EVOLUTION OF UNIVERSE

 EVOLUTION OF UNIVERSE

                        World scientist James Pebbles won the 2019 Nobel Prize in Physics for his contributions to the theory of the origin and evolution of our universe.  In this article, he describes the ideas he co-authored with Scientific American in 1994.

 At a particular moment about 15 billion years ago, all the matter and energy we could see, concentrated in a region smaller than a penny, began to expand and cool at an astonishingly fast rate.  The forces of nature assumed their current properties until the temperature of the Sun's core dropped 100 million times, and the elementary particles, known as quarks, were moving freely in the ocean of energy.  When the universe expanded 1.0 times, the size of the solar system was filled with everything we could count on.

 At that time the free quark was trapped in neutrons and protons.  As the universe grew by another factor of 1.0, protons and neutrons came together to form the nucleus, which contains most of the helium and deuterium that exist today.  It all happened within the first minute of the extension.  However, the conditions were still too hot for the nuclei to capture electrons.  Only after this expansion continued for 300,000 years did neutral atoms appear in abundance, and the universe became 1,000 times smaller than it is now.  The neutral atoms then began to mix with the gas clouds, which then evolved into stars.  By the time the universe had expanded to one-fifth of its current size, the stars had formed groups known as young galaxies.

When the size of the universe was less than half of its current size, the atomic reactions in the stars formed most of the heavy elements from which the terrestrial planets were formed.  Our solar system is relatively young: it was formed five billion years ago, when the universe was two-thirds of its current size.  Over time, the formation of stars has reduced the supply of air in galaxies, and as a result, the population of stars has been declining.  Fifteen billion years from now, stars like our Sun will be relatively rare, making the universe a much less hospitable place for observers like us.

 Our understanding of the origin and evolution of the universe is one of the great achievements of twentieth century science.  This knowledge comes from decades of innovative experiments and theories.  Modern telescopes on Earth and in space search for light from galaxies billions of light-years away and show us what the world looked like when we were young.  Particle accelerators investigate the basic physics of the high-energy atmosphere of the early universe.  

            

       Explore the remaining global background radiation from the early stages of satellite expansion, providing the largest image of the universe we can observe.

 Our best efforts to explain this wealth of data have been embodied in a theory known as the Standard Cosmology Model or the Big Bang Cosmology.  

        The main claim of this theory is that the universe is expanding in a massive average, almost homogeneously from the very beginning.  At present, there are no fundamental challenges to the Big Bang theory, although there are certainly unresolved issues in the theory itself.  For example, astronomers are not sure how galaxies formed, but there is no reason to believe that this process did not take place in the frame of a big bang.  Indeed, the predictions of the theory have survived all the tests to date.

 Yet the Big Bang model only goes so far, and many basic secrets still remain.  How did it happen before the universe expanded?  (You can't look back beyond the moment any of the observations you made began to expand.) What will happen in the distant future when the last stars run out of fuel?  No one knows the answers yet.

 Our universe may have been seen by many mystics, philosophers, philosophers or scientists in many lamps.