Question 1

Which of the following observations provides the most direct evidence for the expansion of the universe?

Accepted Answer

The redshift of light from distant galaxies

Question 2

According to Hubble's Law, what is the relationship between the recessional velocity $$v of a $$galaxy and its distance $$d$$ from Earth?

Accepted Answer

$$v = H_0$ d$$

Question 3

Why does the light from distant galaxies appear redshifted?

Accepted Answer

Because the space between galaxies is expanding, stretching the light waves

Question 4

What is the estimated age of the universe based on current cosmological evidence?

Accepted Answer

$$13.8 \pm 0.2$$ billion years

Question 5

Which of the following is NOT a piece of evidence supporting the Big Bang theory?

Accepted Answer

The existence of black holes in the centers of galaxies

Question 6

During which era did protons, neutrons, and electrons first form in the universe?

Accepted Answer

Particle Era

Question 7

What is the significance of the cosmic microwave background (CMB) radiation?

Accepted Answer

It is the redshifted glow from the Big Bang, providing a snapshot of the early universe

Question 8

Why can we not observe the universe at times earlier than about 500,000 years after the Big Bang?

Accepted Answer

Because photons were constantly scattered by free electrons, making the universe opaque

Question 9

Which process is responsible for the creation of elements heavier than iron in the universe?

Accepted Answer

Supernova explosions

Question 10

If the universe is dominated by 'dark energy,' what is the expected fate of the universe according to current evidence?

Accepted Answer

Its expansion will accelerate forever

Question 11

What is the current composition of the universe in terms of matter and dark energy?

Accepted Answer

About $$1/3$$ matter and $$2/3$$ dark energy

Question 12

Which analogy best describes the expansion of the universe?

Accepted Answer

Raisins moving with the dough as the dough itself expands

Question 13

Why is looking farther out into space equivalent to looking back in time?

Accepted Answer

Because light from distant objects takes time to reach us

Question 14

What is the predicted primordial mass ratio of hydrogen to helium from the Big Bang nucleosynthesis?

Accepted Answer

$$3:1$$

Question 15

Which structure best describes the large-scale distribution of galaxies in the universe?

Accepted Answer

A soap-bubble structure with galaxies on the surfaces and voids inside

Question 16

During the Era of Nucleosynthesis, which elements were primarily formed?

Accepted Answer

Hydrogen, helium, and traces of lithium

Question 17

What would have happened if the universe had produced exactly equal amounts of matter and antimatter during the Particle Era?

Accepted Answer

The universe would contain only photons today

Question 18

Which event marks the transition from the Era of Nuclei to the Era of Atoms?

Accepted Answer

The capture of free electrons by hydrogen and helium nuclei, making the universe transparent

Question 19

A galaxy is observed to be 1,000 megaparsecs away and is receding at 70,000 km/s. What is the value of the Hubble constant $$H_0 in$$ $$\mathrm{km\,s$$^{-1}$$\,$$Mpc^{-1}$$}$$?

Accepted Answer

$$H_0 = 70$$\ \mathrm{km\,$$s^{-1}$$\,$$Mpc^{-1}$$}$$

Question 20

Which of the following best explains why we can never see back in time beyond 500,000 years after the Big Bang?

Accepted Answer

The universe was opaque to photons before this time due to free electrons scattering light

Cosmology and the Evolution of the Universe: A Physics Study Guide

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