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

question 7

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 cools down the photons.
• C) The big bang was initially hot but the CMB was released from cold material much later on.
• D) The expansion of the universe has redshifted those photons to an effectively cooler temperature.

---

Definitions:

Linkage Disequilibrium

The non-random association of alleles at two or more loci, not necessarily on the same chromosome, which can influence genetic traits and disease risks.

Physical Linkage

The adjacency of two or more loci on the same chromosome.

Genetic Recombination

The exchange of genetic material between paired chromosomes during meiosis. Recombination can form new combinations of alleles and is a source of heritable variation.

Heritability

A measure of how much of the variation in a trait within a population is due to genetic differences among individuals in that population.