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The Big Bang

The Big Bang. Necessary? Expansion of the Universe Origin of CMBR 400 photons/cc Black body temperature profile Helium content Universal nucleosynthesis (like a star) Basics Universe was hotter, denser in the past. A few assumptions Universe is a closed system Physically

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The Big Bang

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  1. The Big Bang Necessary? • Expansion of the Universe • Origin of CMBR • 400 photons/cc • Black body temperature profile • Helium content • Universal nucleosynthesis (like a star) Basics • Universe was hotter, denser in the past

  2. A few assumptions • Universe is a closed system • Physically • Heating/cooling – adiabatic • Treat like an adiabatic fluid (easy!) Energy of the Universe E=kT Second law of Thermodynamics DE=p DV Change in energy depends on change in volume Pressure defined p = 1/3 e e=energy density – all radiation early on

  3. Energy of light ef=hf So energy density = ef/volume So the energy of the Universe goes down as the size goes up Since E=kT, the temperature goes down as it expands Energy = all energy Photons, mass (via E=mc2), velocity, gravity, etc…

  4. Zero-th Step Time <0 Anything before the BB? How could we tell? Where could we look?

  5. Time=0 What’s it like? Don’t know… Gravity + QED = Quantum Gravity = ? Haven’t figured it out yet

  6. Time=10-43 sec Time=Planck time Based on quantum physics principles Temperature = 1032 K Density = 1093 gm/cc Scale = very small Interactions between energy/matter Quantum physics (QED), gravity – separate Can use them to describe characteristics of the Universe How?

  7. Some boring math… Planck lengths, time, masses… Okay what does that mean? Have to define some more stuff….

  8. Compton time – time for a mass to violate conservation of energy law This activity is known as “quantum fluctuations” Formation of particles (matter/anti-matter) out of energy, quick destruction Happens over a quantum length (Compton length)

  9. Schwarzschild Radius – “size” of a black hole Schwarzschild Time – time for a photon to travel across a black hole This defines the realm of “gravity”

  10. 2 types of ways to describe the Universe • Planck length, time = QED • Compton length, time = QED • Schwarzschild length, time = gravity The way these are related defines who is in charge – gravity or QED Funny feature: a Planck mass into the formula for Compton, Schwarzschild lengths = Planck length Also, all times are equal. Meaning? Planck mass = black hole that exists for Planck time!

  11. If mass>Planck mass Enter the realm of gravity (relativity), QED not important If mass<Planck mass QED important, gravity loses. This time, this mass, this realm is when there are two separate forces – gravity, GUT GUT = grand unified theory (QED laws)

  12. So what is REALLY happening? Mini-black holes can come into/out of existence Gravity brings them into being Hawking radiation destroys them Particles (non-black holes) come into/out of existence (Compton stuff) Have energy, some particles, strange things going on – still not easy to define (or understand).

  13. Time=10-35 sec During GUT – quarks, leptons identical Now the GUT breaks down into Strong nuclear force (quarks force) Electoweak force (lepton/photon force) Breaks “symmetry” of the Universe “Freezing out” of forces – loss of freedom Release of energy (vacuum energy) Inflation starts Quarks form (along with anti-quarks)

  14. Time=10-32 sec End of Inflation After inflation, size of Universe increased by factor of 1050 Really? Expains uniformity of Universe Flatness of Universe

  15. Time=10-12 sec Another symmetry breaking Electroweak force breaks down into electromagnetic force weak nuclear force Leptons/anti-leptons form Universe full of energy (photons), quarks, leptons

  16. Time=10-10 sec Quarks win over anti-quarks Another symmetry breaking! Protons/neutrons can form Interactions between all sorts of things Not what happens today Neutrinos forced into interactions

  17. Time=10-5 sec End of neutrino interactions Universe too cool (10 billion K) Neutrinos still out there! Where are they?

  18. Time=1-3 Minutes Nucleosynthesis Universe Temperature = Stellar interior Protons, Neutrons combine to make • H2, H3 (Deuterium, Tritium) • He3, He4 • Li6, Li7, Be7 End composition: 75% p+ (H), 25% He4 (~0.01% - the rest) Gravity starts to become noticeable

  19. Time = 1 year Energy and Matter starting to diverge Cooling down at their own rates Energy (photons) – cooled by the expansion Matter – temperature determined by photons, fewer interactions

  20. Time=380,000 years Era of Decoupling Energy + Matter intertwined before now After this, they go their separate ways Energy of photons too low to interact effectively Universe becomes “transparent” to radiation Matter (gravity) controls Universe

  21. Time <1 billion years Galaxy Formation/Cluster formation? Proto-galaxy formation? Something is starting to happen…. This would be the epoch of the largest observable redshifts Might have missed a previous step (or two)

  22. Time = Now You’re looking at this. End of story (for now)

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