Question

What is meant by matter-radiation crossover? The conversion of matter into radiation by E = mc^2. The conversion of radiation into mass by E = mc^2. The time in the early universe when the radiation density had decreased relative to the matter density until they were equal. The time in the early universe when the matter density had decreased relative to the radiation density until they were equal. The special time in the present universe when the matter density is approximately equal to the dark radiation density. The diagram to the right is a sketch of two blackbody curves. Which of the following statements is true? Blackbody A is denser than blackbody B Blackbody B is denser than blackbody A. Blackbody A is hotter than blackbody B. Blackbody B is hotter than blackbody A. It is impossible to determine anything about temperature or density from blackbody curves.

Answer 1

Solution: (5)In early Universe, after the Big Bang, the universe is radiation dominated Most of the energy of the Universe is radi ation dominated. As time passes, the Universe starts to become cool. Then the Universe entered the mass dominated era. Hence the time in the early universe when the radiation den sity had decreased relative to the matter density until they are equal