Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
Welcome to our Physics lesson on The Subatomic Era, this is the second lesson of our suite of physics lessons covering the topic of Chronology of the Universe, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
In the first instants after the Big Bang, Space was occupied by a plasma consisting of a number of very strange particles. It is impossible today to obtain these particles artificially in laboratories because of their extremely high temperature and energy. All these particles were creating and disappearing together with their corresponding antiparticles after colliding with each other at high energies. At these instants of the Universe existence known as the subatomic era, the values of energies exchanged were much higher than 1 GeV - the energy necessary for the quarks binding in nucleons. Hence, it was impossible to make quarks bind with each other to obtain the elementary particles necessary for the nuclei formation. Every casual binding of this kind would immediately cease to exist because of the strong collision between the particles involved. When the Universe eventually cooled down, the average thermal energy of collisions decreases and photons lost some of their energy. Therefore, all particles and antiparticles involved in interaction processes given by the relations
that occurred at the first instants after the Big Bang, became lighter with time.
With the decrease in temperature, a phenomenon known as the number of particles freeze which depended on the inability of the Universe to realize both of the above reactions but only the second one. As a result, an equal number of particles and antiparticles involved in such a reaction results in the annihilation of both of them and in the generation of two high-energy photons. Since photons are considered as particles (from the matter-energy equivalence), it is obvious that there are more particles than antiparticles in the Universe.
The thermal energy of quarks necessary to form nucleons (protons and neutrons) is 1 GeV. How long after the Big Bang were nucleons formed in the Universe?
Given the relationship between time elapsed since Big Bang and energy of matter in the Universe,
we obtain for the instant of nucleons formation in the Universe
Thus, nucleons have started to form 1 microsecond after the Big Bang.
You have reached the end of Physics lesson 22.11.2 The Subatomic Era. There are 6 lessons in this physics tutorial covering Chronology of the Universe, you can access all the lessons from this tutorial below.
Enjoy the "The Subatomic Era" physics lesson? People who liked the "Chronology of the Universe lesson found the following resources useful:
Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
We hope you found this Physics lesson "Chronology of the Universe" useful. If you did it would be great if you could spare the time to rate this physics lesson (simply click on the number of stars that match your assessment of this physics learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of physics and other disciplines.