Which of the following is an important starting assumption in models of galaxy formation?
Some regions in the universe start out denser than others.
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).
What happens to gas as it freely expands?
It gets less dense and cools.
A "GUT" (grand unified theory) refers to theories that _________.
unify the strong force with the electromagnetic and weak nuclear forces
What do we mean by inflation?
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
When a proton and an antiproton collide, they
convert into two photons.
The charge of an antiproton is
negative
Although we can divide the history of the universe into many distinct "eras," sometimes it's useful just to have a broad perspective on what events occurred in the very early universe and what events occurred later. Listed following are events that occurred either before or after the first five minutes in the history of the universe. Match these events to the appropriate time period.
Within the first five minutes
*antielectrons (positrons) as common as electrons
*temperature fell to 10^15K
*strong force and electroweak force first became distinct
*inflation occured
Sometime after the first five minutes
*galaxies formed
*photos of cosmic microwave
*stars formed
*carbon nuclei formed by fusion
During the history of the universe, what important event occurred about 0.001 seconds after the Big Bang?
Most matter was annihilated by antimatter.
Which of the following important events occurred earliest in the history of the universe?
Space-time rapidly expanded during a brief period of inflation.
During the history of the universe, what important event occurred about 380,000 years after the Big Bang?
Light began to travel freely through the universe.
Essentially all the hydrogen nuclei that will ever exist in our universe were created __________.
by the time the universe was about 3 minutes old
Compared to when the cosmic microwave background was first released, the radiation of the cosmic microwave background today is __________.
fainter and has most of its photons at longer wavelengths
Which statement about the cosmic microwave background is NOT true?
It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
In the past, the temperature of the universe was _____.
hotter 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 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.
What is the current temperature of the universe?
a few K
Which of the following does not provide strong evidence for the Big Bang theory?
observations of the amount of hydrogen in the universe
What is the earliest time from which we observe light in the universe?
a few hundred thousand years after the Big Bang
Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred?
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?
Prior to the Planck time, our universe emerged from another universe.
Which of the following does inflation help to explain?
the uniformity of the cosmic microwave background
Which of the following does inflation help to explain?
the origin of galaxies
Which of these pieces of evidence supports the idea that inflation really happened?
the apparently "flat" geometry of the universe
Which of the following best explains why the night sky is dark?
The universe is not infinite in space.
Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.
CONTINUED
A _____ predicts that the strong, weak, and electromagnetic forces should become indistinguishable at high temperatures
grand unified theory
The ______ is a single force that unifies the electromagnetic and weak forces.
electroweak force
______ was a dramatic expansion of the universe thought to have occurred when the universe was only a tiny fraction of a second old.
inflation
________ forces us to think about why the sky is dark at night.
oblers' paradox
Observations of the _____ provide a way to test our theory of the Big Bang.
cosmic microwave background
When a particle of ordinary matter meets its precise opposite particle of antimatter, the result is _______ with complete conversion of mass into energy.
annihilation
