Why Is the Cosmic Microwave Background (CMB) So Cold If

question 32

Multiple Choice

Why is the cosmic microwave background (CMB) so cold if the early universe was so hot?

• A) Enough time has passed for matter in the universe to release enough heat to cool down.
• B) The CMB constantly interacts with atoms, which effectively cool down the photons.
• C) The expansion of the universe has redshifted those photons to an effectively cooler temperature.
• D) Misleading; The Big Bang was initially hot but the CMB was released from cold material much later on.

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Definitions:

Predictor Variables

Independent variables used in regression analyses to predict or explain variations in the dependent variable.

Linear Regression

Statistical procedure in which a straight line is fitted to a set of data to best represent the relationship between two variables.

Multiple Correlation

A statistical technique that measures the strength of a relationship between one dependent variable and two or more independent variables.

Correlation

A statistical measure that expresses the extent to which two variables change together, and thus how well one variable predicts the other.