Big Bang
…..was actually very small and quiet
Atoms are mostly empty space
Early Universe: a strange place
• Photons are particles of light that behave
like waves
• Early universe was so HOT that when 2
photons collided, they made matter
• E = mc2
• 2 photons make an electron-antielectron
pair (antielectron = positron)
• Matter and antimatter
Early Universe
• In reverse, the 2 particles annihilate each
other and create photon energy
• There are also proton and antiprotons
• Neutrons and antineutrons
Quantum Mechanics
• The theory of the very small
• Subatomic particles
General relativity
• Einstein
• Theory of the very big
• Gravitational fields warp space and time
The Theory of Everything
• Someday scientists may be able to merge
Quantum Mechanics with General
Relativity
• Until then, science can not describe the
very very early Universe
The 4 Forces Today
• Gravity is the dominant force on large
scales
• Electromagnetic force dominates
biological and chemical reactions
• Strong and Weak forces determine what
happens in the atomic nucleus, important
in fission and fusion
GUT Force:
• GUT force = all the forces in the early
universe merged together : a Superforce
• Gravity
• Electromagnetism
• Strong force
• Weak force
The First Instant: Planck Time
• Named after Max Planck, one of the
fathers of Quantum Mechanics
• Universe is 10-43 second old
• “Creation” of the Universe
• During the Planck era (up to 10-43
seconds) gravity force “freezes out” as a
separate force
GUT era: 10-43 -10-35 seconds
• 2 forces exist: Gravity and GUT
• Lasts until universe cools to 1027 K
• At 10-35 seconds, strong force “freezes
out”
• 3 forces now exist: gravity, strong and
electroweak
• Freezing out of strong forces releases a
huge amount of energy, causing rapid
expansion of universe
Inflation
• Universe expands suddenly and
dramatically
• In 10-33 second, a piece of the universe the
size of an atomic nucleus would have
expanded to the size of our solar system
The Electroweak era
• Electromagnetic and weak forces are still
merged
• Gravity and strong force are separate
• Intense radiation fills space
• Matter and antimatter particles are created
and immediately destroyed
• Universe expands and cools to 1015 K,
which is 100 million times hotter than sun
Particle Era: 10-10 seconds
• The end of the electroweak era and
beginning of particle era have been
confirmed in experiments at CERN particle
accelerator
• At this temperature, the electromagnetic
force freezes out, and now the 4 forces
are all present as separate forces
Particle Era: 10-10 seconds
• Tiny particles are now abundant:
electrons, neutrinos, quarks, antimatter,
and other building blocks of protons and
neutrons.
• At .0001 seconds, temperature has cooled
so that quarks can no longer exist on their
own, and combine to form protons and
neutrons
Particle Era: ends at .001 seconds
• Temperature = 1012 K
• No longer hot enough to spontaneously
produce matter from energy
• Matter annihilates antimatter, making
photons
• There are more protons than antiprotons
• Leftover matter makes up all the matter in
the Universe, including us!
Era of Nucleosynthesis
• Protons and Neutrons left over try to fuse
together to make heavier particles, but it is
still too hot, and they break up
• Density in expanding universe has
dropped so much that fusion stops despite
temperature of 109 K (hotter than sun)
Era of Nucleosynthesis
•
•
•
•
75 % are Hydrogen nuclei
25% Helium nuclei
Some Lithium
This composition of the universe is
essentially the same today, except for the
small amount of heavier elements made
by stars
• Era ends at 3 minutes
Era of Nuclei
• Universe is now a hot plasma of Hydrogen
and Helium nuclei
• Electrons roam free from neutrons
• If a nucleus captures an electron to make
an atom, a photon quickly ionizes it
• Era lasts 300,000 years as universe
expands and cools to 3000 K (half the
temperature at the sun’s surface)
Era of Atoms
• Universe is now cool enough that the
Hydrogen and Helium nuclei capture
electrons for good, making the first stable
atoms
• Photons stream freely across the universe
(Cosmic Background Radiation)
Era of Atoms
• Universe is a mix of neutral atoms and
plasma
• Gases assemble to make protogalactic
clouds
• Stars begin to form in these clouds
• Era ends at about 1 billion years old
Era of Galaxies
• Lasts from 1 billion years old till today
(about 15 billion years old)
• Stars make heavier elements
• Planets form from these around stars
• Life forms on planet(s)
• Here we are!
Carl Sagan:
“ These are the things that Hydrogen atoms
do, given 15 billion years of cosmic
evolution”
Evidence for Big Bang
• 1965 Bell Labs, New Jersey
• Penzias and Wilson working on satellite
antennas detect “noise” in all directions
• Meet Princeton team on airline flight working on
theoretical calculations that show there should
be leftover radiation from Big Bang
• Win Nobel Prize in Physics 1978 for discovery of
Cosmic Background Radiation
Evidence for Big Bang
• 1990’s COBE Cosmic Background
Explorer
• Maps temperature of sky 2.75 K
• Shows variations in density of universe
Questions
• Why matter and not antimatter?
Particle accelerators create equal amounts
of both
Questions
• Will the Universe expand forever “Open
Universe” or reverse itself?
Possible end…..
1.
2.
3.
4.
Stars will die, distances increase
All that is left is massive black holes
Most protons will fall apart by 1040 years
Black Holes will evaporate (Hawking
Radiation) by 10100 years
5. All that will be left: photons and
subatomic particles separated by
enormous distances
6. Nothing more will change = end of time?
7. or will there be a rebirth of the Universe?