Question 1

Which of the following provides the strongest evidence for the classic Big Bang model?

Accepted Answer

The cosmic microwave background (CMB) radiation is the afterglow of the Big Bang and is present throughout the entire universe. The CMB provides strong evidence for the Big Bang because it has a blackbody spectrum consistent with a very hot and dense early universe, and it is almost completely uniform in temperature in all directions, which supports the idea of a sudden expansion from a single point. The age of the Solar System (A) does provide evidence for the age of the universe, but it does not specifically support the Big Bang model. The abundance of galaxies (C) is a consequence of the Big Bang, but on its own, it does not necessarily provide strong evidence for the Big Bang model. Therefore, the correct answer is B.

Question 2

When the cosmic microwave background was produced,it was a blackbody with a temperature of 4,000 K.Today,we observe it to have a temperature of 2.7 K.By approximately what factor has the Universe expanded between those two time periods?

Accepted Answer

The answer of When the cosmic microwave background was produced,it...

Question 3

According to our present understanding,in the distant future the Universe will:

Accepted Answer

This is based on the current understanding of the Universe's expansion and the influence of dark energy, which is causing the expansion to accelerate. It is believed that this acceleration will continue in the future, leading to an eventual "heat death" of the Universe where all matter is dispersed and the Universe is dark and cold. There is no evidence to suggest that the Universe will recollapse.

Question 4

Which of the following astronomers helped discover the cosmic microwave background?

Accepted Answer

Arno Penzias and Robert Wilson discovered the cosmic microwave background in 1964 when they were conducting experiments at Bell Labs in New Jersey.

Question 5

To what accuracy are the relative densities of dark energy and dark matter known,according to current cosmological measurements?

Accepted Answer

The relative densities of dark energy and dark matter in the universe are known to a precision of about 1 part in 100, according to current cosmological measurements. This level of precision is achieved through observations such as the cosmic microwave background radiation, galaxy clustering, and supernovae distances.

Question 6

Radiation from the first 400,000 years of the Universe's history can be observed as:

Accepted Answer

The radiation from the first 400,000 years of the Universe's history is known as the cosmic microwave background radiation, which is in the microwave region of the electromagnetic spectrum.

Question 7

A photon is emitted from a galaxy with a wavelength of 100 nm.By the time it reaches a telescope on Earth,the photon has a wavelength of 800 nm.By what factor has the Universe expanded between the photon's emission and detection?

Accepted Answer

The factor by which the Universe has expanded is given by the ratio of the observed wavelength to the emitted wavelength, which is 800 nm / 100 nm = 8.

Question 8

An alternate universe is filled with normal matter and dark matter,but not dark energy.If its density is twice the critical value,which curve on the figure below might represent its size?

Accepted Answer

The answer of An alternate universe is filled with normal...

Question 9

An astronomer discovers that the abundance of helium in the first galaxies to form in our Universe is only half that of small galaxies near the Milky Way.This would provide evidence:

Accepted Answer

The Big Bang model predicts a specific abundance of helium in the early Universe, and a significantly lower abundance in the first galaxies would contradict these predictions, providing evidence against the model.

Question 10

Which of the following correctly characterizes the composition of our Universe?

Accepted Answer

The current consensus among astrophysicists is that approximately 5 percent of the Universe is made up of normal matter (the stuff we can see and interact with), 27 percent is dark matter (which we cannot see but can observe via its gravitational effects on visible matter), and 68 percent is dark energy (which is responsible for the observed accelerating expansion of the Universe).

Question 11

The figure below shows a map of the temperature of the cosmic microwave background.The features shown here are instrumental in forming:

Accepted Answer

The temperature fluctuations shown in the map are instrumental in forming the cosmic web, the large-scale structure of the universe made up of galaxy clusters, filaments, and voids. These fluctuations were imprinted in the early universe and are visible as variations in the temperature of the cosmic microwave background radiation. The cosmic web is believed to have formed through the process of gravitational collapse, driven by variations in the density of matter in the early universe.

Question 12

Which of the following isotopes is NOT a potential probe of the first three minutes of the Universe's history?

Accepted Answer

Deuterium, helium-3, and lithium-7 were all produced in significant quantities during the first three minutes of the Universe's history, and thus their abundances can provide valuable information about that period. Carbon-13, on the other hand, is formed via a different process and its abundance is not as sensitive to the conditions of the early Universe. Therefore, it is not a potential probe of the first three minutes of the Universe's history.

Question 13

Why is baryogenesis NOT a key observational pillar of the classic Big Bang model?

Accepted Answer

The answer of Why is baryogenesis NOT a key observational...

Question 14

Why is the cosmic microwave background a blackbody?

Accepted Answer

The cosmic microwave background (CMB) is a blackbody because it was in thermal equilibrium with matter in the early Universe. As the Universe expanded and cooled, the CMB was left behind at a temperature of about 3 Kelvin, and it has not interacted significantly with matter since then. The blackbody spectrum of the CMB is a direct consequence of its thermal history.

Question 15

What process explains why the cosmic microwave background has nearly the same temperature in every direction on the sky?

Accepted Answer

The nearly uniform temperature of the cosmic microwave background is best explained by the process of inflation during the early universe, which expanded the universe rapidly and smoothed out any fluctuations in temperature.

Question 16

What process produced the initial density perturbations that would later grow into galaxies and galaxy clusters?

Accepted Answer

Inflation, an extremely rapid expansion of the universe in its earliest moments, is believed to have produced the initial density perturbations that would later evolve into galaxies and galaxy clusters. These perturbations were tiny variations in density that, over time, grew under the influence of gravity.

Question 17

Which of the following elements has an observed abundance that supports the Big Bang model?

Accepted Answer

Helium is the correct choice as it is one of the lightest elements and was predicted to have been produced during the Big Bang nucleosynthesis. Its observed abundance in the universe matches with the predictions of the Big Bang model. Iron, oxygen, and nitrogen, on the other hand, are heavier elements that are believed to have been produced in stars through nuclear fusion.

Question 18

Which of the following provides the best test of inflation?

Accepted Answer

Temperature fluctuations in the cosmic microwave background provide the best test of inflation because they are directly sensitive to the conditions that existed during the early inflationary epoch, and different inflationary models predict characteristic patterns of temperature fluctuations. The other options - the geometry of the Universe, nucleosynthesis, and the size of the observable Universe - can provide additional insights into the early Universe, but they are not as direct and powerful in testing inflation as the observations of the cosmic microwave background.

Question 19

What is the total density parameter of our Universe?

Accepted Answer

The total density parameter of the universe is the sum of the density parameter of matter (including both normal and dark matter) and the density parameter of dark energy. Recent observational data suggests that the density of matter is approximately 0.3 and the density of dark energy is approximately 0.7, giving a total density parameter of W = 1. Therefore, choice C is the correct option.

Question 20

Which of the following types of universes has the LOWEST density?

Accepted Answer

Negative curvature universes have the lowest density. This is because the negative curvature causes expansion to accelerate, spreading matter and energy apart and decreasing the overall density. Positive curvature universes have the highest density, while flat curvature universes have intermediate densities. Fluctuating curvature universes do not have a well-defined density.

Quiz 18: Cosmology