What Was the Temperature of the Universe When Photons Were

question 52

Essay

What was the temperature of the universe when photons were no longer able to spontaneously create proton-antiproton pairs? (Note that a photon's energy is equal to , the cosmic background at any point in time has a blackbody spectrum that peaks at a wavelength , and the mass of a single proton is 1.67*10^-27 kg.)

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Definitions:

Positive Predictive Value

The probability that individuals with a positive test result actually have the disease.

Specificity

The ability of a test to correctly identify those without the disease or condition being tested for.

Positive Predictive Value

The probability that subjects with a positive screening test truly have the disease.

Prevalence

The total number of cases of a disease that exist in a particular population at a specific time.