Cosmic timeline 06
In our Cosmic timeline we are about to leave the electroweak epoch.
In physical cosmology the electroweak epoch was the period in the evolution of the early universe when the temperature of the universe was high enough to merge electromagnetism and the weak interaction into a single electroweak interaction (> 100 GeV).
As we have seen before, the electroweak epoch began approximately 10-36 seconds after the Big Bang, when the strong force separated from the electroweak interaction. It was this phase transition that triggered a period of rapid and exponential expansion known as cosmic inflation.
At approximately 10-32 seconds after the Big Bang the potential energy of the inflaton (the particle identified with this inflation) field that had driven the inflation of the universe during the inflationary epoch was released, filling the universe with a dense, hot quark-gluon plasma. Particle interactions in this phase were energetic enough to create large numbers of exotic particles, including W and Z bosons and Higgs bosons.
What is a quark?
The scientists thinking about how the universe began, how it was shaped and defined in this Big Bang, have imagined, and worked out from their theories the existence of weird and wonderful new particles. The quark is one of these newly identified particles. Quarks appear in three generations. The first generation includes up and down quarks, the second charm and strange quarks, and the third top and bottom quarks.
This strange use of language goes with the need to give names and qualities to new kinds of physical matter. The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig. It was Murray Gell-Mann who named quarks quarks!
Gell-Mann originally named the quark after the sound made by ducks. For some time, he was undecided on an the actual spelling for the term he intended to coin, until he found the word quark in James Joyce’s book Finnegans Wake:
Three quarks for Muster Mark!
Sure he has not got much of a bark
And sure any he has it’s all beside the mark.
—James Joyce, Finnegans Wake
As Murray Gell-Mann mention in his book The Quark and the Jaguar there is the dream of a publican named Humphrey Chimpden Earwicker.
“Words in the text are typically drawn from several sources at once, like the “portmanteau” words in “Through the Looking-Glass”. From time to time, phrases occur in the book that are partially determined by calls for drinks at the bar. I argued, therefore, that perhaps one of the multiple sources of the cry “Three quarks for Muster Mark” might be “Three quarts for Mister Mark”, in which case the pronunciation “kwork” would not be totally unjustified. In any case, the number three fitted perfectly the way quarks occur in nature.”
Photograph of the event that led to the discovery of the Σ
baryon, at the Brookhaven National Laboratory in 1974.
As the universe expanded and cooled, interactions became less energetic and when the universe was about 10-12 seconds old, W and Z bosons ceased to be created. The remaining W and Z bosons decayed quickly, and the weak interaction became a short-range force in the following quark epoch.
This is a picture of the quark gluon plasma. Here the coloured constituents are able to move freely within the blob of heated, deconfined matter. The initial temperature of the fireball which creates such extreme conditions is some hundred MeV. That is about 1013 Kelvin, a pretty hot soup.
This is hadronic matter: where the grey bubbles indicate the colour-neutral hadrons, inside which you see the valence quarks (large) and further virtual colored particles – so called sea quarks, and gluons. The arrows indicate the isospin of the quarks. The protons and neutrons consist of up and down quarks, with isospin +1/2 (up quark), and isospin -1/2 (down quark), respectively.
A new epoch is about to begin – the hadron epoch!
At about 0.000000000000000000000000000000000001 seconds into the Big Bang the inflationary phase transition ends and radiation and matter are created.
So, after cosmic inflation ends, the universe is filled with a quark-gluon plasma. From this point onwards the physics of the early universe is better understood, and less speculative.
In physical cosmology the quark epoch was the period in the evolution of the early universe when the fundamental interactions of gravitation, electromagnetism, the strong interaction and the weak interaction had taken their present forms, but the temperature of the universe was still too high to allow quarks to bind together to form hadrons. The quark epoch began approximately 10-12 seconds after the Big Bang, when the preceding electroweak epoch ended as the electroweak interaction separated into the weak interaction and electromagnetism.
During the quark epoch the universe was filled with a dense, hot quark-gluon plasma, containing quarks, leptons and their antiparticles. Collisions between particles were too energetic to allow quarks to combine into mesons or baryons.
The quark epoch begins at 1 pico second and ended when the universe was about 10-6 seconds old when the average energy of particle interactions had fallen below the binding energy of hadrons. The following period, when quarks became confined within hadrons, is known as the hadron epoch.