The Evolution of the Universe: From Big Bang to Nuclear Fusion

1. The Formation of Matter as we know it

2. In the Beginning (as science thinks) • All matter existed in a very small space • Very dense • Temperatures were over 1032 Kelvin • Atoms, protons, neutrons, and electrons didn’t exist due to the high temperature and density • The universe was a “soup” of matter and energy • radiation

3. First Second after the Big Bang • Temperatures had fallen • 100 Billion Kelvin (179,999,999,540.6 ºF) • Neutrons, protons, and electrons began to form • Too much energy at this time to form atoms • When they ran into each other they would bounce off each other • Neutrons • Were being created and destroyed as a result of interactions between protons and electrons • Due to the amount of energy lighter electrons and protons collide to form neutrons. • Some did decay back into a positive proton and a negative electron

4. Universe continues to expand • Temperature keep falling • Protons and electrons no longer had enough energy to collide to form neutrons • Number of neutrons and electrons stabilized • 7:1, with protons outnumbering electrons

5. 100 seconds after the big bang • One billion Kelvin • 1,799,999,540.6 ºF • Neutrons and protons collide and stick together • Deuterium • First atomic nuclei • Neutron-proton pairs • Type of hydrogen with an extra neutron • Sometimes deuterium would collide to form helium nucleus • Rare occasion there would be enough collision between deuterium to form lithium

6. Universe – a few minutes old • 95% Hydrogen • 5% Helium • Trace amounts of lithium

7. 10s of thousand of years old • Matter dominated over radiation • Temp. 10s of thousands of Kelvins

8. Next few 100 thousand years • Universe expanding (factor of 10) • Temp. few 1,000 kelvin • Electrons and nuclei combined to form neutral atoms • Epoch of decoupling • At temp. of 3000 K • Atoms, photons, and dark matter

9. The proton-proton chain • All atomic nuclei are positively charged • repel one another • closer they get the stronger the repulsion • Takes a lot of energy to get them to stick together • Speeds of few 100 km/s • Creates temp. of 10 million kelvin

10. The proton-proton chain Cont. • Proton + Proton Deuterium + Energy • Deuteron is the nuclei of a deuterium • Energy is released in the form of two new particles • Positron • Positively charged antiparticle of an electron • Same properties as an negatively charged electron • Neutrino • Charge less and virtually massless particle • Move close to the speed of light (possibly faster) • Don’t really interact with anything • Penetrate several light-years of lead without stopping • Particles and antiparticles meet they annihilate each other and produce pure energy in the form of gamma ray-photons • Diagram on board

11. 200 million years after the big bang • Stars began to shine and the creation of new elements began.

12. Nuclear Fusion • Combining of light nuclei into heavier ones • Produces a lot of energy • Total mass decreases • E = mc2 • Energy = mass X speed of light • Law of conservation of mass and energy • Sum of mass and energy must always be constant • Hydrogen/helium diagram