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.
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
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.
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 explains why the night sky is dark?
The universe has a finite age.
Which statement can NOT be tested by science today?
Prior to the Planck time, our universe emerged from another universe.
When a proton and an antiproton collide, they
convert into two photons.
During the history of the universe, what important event occurred about 0.001 seconds after the Big Bang?
Most matter in the early universe was annihilated by antimatter.
Which of the following important events occurred earliest in the history of the universe?
Spacetime 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 was 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
The current temperature of the universe as a whole is
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
When the universe was 380,000 years old, its thermal radiation spectrum consisted mostly of
visible and infrared photons.
Which of the following does inflation help to explain?
the uniformity of the cosmic microwave background
Which of these pieces of evidence supports the idea that inflation really happened?
observations of the cosmic microwave background that indicate a flat geometry for the universe
What is the earliest time in the universe that we can directly observe?
a few hundred thousand years after the Big Bang
Which of these options is the best explanation for why the night sky is dark?
The universe is not infinite in space.
