What evidence is there for the origins of the elements?

• Atoms are essential for understanding chemistry, biology, and geology
• Atoms did not always exist; they formed under specific conditions
• First atoms formed about 13.82 billion years ago, 380,000 years after the universe began
• Understanding the origin of atoms requires understanding the early universe
• Big Bang theory


  Explains the universe's origin and development
• The Big Bang model is based on decades of scientific work but has unresolved questions and alternative interpretations
• The universe started from a singularity and has been expanding for nearly 14 billion years
• The Big Bang was not a typical explosion; there was no matter, space, or time initially
• Emergence of matter, space, and time from the Big Bang is challenging to comprehend
• Key questions


  • The meaning of time beginning
  • The location of the Big Bang without pre-existing space
  • The origin of the initial energy
• Scientific exploration often leads to more questions, pushing the limits of understanding
• These inquiries extend to the edges of the universe in both space and time, and the boundaries of comprehension
• The very early universe lacked stars, galaxies, and even atoms
• The earliest data about the universe come from the Cosmic Microwave Background (CMB)
• Cosmic Microwave Background (CMB)


  Low-energy radiation left over from when the first atoms formed
• The CMB serves as key evidence for the Big Bang model
• The CMB offers an image of the universe about 380,000 years after its beginning
• To understand events before the CMB, physicists use particle physics and the Theory of General Relativity
• Observations of the CMB and the subsequent universe are interpreted using these theories
• Particle physics experiments, like those at the Large Hadron Collider (LHC), recreate early universe conditions
• The discovery of the Higgs boson at CERN is an example of such experimental evidence
• These experiments provide evidence for events prior to the release of energy that created the CMB
• The first 10^−43 seconds (Planck era)

  1. Physics cannot explain this period due to extreme conditions

  2. Universe was extremely small, dense, and hot

  3. Referred to as a singularity

  4. Space and time began, gravity became distinct

  5. Temperature was 10^32 degrees Celsius, universe was 10^−35 cm across
• 10^−43 seconds to 10^−36 seconds (Grand unified era)

  1. Strong nuclear, weak nuclear, and electromagnetic forces were unified

  2. Matter and antimatter particles formed and annihilated each other
• 10^−36 seconds to 10^−32 seconds (Inflation era)

  1. Exponential expansion proposed to explain universe features

  2. Universe expanded by a factor of 10^26, reaching about 10 cm across

  3. Alan Guth proposed inflation in 1980 to explain the uniformity of the CMB and universe's flatness

  4. Inflation smoothed out deviations in flatness

  5. Small CMB variations detected by Planck observatory support inflation
• Electroweak era (10^−32 seconds to 10^−12 seconds)

  1. Strong nuclear force emerged

  2. Higgs boson formed, giving particles mass
• Quark era (10^−12 seconds to 10^−6 seconds)

  1. Particles like quarks, electrons, and neutrinos appeared

  2. Matter had a slight bias over antimatter, preventing total annihilation
• Hadron era (10^−6 seconds to 3 minutes)

  1. Temperature dropped, allowing quarks to form protons and neutrons (hadrons)

  2. Most hadrons annihilated with antiparticles; leptons like electrons dominated
• Nucleogenesis (3 minutes to 20 minutes)

  1. Annihilation with antimatter decreased

  2. Critical fusion phase occurred, forming most of the universe's nuclei
• Big Bang (~14 billion years ago)


  • Released an incomprehensible amount of energy
  • Universe initially composed of pure radiation, too hot for matter to exist
• Cooling and Formation of Matter

  1. Expansion led to cooling, allowing radiation to condense into matter

  2. E = mc²: Huge amounts of energy required to form small amounts of matter

  3. As matter formed, further cooling occurred, producing more matter in a feedback loop
• Inflation


  Period of rapid expansion in the early universe
• Matter


  • Electron (negative charge)
  • Same mass and behavior as positron
• Antimatter


  • Positron (positive charge)
  • Same mass and behavior as electron
• Mutual Annihilation


  1. When matter and antimatter collide, they annihilate each other

  2. Example: Electron + Positron → Gamma radiation (e− + e+ → γ)

  3. Extensive annihilation occurred in the early universe

  4. Resulted in a universe with more matter than antimatter
• First Particles


  • Fundamental particles: Leptons, Neutrons, Quarks
  • Zero mass particles: Gluons, Photons
• Formation of Hadrons


  1. As temperature falls, quarks combine to form hadrons (protons and neutrons)

  2. Initially formed as isolated particles

  3. Explains the abundance of hydrogen in the universe
• Proposal by George Gamow and Ralph Alpher


  1948
• Proposal explained the formation of over 99% of the atoms in the universe
• Protons and neutrons in the early universe

  Interacted with electrons and neutrinos, interchanging roles