GEOL 105
Origin of the Universe
Ptolemaic
geocentric
system
From Ptolemy
(100-170 CE),
Egyptian
astronomer
Creation of Adam by Michelangelo
The Grand Canyon in Arizona took 5-6 million years to form.
Earth is 4.5 billion years old
The nighttime sky paradox and the origin of time
The notion of universe
Aristotle (384-322 BCE) acknowledged two “worlds”: Earth and
the Moon. Planets were indistinguishable from stars, except for
retrograde motion.
The word “planet” is derived from the Ancient Greek for
“wandering star”.
Nicolaus Copernicus (1473-1543) describes the solar system
as heliocentric, with the planets circling the sun rather than
Earth.
Galileo Galilei (1564-1642) used recently invented telescope to
observe the sun, moon and planets. Found the mountains and
craters of the moon and revealed the planets to be worlds in
their own right.
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Galileo de nes the Universe (from Latin universus: all in one +
versus: to turn, be changed) as a single entity where the same
physical laws apply.
Galileo’s sketch of the Moon
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Aristotle (384-322 BCE) acknowledged two “worlds”: Earth and
the Moon. Planets were indistinguishable from stars, except for
retrograde motion.
Giordano Bruno
(1548—1600)
Campo de' Fiori,
Rome, Italy
The word “planet” is derived from the Ancient Greek for
“wandering star”.
Nicolaus Copernicus (1473-1543) describes the solar system
as heliocentric, with the planets circling the sun rather than
Earth.
Galileo Galilei (1564-1642) used recently invented telescope to
observe the sun, moon and planets. Found the mountains and
craters of the moon and revealed the planets to be worlds in
their own right.
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Galileo de nes the Universe (from Latin universus: all in one +
versus: to turn, be changed) as a single entity where the same
physical laws apply.
Galileo’s sketch of the Moon
Our galaxy:
The Milky Way
Sagittarius A*
(black hole)
You are here
The Milky Way encompasses 100 to 400 billion stars
The Big Bang: The birthplace of everything
Melvin Slipher (1875-1969)
Edwin Hubble (1920)
•
•
Observations at Mt Wilson’s
laboratory corroborate Slipher’s
observation to include 39 galaxies,
•
All galaxy are moving away from
each other, the most distant at the
greatest velocity.
•
The Big Bang theory is born!
•
Discovered 12 galaxies beyond
the Milky Way (1913) in
Flagsta , Arizona at the Lowell
Observatory.
All rst showed the “red shift”,
a doppler e ect, indicating that
all galaxies are speeding away.
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Arno Penzias and Robert Wilson (1965)
•
Discovered the earth is bathed in cosmic microwave
background radiation (CMB) (the oldest
electromagnetic radiation) that comes from everywhere.
•
Con rms the Big Bang theory.
Stellar nurseries and individual stars in the Carina Nebula
revealed by the James Webb space telescope (2022)
Electromagnetic spectrum
Speed of light: c=299 792 458 m/s.
Redshift
• Just like any wave, light changes
frequency as a function of the relative
speed between the source and
receiver. You can experience this
phenomenon with sound waves as the
Doppler e ect, which distorts the
pitch of a sound if the source if coming
towards, or away from you.
• All the galaxies in the Universe show
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this e ect as a red shift in the light
spectrum, indicating that they are all
moving away from each other.
Expanding universe
• The redshift of galaxies shows that the
Universe is expanding outward.
• If we rewind the process, all the galaxies
converge to a single point, a singularity
called the Big Bang.
• The time it would take for the Universe to
expand at its current rate (the Hubble
constant) from a small volume (say, 1
meter) to its current size provides an
estimate of the age of the Universe: 13.8
billion years.
• When the Earth was born, 4.5 billion years
ago, the Universe was already 9.3 billion
years old.
The visible universe
• The theoretical limit of the visible Universe is the distance traveled at the speed of light
since the Big Bang: 13.8 billion light-years.
• The size of the universe size is unknown and it may be in nite in extent.
• The most distant objects currently visible are also the oldest. Some currently visible
objects may currently no longer exist.
Close/recent
Solar
System
Orion arm
Milky Way
Galaxy
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Earth
Far/old
Cosmic Microwave
Background radiation
Seeds of
galaxies
•
•
The liberation of light.
At this point in the expansion, the Universe is 380,000 years old.
Temperature range: ±200 microKelvin.
Formation of the Universe
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Correspondence between
mass and energy
E = m c2
•
At the end of the Dark Ages,
uctuations of density of the ambient
Hydrogen-Helium gas caused
gravitational attraction, leading to
the concentration of matter in vast
clouds.
•
Within these clouds, 300 million years
after the Big Bang, the rst stars
were born. The production of
galaxies peaked by ~1-3 billion years
after the Big Bang.
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Formation of galaxies
Stopped here
Galaxies
Galaxies are clusters of stars that randomly
orbit the center.
•
Galaxies often assume ellipse, disk, or spiral
shapes. Barred galaxies that are at and
appear to be spinning about a central mass,
like the Milky Way and Andromeda galaxies.
•
The center of galaxies gets most of the mass
and forms a supermassive black hole.
•
Only a tiny fraction of the total galactic mass is
taken up by observed stellar mass. There is an
immense amount of invisible mass within
galaxies called Dark Matter.
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Singularity
Start of
chemistry
First
minerals
The Life of Stars
• Stars di
er in color (temperature)
and luminosity (size).
• 85% of all stars, including the Sun,
fall in the main sequence of the
Hertzsprung-Russell (H-R) diagram.
• Red giants, like Betelgeuse in the
Orion constellation, are larger or
colder.
• White dwarfs are dying stars. Fuel
for fusion reactions is exhausting.
• The smaller a star, the longer it can
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live. A 1S star lives 10 billion years.
Binary star
systems
• A binary star system is two stars orbiting
around a common centre of mass.
• Many stellar systems (50-85%) are binary
or multiple-star systems.
• In some systems, stars are so close that
their surfaces are in contact with exchange
of material.
• In other systems, binary stars may be
separated by a few thousand Astronomical
Units with orbital periods of hundreds of
years.
Supernovas
• The life cycle of a massive
star (100S) ends with the
explosion of the super-dense
core: a supernova.
• Matter is scattered in the
surrounding galaxy, forming a
nebula that can accrete into a
new solar system.
• The remains of the core
collapse into a black hole so
dense that light cannot escape.
The Event Horizon Telescope’s image (2019) of the black hole at
the center of Messier 87, a large galaxy in the Virgo cluster.
Where do elements come from?
Formation of di erent types of
elements by nucleosynthesis
(process that creates new atomic
nuclei from pre-existing nucleons,
primarily protons and neutrons).
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Big Bang nucleosynthesis (about
three minutes after the big bang),
creation of hydrogen (75%), helium
(24%) and lithium (1%).
Stellar nucleosynthesis (creation
of chemical elements by nuclear
fusion reactions between atoms
within stars and novas).
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Smallest quantum
structures
Scales of matter
Visible
Universe
10-35 meter
1027 meter
Cluster of
galaxies
1024
The big bang theory combines
astronomical observations and the
standard model of all matter and
energy.
Quarks
Galaxy
1021
10-18
10
Humankind is placed at the center
of the visible Universe (tautology)
and at the center of the scales of
matter, from 10-35 m of the smallest
quantum structures to the 1027 m
of the visible Universe.
Nucleus
16
Nearest
star
10-15
1014
Solar
System
10-10
Atom
109
10-5
1 meter
Cell
107
Earth
Human
Sun