The Big Bang

oooo
oooo
oooo

oooo

BSL Version
o

• The Big Bang is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now and it is still stretching.
  o
  o
  o

oooo

oooo
oooo
oooo

• One ten million trillion trillion trillionth of a second
  In order to explain what happened scientists use measurements of time that are very small.
  o

• At first…
  The Universe was unspeakably small and hot – getting larger and cooler ever since.
  o
  o

Four fundamental forces

oooo

• Four fundamental forces govern interactions between all objects in the universe.
  o
• This illustration shows above the four fundamental forces of the universe (clockwise from top left):
  o
  – gravity
  – electromagnetism
  – weak forces
  – strong forces
  o

oooo

oooo
oooo
oooo

• About one-billionth of one second after the Big Bang.
  o
• The Universe lay in a dense sea of quarks, where the first particles (neutrons and protons) were beginning to form.
  o
  o

Dense sea of quarks

• A quark is a tiny particle which makes up protons (postive +) and neutrons (negative -).
  o
  o

oooo
oooo
oooo

• About three minutes after the Big Bang there was a brief period of nucleosynthesis when quarks joined together to form protons (+), and neutrons (-).
  o
• First nuclei – Hydrogen and helium formed.
  o
  o

• The early Universe after the Bang Big completely opaque (like a thick fog ~ no light to pass through during the dark ages).
  o
• Because the super-hot plasma where the light (photons) constantly scattered off free electrons and protons, preventing it from travelling far.
  o
• During this period, the temperature was so high that electrons and protons could not combine to form neutral atoms. 
  o
• This “cosmic fog” cleared as the universe expanded and cooled enough for electrons and protons to form neutral atoms (recombination), allowing light to travel freely.
  o

After 380,000 years…

oooo

• The Universe cooled enough for electrons and nuclei to combine, forming neutral atoms (mostly hydrogen and helium), making the universe transparent and releasing the Cosmic Microwave Background (CMB) radiation.
  o
• Then it become cool enough for protons (+) and neutrons (-) to capture electrons.
  o
• The first atoms form.
  o
  o

• After recombination, the universe was filled with neutral gas (mostly hydrogen and helium), but no stars or galaxies yet existed, so it was dark.
  o
• Gravity pulled gas and dark matter together, forming dense clouds that ignited into the first massive stars (Population III stars) and the first small galaxies, ending the Dark Ages.
  o
• The Universe remained completely opaque.
  o
• Then it become cool enough for protons (+) and neutrons (-) to capture electrons and form atoms.
  oooo
  oooo

• The first stars began to shine.
  oooo
  oooo

• Dark matter forms a scaffolding or filamentary strands across the universe, and galaxies appear along these strands.
  o
• Gas falls into the halo ~ ordinary matter (hydrogen, helium) is pulled into these halos as it cools and condenses, it forms: stars, star clusters and full galaxies.
  o
  o

• Galaxies and Dark Matter ~ galaxies form in dark matter cradles on cosmic structure.
  o
• Dark matter collapes first ~ after the Big Bang, dark matter began clumping under gravity. Because it doesn’t interact with light or radiation, it could collapse earlier.
  o
• Without dark matter’s stabilising gravitational pull, galaxies would not have formed or held together in the shapes.
  o
• These clumps become “halos” ~ each halo is a gravitational bubble (a region where dark matter density is high.)
  o

• Today Universe is epanding faster than ever ~ driven by dark energy.
  o
• Cooling slowly, now around -274°C.
  o
• Growing more structured, with galaxies clustering into filaments and voids.
  o
• There is still much to be discovered about the Universe and the Big Bang.