Question

why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions? group of answer choices the overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form. the overall structure of the universe is very uniform, but intervening gas between us and the era of nuclei absorbs wavelengths depending on the composition and redshift of the gas. the temperature of the universe can be found by taking an average over the entire sky, but individual stars will create peaks in the temperature over small angles. the overall structure of the universe is very uniform, but the synthesis of different elements produces varying signatures within the background radiation.

Answer 1

The cosmic microwave background (CMB) is expected to be almost uniform because the early universe had an almost smooth structure.

However, slight fluctuations were present that later allowed for the growth of galaxies and other structures. These small density variations are evident through the slight temperature differences observed in the CMB.

Therefore, the correct answer is: option "the overall structure of the universe is very uniform".

Step-by-step explanation:

At the time of decoupling, when the CMB was emitted, tiny fluctuations in density existed. These fluctuations, while small, were significant enough that over time, they allowed matter to concentrate under gravity and form large-scale structures like galaxies and galaxy clusters.

Had the early universe been perfectly uniform, the gravitational pull would have been inadequate for the formation of such structures. Moreover, the CMB displays slight temperature variations which provide evidence of these density variations, and are the seeds from which cosmic structures grew.

Observations show that the temperature of the CMB varies slightly, indicating small differences in density. These are the wrinkles in the CMB that signal the early stage fluctuations necessary for star and galaxy formation.

If the universe was perfectly smooth, the lack of gravitational pull near those primordial fluctuations would have prevented the formation of galaxies. The CMB fluctuations we observe today are the remnants of those early density differences that were crucial for structure formation in the universe.