What is the Cosmic Microwave Background, or CMB? The light emitted by the most distant stars. The radiation that was spread throughout the Universe at the time that it became transparent to light. The white lining of the microwave oven in your kitchen, made from metal found asteroids. The light emitted by dark matter that went undetected for nearly 100 years. QUESTION 23 The CMB fits almost perfectly to a blackbody curve of an object with a temperature of 2.73K. This means that The temperature of the early Universe was colder than 2.73K, because the Universe has warmed with time. The temperature of the early Universe was 2.73K. This means nothing, because the Universe isn’t a blackbody. That the CMB matches a blackbody curve is a coincidence. The temperature of the early Universe was much hotter than 2.73K, because the radiation has been significantly redshifted since it was emitted. QUESTION 24 Why was it important that the CMB is not perfectly uniform everywhere on the sky? Finding deformations disproved the theory of Inflation. There needed to be deformations in order for galaxies to be seeded in the later Universe. Finding deformations proved that it was impossible for locations on opposite sides of the Observable Universe to have ever been close enough to exchange information via light. Finding deformations disproved the Cosmological Principle.