PT159.S2.P3.Q20 > Analytics

Hide analysis

Since 1929, cosmologists have known that the universe is expanding. █████ █████████ ████ ███████ ████ ███ █████████ ██ ███████ ██ ███ ██████████ ███ ███████ ████ ███████ ███ ██ ███ ████ ██████ ███████████ ███ ███ ██ ███████ ███ ███████ ██ █████████ ███ █████████ ██ █████████ █████ █████ ██ ███████████ ██ █████ █████████ ███ ████████ ██████████ ████ ████ ████ ███████ ████ █████████ █████ ████████ █████ ████ ███ █████████ ██ ███ ████████ ██ ████████ █████████████

Unexpected phenomenon · Expansion of universe is accelerating, rather than slowing down

████████████ ████ ████████ ███ ████████████ ███ ███ ███████████ █████████ ██ ███ █████████ ████ ███ █ █████████ ██ ███ ███████ ██████████ ██ ███ █████████ ███

Two potential explanations · Both challenge current understanding of the universe

███ █████ ███ ████ ██████ ████████ ██████ ██████ █ ████ ██ █████ ███████ ████ ██████ █████ ██████ ██ ████████ ██████ ███████ ██ ███ █████████ ██ ███ ███ ████ ████ █████████ ███ ████ ███ ████ ███████ ██████████ ████ ██ █████ ████ ███████ ███ █ ████████ ███ ██████ ██ ███ ██████████ █████████ ███ ████████ ███████ ██ ███ ████ ██████ ██████ ██████████ ████ ████ ██████ ██ ██ ████████ ████ ██ ███ ██████ ██ ██████ ███ ████ ██ ██████ █ ████████ █████████ ███ █████ ██████ █████ ████ ██ █████ ████ ████████ ████████ ████ █ ████████ ██ █████████ █████ ██ ███████ ███ █████████████ ██████████ ██ █████ ██ ███████ ███ ███ ████████ ██ ███ █████████ █████ ███ ███ ████████ ██ █████ █████████ ███ ██████ ██ ███████████ ████ ███████████ █████ ████ ███ ████████ ██ ██ ████ ██████████ ███ ██████████ ████████ ████ ███ ██ ████ █████ ██ ████ ██████ ███ █████████████

Explanation 1 · Dark energy

The idea of energy stretching space dates back to Einstein. There’s some support for this theory.

Potential origin of dark energy · Created by “virtual” particles

The particles pop in and out of existence, creating “vacuum” energy.

██████████████ ████████ █████ ██ █ █████ ███████████ ███████ ███ █████████ █████ ██ ███ ██████ ██████ ███ ███ ██████ ██ ██████ ██████ ██ ███████ ███ ███████████ ██████████

Inconsistent evidence · “Vacuum” energy theory of dark energy not supported

Explanation 2 · Gravity doesn’t work as predicted across large distances

Additional details about Explanation 2 · Theory is radical and might be easier to test than dark energy theory

Passage Style

Phenomenon-hypothesis (RC)

20.

It can be inferred from ███ ███████ ████ ███ ██████ █████ ██ ████ ██████ ██ █████ ████ █████ ███ ██ ███ █████████ ███████████

Physicists can use █████ ████████████ ██ █████████ ██ ███ █████ ██████ ██ █████████ ███████ ██████████ ███████ ██████ ██ ██████████ █████████ ████████ ███ ███ ███████ ██████

Supported. We're told that the second theory, which questions the gravitational predictions of the theory of relativity, can be tested in our own solar system.

58%

From 1929 until ███ ████ ██████ ███████████ ████████ ████ ███ ████████ ███ █████ ██ █████

Anti-supported. Astronomers believed the universe was expanding, but thought that the rate of expansion was decreasing rather than increasing.

Particle physicists originally ██████████ ███ █████████ ██ ███████ █████████ ██ █████ ██ ███████ ████ ███████

Not supported. We don't know why particle physicists originally postulated virtual particles. Dark energy theorists believe the virtual particles are relevant to dark energy, but this doesn't imply that the particle physicists had dark energy theory in mind when they first came up with virtual particles.

15%

The best available ████████ ████████ ████ ██████████ ███████ ██████ ██ ██████████ █████ █████████ ███████████ █████ ███████ ██████ ████ █████ ██████████

Not supported. The idea that Einstein's theory of relativity makes wrong predictions about gravity across very large distances is the second theory described in the last paragraph. But the author never indicates that the best available evidence supports this theory. Rather, the author notes that this theory is easier to test than the dark energy theory. But this doesn't tell us what existing evidence supports.

12%

Einstein proposed the ████████████ ████████ ██ █████ ██ ████████ ███ ████████ ██████ ██████ ███████ ██ ███████ ██████████

We're told Einstein proposed the cosmological constant to explain why the universe isn't shrinking under its own gravity. This constant was designed to describe some type of pressure that keeps the universe from shrinking. But we don't know that Einstein was even aware of the theory of vacuum energy or that virtual particles might create vacuum energy. So it wouldn't make sense to say that Einstein proposed the cosmological constant to describe the pressure from virtual particles.

13%

PrepTest 159 - Section 2 - Passage 3 - Question 20

Difficulty

Analysis

Answer Popularity

Question history

Confirm action