What parameters describe the universe?

Historically, the main unknown that scientists try to solve is the model of the universe. Physics professor Lyman Page has now explained in his book, “The Little Book of Cosmology,” published by Princeton University Pressthat said model based on six parametersas collected BBC.

Universe

What does the universe contain?

The The first three explain to us what the universe contains: Matter and energy. Of these, the first is responsible for describing the number of atoms in the cosmos, which constitutes only 5% of the universe. In second place is the one that studies dark matter, a type of matter that is still unknown and that corresponds to 25% of the universe.

In this sense, explains Page, the amount of dark matterwhich can be resolved by measurements of the small temperature fluctuations of the microwave background (CMB) radiation, agrees with the value that is obtained of the observations of the motions of stars and galaxiesalthough the value found with the CMB is much more accurate.

The microwave background radiation also reveals something else, and that is that, as they are waves that reach us from the decoupling, when the early universe reached a temperature cold enough that it released the hot plasma photons that had linked them for thousands of years. after the Big Bang, dark matter existed already then. In addition, it is also possible to determine that the atoms make up only one sixth of the total mass of the universe.

cosmological constant

The cosmological constantthe dark energy that is at the origin of the rapid expansion of the universe, is the third parameter. It represents 70% of the total matter and energy in the universe and we don’t know exactly what it is, although we are able to measure it through cosmic acceleration, Page details.

Optical depth

The next parameter is the optical depthwho studies how opaque was the cosmos for the photons that move in it, that is, it includes the little knowledge we have about the complex process of formation and birth of the first stars, as well as the creation of the first galaxies in the universe.

The light that these gave off decomposed the hydrogen that was still in the cosmos, leaving only its protons and electrons and causing the reionization of the universe. During this process, between 5% and 8% of the CMB photons, which had been released in decoupling, were scattered again.

“To use an analogy, considering that the universe had previously been transparent, it’s as if a little fog had entered. Not too much, you could still see a distant shore, but the visibility was reduced. Interestingly, to determine the optical depth of the universe, a measurement of the polarization of the CMB is taken.”exemplifies the astrophysicist.

Small changes that originated the current structure

As for the last two parametersare responsible for explaining the small changes that originated the current structure that the universe presents. One of these is known as the primordial power spectrum, and it describes fluctuations in density in three-dimensional space.

In the very early universe, the fluctuations were small, but they grew large throughout the cosmos as the universe expanded. So where did they exist? slightly denser areascan now be seen galaxies or clusters of galaxieswhile in those with less density, now practically nothing can be seen.

Finally, the remaining parameter is the scalar spectral index. This is the most complicated parameter, since it constitutes the best element to study the origin of the universesince it studies how the first energy changes of the early universe depend on the angular scale.

To better understand this, let’s use a music analogy. This last cosmological parameter allows us to distinguish between ‘White noise’ and, let’s say, ‘pink noise’, in which the low notes (analogous to the large angular scales) are somewhat louder than the high notes (analogous to the small angular scales)»Page explains.

As well, “Using the CMB, we found that the primordial fluctuations were slightly larger in amplitude on large angular scales than on smaller ones”namely, “primordial cosmic noise is slightly pink”.

Font: 20 minutes

Reference article: https://www.20minutos.es/noticia/4563210/0/parametros-describen-universo/?autoref=true