Question 1

How is Olbers's paradox explained?

Accepted Answer

The answer of How is Olbers's paradox explained?...

Question 2

The deuterium and lithium-7 in distant quasars and in the interstellar medium suggests that the universe is open.

Accepted Answer

The observation of deuterium and lithium-7 in distant quasars and the interstellar medium indicates a low density of baryonic matter in the universe, which suggests that the universe is open.

Question 3

The ____________________ is that the universe is both isotropic and homogeneous.

Accepted Answer

The answer of The ____________________ is that the universe is...

Question 4

The redshifts of the galaxies imply that the universe is expanding and that we are at the center.

Accepted Answer

The redshifts of the galaxies imply that the universe is expanding, but it does not imply that we are at the center. In fact, the universe does not have a center.

Question 5

The night sky is dark because the universe is not infinitely old.

Accepted Answer

The reason the night sky is dark is because the universe is not infinitely old. This is known as Olbers' paradox, which states that if the universe were infinitely old and uniformly populated with stars, then every line of sight would eventually end at the surface of a star, making the entire sky as bright as the surface of a star. However, since the universe is not infinitely old, there has not been enough time for light from all stars to reach us, resulting in a dark sky.

Question 6

How old is the universe since the Big Bang? Pick the best answer according to radioactive dating in the solar system, light travel times to most distant galaxies, time reversal of the Big Bang, and observations of the 3-K radiation.

Accepted Answer

The age of the universe according to radioactive dating of rocks and meteorites in the solar system, as well as observations of the cosmic microwave background radiation (3-K radiation), is approximately 14 billion years. Light travel times to the most distant galaxies also confirm an age of around 14 billion years. The time reversal of the Big Bang theory suggests that the universe is even older than 14 billion years, but this is not the most commonly accepted explanation for the age of the universe. Therefore, the best answer is D) 14,000,000,000 years.

Question 7

The elements hydrogen and helium were made during the first few minutes after the big bang.

Accepted Answer

During the first few minutes after the big bang, the universe was hot and dense enough for nuclear fusion to occur. This fusion produced the first elements, mostly hydrogen and helium.

Question 8

During its early history, matter dominated the universe.

Accepted Answer

The answer of During its early history, matter dominated the...

Question 9

COBE and WMAP measure the temperature of the cosmic background radiation to be ____________________.

Accepted Answer

The answer of COBE and WMAP measure the temperature of...

Question 10

The cosmic microwave background radiation was released shortly after the formation of the first stars.

Accepted Answer

The cosmic microwave background radiation was actually released about 380,000 years after the Big Bang during the era of recombination, when atoms formed and the universe became transparent to radiation. This radiation has since been detected and studied as a remnant of the early universe, providing important information about its properties and evolution.

Question 11

Observations of type Ia supernovae reveal that the expansion of the universe is speeding up because of the presence of ____________________ in empty space.

Accepted Answer

The answer of Observations of type Ia supernovae reveal that...

Question 12

The rate of expansion of the universe is currently increasing.

Accepted Answer

This is supported by observations and evidence from multiple sources, including the measurements of the cosmic microwave background, the distribution of galaxies, and the acceleration of distant supernovae.

Question 13

If the density of the universe is equal to the critical density, and H equals 50 km/s/Mpc, then the true age of the universe is 13.3 billion years.

Accepted Answer

This statement is known as the "Hubble Time" and assumes that the universe is flat and composed of normal matter and dark energy in the same proportions as observed today. With these assumptions, a Hubble constant of 50 km/s/Mpc yields an age of 13.3 billion years, given that the density of the universe is equal to the critical density needed to prevent it from collapsing under its own gravity. However, recent observations suggest that the universe may have a slightly different composition and geometry, which could affect its age calculations.

Question 14

If the average density of the universe is less than the critical density, the universe is open.

Accepted Answer

If the average density of the universe is less than the critical density, the gravity of the matter in the universe is not enough to halt the expansion of the universe. This means the universe will continue to expand forever, and is therefore considered open.

Question 15

According to the steady state theory, the universe did not expand.

Accepted Answer

According to the steady state theory, the universe was always expanding, but new matter was continuously created so that the density and overall appearance of the universe remained the same over time. This theory has been largely discredited in favor of the Big Bang theory, which posits that the universe began as a singularity and has been expanding ever since.

Question 16

The inflationary theory of the universe may explain why the background radiation is so isotropic.

Accepted Answer

The inflationary theory of the universe predicts that the universe expanded exponentially in its early moments, smoothing out any small-scale anisotropies and leaving the universe highly homogeneous and isotropic on large scales. This can explain why the background radiation, which is believed to have originated from this early period, appears so isotropic.

Question 17

A(n) ____________________ universe is infinite and would have a density equal to the critical density.

Accepted Answer

The answer of A(n) ____________________ universe is infinite and would...

Question 18

Most of the elements heavier than helium were made during the first few minutes after the big bang.

Accepted Answer

Elements heavier than helium, such as carbon and oxygen, were actually formed inside stars through the process of nuclear fusion. The only elements formed in the first few minutes after the big bang were hydrogen, helium, and a small amount of lithium.

Question 19

The ____________________ are theories that unify the electromagnetic, weak, and strong forces at extremely high energies.

Accepted Answer

The answer of The ____________________ are theories that unify the...

Question 20

The cosmological principle states that any observer in any galaxy will see the same general features of the universe.

Accepted Answer

The cosmological principle is a fundamental assumption used in modern cosmology and states that the universe is isotropic (looks the same in all directions) and homogeneous (looks the same at all locations) on a large scale. This means that any observer, no matter where they are located in the universe, will see the same general features of the universe, such as the distribution of galaxies and the cosmic microwave background radiation.

Quiz 14: Modern Cosmology