Why is dark matter is inferred to exist?
Because we can observe its gravitational influence on visible matter
Dark energy has been hypothesized to exist in order to explain what?
Observations suggesting that the expansion of the universe is accelerating
The flat part of the Milky Way's rotation curve tells us that stars in the outskirts of the galaxy do what?
Orbit the galactic center just as fast as stars closer to the center
What is a likely candidate for the majority of the dark matter in galaxies?
Subatomic particles that we have not yet detected
The major evidence for the idea that the expansion of the universe is accelerating comes from the observations of what?
White dwarf supernoave
Is the universe hotter or cooler since the Big Bang?
It is cooler
What do the laws of thermal radiation tell us about objects and their wavelength?
Hotter objects emit light with shorter wavelengths (higher energy)
What important event occurred about 0.001 seconds after the Big Bang?
Most matter in the early universe was annihilated by antimatter
What was the first important event to occur in the history of the universe?
Spacetime rapidly expanded during a brief period of inflation
During the history of the universe, what event occurred 380,000 years after the Big Bang?
Light began to travel freely through the universe
When was the hydrogen nuclei in our universe created?
By the time our universe was about 3 minutes old
When were protons formed?
During the particle era
How is the cosmic microwave backward now compared to when it was first released?
Fainter and has most of its photons at longer wavelengths
If the era is older, is it hotter or cooler than a newer era?
The older the era, the hotter it is
Is an older era larger or smaller than a new era?
Older eras are smaller
What is the charge of an antiproton?
Negative
What happens when a proton collides with an antiproton?
They convert into two photons
What is the current temperature of the universe?
A few degrees
What does inflation help explain?
The uniformity of the cosmic microwave background and the origin of galaxies
What is the best explanation for why the sky is dark?
Because the universe is not infinite in space