Chapter 17

What happens when a particle of matter meets its corresponding antiparticle of antimatter? The combined mass of the two particles is completely transformed into energy (photons). They can form a complete atom. They fuse to make a heavier particle. The question makes no sense, since antimatter does not really exist.

What happens to gas as it freely expands? It gets more dense and heats. It gets more dense and cools. It gets less dense and cools. It gets less dense and heats.

A "GUT" (grand unified theory) refers to theories that _________. unify all four fundamental forces together unify the strong force with the electromagnetic and weak nuclear forces unify the electromagnetic and weak nuclear forces unify gravity with the strong and weak nuclear forces

What do we mean by inflation? the expansion of the universe that we still observe today the sudden release of photons when a particle and antiparticle annihilate one another a sudden and extremely rapid expansion of the universe that occurred in a tiny fraction of a second during the universe's first second of existence the increase in costs of doing cosmological observations

Which statement about the cosmic microwave background is NOT true? Its spectrum corresponds to a temperature of just under 3 degrees above absolute zero. It is the result of a mixture of radiation from many independent sources, such as stars and galaxies. It is thought to be radiation that began its journey to our telescopes when the universe was about 380,000 years old. With the exception of very small variations, it appears essentially the same in all directions in which we look into space.

In the past, the temperature of the universe was _____. hotter than it is today 3 K absolute zero (0 K) cooler than it is today

The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they? (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 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 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. (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 primeval universe.

Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred? the existence of the cosmic microwave background the fact that nearly all of the stars in the universe consists of about 25% helium and 75% hydrogen (with trace amounts of heavier elements) the fact that the universe is expanding the fact that the temperature of the cosmic microwave background is almost the same everywhere

Which of the following statements can NOT be tested by science today? The expansion of the universe is now accelerating. Our universe is flat. Prior to the Planck time, our universe emerged from another universe. The universe is 14 billion years old.

Which of the following statements explains why the night sky is dark? The universe has an edge, beyond which there are no stars. The universe is full of dark matter. The universe has dust that blocks the light from distant galaxies. The universe has a finite age.