific understanding is that the low density universe will continue to expand forever, making it an open universe.

Question 16

Not taking dark energy into account, we seem to live now in a matter dominated universe, since the observed matter density exceeds the observed energy density.

Accepted Answer

This is the current understanding of the universe, as observed matter (including both visible matter and dark matter) appears to dominate over the observed energy density. However, it should be noted that dark energy may play a significant role in the overall makeup and behavior of the universe.

Question 17

Decoupling refers to interactions between matter and antimatter at the end of the Radiation Era.

Accepted Answer

Decoupling refers to the point in the early universe where matter and radiation became separate, allowing the primordial radiation to travel freely through space. It is not related to interactions between matter and antimatter. Decoupling refers to the point in the early universe when matter and radiation became decoupled and the universe became transparent to radiation. It does not refer to interactions between matter and antimatter.

Question 18

The Hubble constant divided into the number one gives a rough estimate for the age of the universe, or the "Hubble Time."

Accepted Answer

The Hubble constant represents the expansion rate of the universe and if you divide it into the number one, it gives an estimate of the time it would take the universe to expand from its present size to its current state. This estimate is known as the "Hubble Time" and gives a rough estimate for the age of the universe.

Question 19

Deuterium was made only in primordial nucleosynthesis, since stars destroy it.

Accepted Answer

Deuterium, being the simplest type of heavy hydrogen, was formed during the early hot stages of the universe, in a process called primordial nucleosynthesis. It is also formed in small amounts in the interiors of stars but gets destroyed much faster than it gets created. Therefore, most of the deuterium we observe today is believed to be a relic of the Big Bang.

Question 20

What is the Great Wall?
A) It is a ridge on the Moon near the crater Birt.
B) It is the distance beyond which astronomers cannot view any more galaxies or even quasars.
C) It is a large sheet of galaxies.
D) It is the time before the universe started expanding, about which we can never know anything.
E) It is an enormous intergalactic cloud of dust and gas that hides more distant galaxies.

Accepted Answer

The Great Wall is a large sheet of galaxies that stretches across the universe for over 500 million light-years.

Note: None of the other options describe the Great Wall accurately.

Quiz 15: Cosmology and the Universe