The standard model of cosmology combines observations of the expanding universe, the cosmic microwave background, and the abundance of light elements. It also leads to a surprising conclusion: most of the universe is not made of familiar matter.
The standard model of cosmology, also called the concordance model, is the simplest model that explains a wide range of observations. It assumes that general relativity correctly describes gravity on cosmic scales. The model accounts for the existence and structure of the cosmic microwave background (CMB), the observed abundances of light elements, and the accelerated expansion of the universe.
All flashcards
What is the standard model of cosmology?
The concordance model: a model using general relativity to explain observations including the CMB, light-element abundances, and accelerated expansion.
What is critical density?
The density associated with a spatially flat universe in the standard cosmological model.
Why does deuterium abundance constrain ordinary matter?
Measurements of deuterium limit ordinary matter to about 5% of critical density.
What is a WIMP?
A hypothetical massive elementary particle that interacts only weakly with ordinary matter.
How can a WIMP collision appear in a direct-detection experiment?
It may cause a tiny vibration, a small temperature increase, or a flash of light.
Quiz questions
Why can ordinary dark objects such as planets or black holes not account for all the dark matter?Answer: Ordinary matter is limited to about 5% of critical density, while dark matter is about 27%.
Why are direct-detection experiments often placed deep underground?Answer: Rock shields the detectors from cosmic rays and other unwanted particles.
What does missing energy at a particle collider suggest in a dark matter search?Answer: An invisible particle may have carried energy away from the collision.
Why are WIMPs difficult to detect directly?Answer: Their weak interactions make collisions with ordinary matter rare.
How could dark matter help ordinary matter form early galaxies?Answer: Dark matter concentrations formed gravitational wells into which ordinary matter could later fall.
Based on Astronomy 2e by Andrew Fraknoi, David Morrison, Sidney Wolff (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.