The Birth of the Universe
What were conditions like in the early universe?
● The universe is expanding.
● The early universe must have been extremely hot and dense.
How were particles created?
● Photons converted into particle-antiparticle pairs and vice versa.
● E = mc^2
● The early universe was full of particles and radiation because of its high temperature.
Four Known Forces in the Universe:
● Strong force - holds nuclei together.
● Electromagnetism - holds atoms and molecules together.
● Weak force - important for fusion/fission, affects neutrinos.
* Forces begin to unify at high temperatures.
How did the early universe change with time?
● First era after the Big Bang
● Before Planck time (~10^-43 second)
● No theory to explain the Universe during this time.
● GUT: Grand Unified Theory
● Strong, Weak, and EM operated as a single force.
● Lasts from Planck time (~10^-43 sec) to end of GUT force (~10^-38 sec).
● Strong force separates: 3 forces
● Lasts from end of GUT force (~10^-38) to end of electroweak force ()
● 4 distinct forces
● Number of particles ~ number of photons
● Amounts of matter and antimatter nearly equal (roughly 1 extra proton for every 10^9
proton - antiproton pairs)
Era of Nucleosynthesis
● Begins when matter annihilates remaining antimatter at ~0.001 second.
● Nuclei begin to fuse.
Era of Nuclei
● Helium nuclei form at age ~ 5 minutes.
● Universe became too cool to blast helium apart.
● Sets the amount of Helium we see today - 25% helium.
Era of Atoms
● Atoms form at age ~ 380,000 years
● Temperature of Universe ~ 3,000 K
● Cosmic microwave Background (CMB) radiation released.
Era of Galaxies ● Galaxies form at age ~ 1 billion years
Primary Evidence for the Big Bang Theory
● We have detected the leftover radiation from the Big Bang (specifically CMB radiation).
● The Big Band theory correctly predicts the abundance of helium and other light elements.
1. How do these observations of CMB support the Big Bang theory?
● The cosmic microwave background - the radiation left over from the Big Bang -
was detected by Penzias and Wilso