Early Universe and Star Formation

• Universe began as "sleepy baby" - warm, dark, filled with hot hydrogen and helium clouds
• First generation stars: massive, violent lives, forged new elements, exploded
• Countless stars born, refined available gas, cycled matter through generations
• Not all gas returned - each generation creates more red dwarfs
  • Red dwarfs burn slowly, live trillions of years
  • When they die, become white dwarfs (don't return gas to universe)
  • Gas also locked in neutron stars and black holes
• Over 90% of stars that will ever be born have already been born

Current and Near-Future Universe

• Today: universe great home for billions more years
• Most gas already used up or trapped
• Next few hundred billion years: fun time for galactic exploration
• Large stars and sun-like stars will die out
• Eventually almost all stars will be red dwarfs slowly dying

Distant Future: White Dwarf Era

• Few trillion years: cosmic gas finally runs out
• Galaxy composition: 88% white dwarfs, 2% neutron stars/black holes, 10% gas giants/brown dwarfs
• White dwarfs characteristics:
  • Corpses of old stars, Earth-sized but half sun's mass (some much more)
  • Third densest objects after neutron stars/black holes
  • Million times denser than sun
  • Surface temperatures up to 150,000°C
  • Dim, hot, dense spheres doing nothing

White Dwarf Death and Black Dwarf Formation

• White dwarfs slowly lose heat over 10+ trillion years (700x current universe age)
• Cool down to become black dwarfs - spheres cold as space itself
• Over trillions of years: all objects either ejected into void or fall into central black holes
• Quintillion years: all galaxies evaporated, every object isolated

Black Hole Era

• Black holes die via Hawking radiation
• Takes googol years (10^100) for last supermassive black hole to die
• Final flash of light when they evaporate

Black Dwarf Physics

• Black dwarfs: Earth-sized, star-massive, near absolute zero
• Internal structure:
  • Matter squeezed to millions of times Earth density
  • Electrons can't combine with nuclei to form atoms
  • Nuclei compressed into rigid lattice
  • Electrons form plasma, hold star together via degeneracy pressure
• Analogy: electrons like subway passengers forced into crowded train
• Quantum tunneling occurs even at near absolute zero (extremely slowly)

The Last Event: Black Dwarf Fusion and Supernova

• Fusion timeline:
  • Trillion years of nothing
  • Single fusion: two carbon nuclei → magnesium via quantum tunneling
  • 100 trillion years later: happens again
  • Oxygen nuclei → silicon over eons
  • Silicon nuclei → nickel-56 (radioactive)
• Nickel-56 decay process:
  • Decays to iron, emits two positrons (antimatter electrons)
  • Positrons annihilate with electrons
  • Fewer electrons = less pressure to support star
  • Gravity squeezes harder
• Final collapse after 10^1000 years:
  • Black dwarf loses too many electrons
  • Uncontrolled collapse → supernova
  • Implodes then explodes bright as galaxy
  • Fills empty universe with light briefly
  • Then darkness and emptiness forever

Conclusion

• This represents truly dead universe
• Timeline so vast "forever" hardly describes it
• Today's universe still best place for us
• Last interesting event unimaginably far in future