Chapter 23
Basic Skills/Definitions Quiz
Part A
Based on our current understanding of physics, it would seem that we can understand the conditions that prevailed in the early universe as far back in time as ______.
Hint A.1
Study Section 23.1
ANSWER:

one ten-billionth of a second after the Big Bang. 3 minutes after the Big Bang. 10 billion years ago. 380,000 years after the Big Bang.
Part B
What happens when a particle of matter meets its corresponding antiparticle of antimatter?
Hint B.1
Study Section 23.1
ANSWER:

They can form a complete atom. The combined mass-energy of the two particles is completely transformed into radiation-energy (two photons). They fuse to make a heavier particle. The question makes no sense, since antimatter does not really exist.
Part C
What is the significance of the Planck time?
Hint C.1
Study Section 23.1
ANSWER:

Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred. It is the time when the cosmic microwave background was released. It is the amount of time required for two protons to fuse to make deuterium. It is the time at which inflation is thought to have occurred.
Part D
The four fundamental forces that operate in the universe today are:
Hint D.1
Study Section 23.1 (and see Section S4.2 for more detail)
ANSWER:

strong force, weak force, electric force, magnetic force. nuclear force, gravity, electric force, magnetic force. strong force, weak force, electromagnetic force, gravity. nuclear force, electromagnetic force, gravity, tidal force.
Part E
A "GUT" (grand unified theory) refers to theories that ______.
Hint E.1
Study Section 23.1
ANSWER:

unify gravity with the strong and weak forces. unify the electromagnetic and weak forces. unify all four forces together. unify the strong force with the electromagnetic and weak forces.
Part F
What do we mean by inflation?
Hint F.1
Study Section 23.1
ANSWER:

We mean the sudden release of photons when a particle and antiparticle annihilate one another We mean the expansion of the universe that we still observe today. We mean a sudden and rapid acceleration of the universe that went on for a tiny fraction of a second at the time the strong force froze out from the GUT force. We mean quantum fluctuations by high speed, relativistic particles in a state of false vacuum cause disturbances in the space-time continuum leading to the process described in the question to which this answer refers.
Part G
Of the statements below, which one correctly summarizes the events in the early universe according to the Big Bang theory?
Hint G.1
Study Section 23.1
ANSWER:

The universe began with the forces unified. During the first fraction of a second, the forces separated and there was a brief but important episode of inflation. Subatomic particles of both matter and antimatter then began to appear from the energy present in the universe. Most of the particles annihilated to make photons, but some became protons, neutrons, electrons, and neutrinos. The protons and neutrons underwent some fusion during the first three minutes, thereby determining the basic chemical composition of the universe. An episode of what we call inflation initiated the event of the Big Bang. Once the Big Bang got underway, particles and forces began to appear one by one. The forces produced protons, which fused to make hydrogen and helium until the universe was about 380,000 years old. Then gravity began to act, turning the hydrogen and helium into galaxies. The Big Bang began with the initiation of what we call inflation, which gradually slowed to the current expansion rate of the universe. Forces came to exist for a different reason, having to do with quantum fluctuations in the space-time continuum. Particles came to exist as a result of cracks made when forces froze. Once there were particles, gravity brought them together to make stars, and the stars then turned the particles into hydrogen, helium, and other elements. Forces and various subatomic particles began to appear during the first second after the Big Bang. For reasons not understood, the particles were all made of ordinary matter and none were made of antimatter, thus explaining why we live in a universe made of matter. The particles underwent some fusion for the first 380,000 years after the Big Bang, at which time the first stars were born.
Part H
Which statement about the cosmic microwave background is NOT true?
Hint H.1
Study Section 23.2
ANSWER:

It is the result of a mixture of radiation from many independent sources, such as stars and galaxies. Its spectrum corresponds to a temperature of just under 3 degrees above absolute zero. With the exception of very small variations, it appears essentially the same in all directions in which we look into space. It is thought to be radiation that began its journey to our telescopes when the universe was about 380,000 years old.
Part I
The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?
Hint I.1
Study Section 23.2
ANSWER:

(1) the theory predicts the existence of and the specific characteristics of the observed cosmic microwave background; (2) the theory correctly predicts the observed overall chemical composition of the universe. (1) the theory correctly predicts that the universe should be expanding; (2) the theory predicts the existence of and the specific characteristics of the observed cosmic microwave background (1) the theory correctly predicts that the universe should be expanding; (2) the theory correctly predicts the observed ratio of spiral to elliptical galaxies in the universe. (1) the theory predicts the episode of inflation that we think occurred in the early universe; (2) the theory predicts the existence of large quantities of dark matter.
Part J
Measuring the amount of deuterium in the universe allows us to set a limit on _______.
Hint J.1
Study Section 23.2
ANSWER:

the acceleration of the universe. the density of ordinary (baryonic) matter the universe. the current age of the universe. the total amount of mass in the universe.
Part K
Based on the Big Bang theory, what do observations of the cosmic microwave background and of chemical abundances in the universe suggest about dark matter?
Hint K.1
Study Section 23.2
ANSWER:

Dark matter was produced during the era of nuclei. Dark matter probably does not really exist. Much of the dark matter must be made of non-ordinary (nonbaryonic) matter, such as WIMPs. Dark matter must be made of MACHOs.
Part L
Which of the following observations cannot be explained by the Big Bang theory UNLESS we assume that an episode of inflation occurred?
Hint L.1
Study Section 23.3
ANSWER:

The fact that about 25% of the ordinary matter in the universe consists of helium. The fact that the temperature of the cosmic microwave background is almost the same everywhere. The fact that the universe is expanding. The existence of the cosmic microwave background.
Part M
The idea of inflation makes one clear prediction that, until quite recently, seemed to contradict the available observations. What is this prediction?
Hint M.1
Study Section 23.3
ANSWER:

The universe should be geometrically "flat" (in the four dimensions of spacetime). Inflation predicts that the temperature of the cosmic microwave background should be almost (but not exactly) the same everywhere. Inflation predicts that the entire universe must be far larger than the observable universe. Inflation predicts that the early universe should have regions of enhanced density that could have acted as "seeds" for the formation of galaxies and large structures.
Part N
Olber's Paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question?
Hint N.1
Study Section 23.4
ANSWER:

How many stars are in the universe? Can we measure the position and momentum of an electron at the same time? What would it be like to ride on a beam of light? Why is the sky dark at night?
Part O
What is the temperature of the universe today?
Hint O.1
Study Section 23.2
ANSWER:

3K 300K 3000K The universe cannot be said to have a single temperature.
Part P
Which of the four forces operate only over very tiny distances?
Hint P.1
Study Section 23.1
ANSWER:

Gravity Strong force. Weak and strong forces. Electromagnetic force.
Part Q
Arrange these states of matter in order of increasing temperature: atomic gas, molecular gas, ionized gas.
Hint Q.1
Study Section 23.1
ANSWER:

Molecular, ionized, atomic Molecular, atomic, ionized. Atomic, ionized, molecular Atomic, molecular, ionized Ionized, molecular, atomic Ionized, atomic, molecular
Part R
Which of the following statements cannot be tested by current scientific methods?
Hint R.1
Study Section 23.3
ANSWER:

The expansion of the universe is now accelerating. Prior to the Planck time, our universe sprouted from another universe. The universe is 14 billion years old. Our universe is flat.