The Big Bang, Nucleosynthesis, and the Formation of Structure

If the universe is expanding, it had to be smaller in the past.

What are the implications of this logic?

The Big Bang Model (movie)

• everything emerged from a tiny, dense dot (singularity) of energy and matter that unfolded into Universe we see now

• evidence...
  • galaxies are expanding away from each other (The Hubble Relation)

    The Hubble Relation. Linear relationship between distance and recession ``velocity", distance = ``velocity"/H0.

  • abundance of lightest elements can be explained by fusion in Universe when it was young, hot, and dense like star (Big Bang Nucleosynthesis)

    

    In the Beginning there was Nothing And then Big Bang! The Cosmic soup expanded and cooled the particle zoo was born in the goo photons, bosons, gluons, gravitons Energy radiation-Watch Out! Inflation!

    Superstrings wiggling in space-time Temperatures drop and the forces divide. Up, down, bottom, top, charmed and strange quarks stick together with glueball and chain to form protons and neutrons, mesons and leptons baryons and anyons and on and on and on?

    Gravity attracts and galaxies form. Stars burn up and the elements are born: Hydrogen, Helium, Lithium, Beryllium, Boron, Carbon Nitrogen, Oxygen, Fluorine, Sodium, Magnesium, Aluminum, and Silicon and on and on and on!

    These are the things that everything is made of chemical, mineral, vegetable and animal! Big Bang!             --Lynda Williams

    For a movie of Big Bang nucleosynthesis, click here.

    For more info, click here.

    • in 1950's and 60's, predominant theory regarding formation of chemical elements in Universe postulated that all elements produced either in star interiors or during supernova explosions

    • helium abundance problem: theory estimated that only 1-4% of all matter in Universe consisted of helium if stellar nuclear reactions only source of production, but upwards of 25% of Universe's total matter consists of helium

    • pioneering efforts of Russian physicist George Gamow and his collaborators led to modification of theory: high density and hot temperature of early Big Bang could produce helium via fusion

      

      • elements heavier than lithium originate in interiors of stars relatively late in Universe's history

      • light elements (deuterium, helium, and lithium) produced in first few minutes of Big Bang

        

        

        Thanks to J. Mohr for the above.

        • in first seconds of the Universe, temperature was billions of degrees, too hot for nuclei to stick together, hot broth of radiation and particles, size of Sun!

        • roughly three minutes after Big Bang, temperature of Universe rapidly cooled from its phenomenal 10³² Kelvin to approximately 10⁹ Kelvin, allowing nucleosynthesis, or the production of light elements, to occur

          

        • in short time interval, protons and neutrons collided to produce deuterium (one proton bound to one neutron), deuterium then collided with other protons and neutrons to produce helium and small amount of tritium (one proton and two neutrons)

        • about 98% of helium present in Universe today was produced not in stars, but in first few minutes of Big Bang

        • after next half hour (when lithium 7 was created), Universe cooled and expanded to point where fusion of heavier elements impossible

        • one value of baryon density in the early Universe can explain all the observed abundances at once -- theory works!

          

          Thanks to J. Mohr for the above.

  • space is filled with radiation from early hot phase, now diluted and reduced in energy via expansion to level of microwaves (Cosmic Microwave Background)

    

    Penzias and Wilson, Discoverers of 3 Degree Background Radiation (or Cosmic Microwave Background Radiation)

    • thermal spectrum corresponding to temperature of 2.7 K

      

      

    • radiation is mostly isotropic -- what small fluctuations there are led to formation of structure (galaxies, you, etc), see below

To read more about tests of Big Bang theory, click here.

If the Universe was this perfectly glowing ball of hot plasma, how does the structure we see today arise?

Starts like this...

and ends like this...

Can tiny fluctuations in the microwave background grow into galaxies and more? Use simulations (movie) and compare results of different models...