(A) The Vacuum: Its Fluctuations and Decay
(B) The Vacuum: Its Creation and Instability
(C) The Vacuum: A State of Absence
(D) Particles That Materialize in the Vacuum
(E) Classical Physics and the Vacuum
18. According to the passage, the assumption that the introduction of a real particle into a vacuum raises the total energy of that region of space has been cast into doubt by which of the following?
(A) Findings from laboratory experiments
(B) Findings from observational field experiments
(C) Accidental observations made during other experiments
(D) Discovery of several erroneous propositions in accepted theories
(E) Predictions based on theoretical work
19. It can be inferred from the passage that scientists are currently making efforts to observe which of the following events?
(A) The decay of a vacuum in the presence of virtual particles
(B) The decay of a vacuum next to a superheavy atomic nucleus
(C) The creation of a superheavy atomic nucleus next to an intense electric field
(D) The creation of a virtual electron and a virtual positron as a result of fluctuations of a vacuum
(E) The creation of a charged vacuum in which only real electrons can be created in the vacuum’s region of space
20. Physicists’ recent investigations of the decay of the vacuum, as described in the passage, most closely resemble which of the following hypothetical events in other disciplines?
(A) On the basis of data gathered in a carefully controlled laboratory experiment, a chemist predicts and then demonstrates the physical properties of a newly synthesized polymer.
(B) On the basis of manipulations of macroeconomic theory, an economist predicts that, contrary to accepted economic theory, inflation and unemployment will both decline under conditions of rapid economic growth.
(C) On the basis of a rereading of the texts of Jane Austen’s novels, a literary critic suggests that, contrary to accepted literary interpretations. Austen’s plots were actually metaphors for political events in early nineteenth-century England.
(D) On the basis of data gathered in carefully planned observations of several species of birds, a biologist proposes a modification in the accepted theory of interspecies competition.
(E) On the basis of a study of observations incidentally recorded in ethnographers’ descriptions of non-Western societies, an anthropologist proposes a new theory of kinship relations.
21. According to the passage, the author considers the reduction of energy in an empty region of space to which a real particle has been added to be
(A) a well-known process
(B) a frequent occurrence
(C) a fleeting aberration
(D) an unimportant event
(E) an unexpected outcome
22. According to the passage, virtual particles differ from real particles in which of the following ways?
I. Virtual particles have extremely short lifetimes.
II. Virtual particles are created in an intense electric field.
III. Virtual particles cannot be detected directly.
(A) I only
(B) II only
(C) III only
(D) I and II only
(E) I and III only
23. The author’s assertions concerning the conditions that lead to the decay of the vacuum would be most weakened if which of the following occurred?
(A) Scientists created an electric field next to a vacuum, but found that the electric field was not intense enough to create a charged vacuum.
(B) Scientists assembled a superheavy atomic nucleus next to a vacuum, but found that no virtual particles were created in the vacuum’s region of space.
(C) Scientists assembled a superheavy atomic nucleus next to a vacuum, but found that they could not then detect any real particles in the vacuum’s region of space.
(D) Scientists introduced a virtual electron and a virtual positron into a vacuum’s region of space, but found that the vacuum did not then fluctuate.
(E) Scientists introduced a real electron and a real positron into a vacuum’s region of space, but found that the total energy of the space increased by the energy equivalent of the mass of the particles.
