Dark Matter and the
Big Bang Theory
Prof. David Toback
Texas A&M University
January 2014
January 2009
David Toback, Saturday Morning Physics
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Overview
Two of the most exciting topics in all of
science are Dark Matter and the Big Bang
Start with questions:
• What IS Dark matter and what is the
evidence for it?
• What IS the Big Bang Theory?
• What does Dark Matter have to do with
the Big Bang?
• What are scientists doing today to
discover Dark Matter?
Final Thoughts
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What is Dark Matter?
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Dark Matter
What is
some of
the
evidence
for Dark
matter?
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How stars move in galaxies
• Start by considering the case that
there IS no Dark Matter in galaxies
• Can use laws of gravity to predict the
orbits of planets and stars as they
move around the solar system and
galaxy
• For the solar system, the data agree
perfectly, but for the outer part of
galaxies it should look like stars in
orbit around a massive center
• Problem: This isn’t what the data
shows
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David Toback, Saturday Morning Physics
http://people.phy
sics.tamu.edu/to
back/Talks/Video
/Lab4_SS1_video
.swf
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As the Galaxy Turns
http://faculty.physics.tamu.edu/toback
/Talks/Video/Lab4_GX1_video_slow.sw
f
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Data well explained by lots of
“Dark Matter” we can’t see
This is where it gets its name
In some sense, the name is a
statement of almost all we know
about it (it doesn’t interact
with light, and it has mass)
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Our Place in the Universe
You are here
In some ways, Dark
Matter surrounds
the galaxy like the
water in a fishbowl
surrounds a fish in
the middle of the
bowl
Not exactly the
same… denser in
the middle because
of the pull of
gravity
What is the Big Bang Theory?
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Not that Big Bang
Theory
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A Big Bang
Occurred… Then
What?
The Story of
the Universe
since the
Beginning
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Observe lots of galaxies
with the world’s best
telescope
We notice that All the far
away ones are moving away
from us VERY quickly
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So What?
All the stuff in the galaxies
appears to have come from a
singlehappened
point in space
What
in the~13.7
past?
billion
years
ago
Run the clock backward in time
Name this time The Big Bang
 A moment of Creation
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Slightly more complicated than that…
• As best as we understand the
Universe began with a Big
Bang
– A REALLY Big Bang
• Then what?
• How did we get from the bang
to the Universe we have
today?
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A Brief History of Time
• Zero
•
•
•
•
•
•
• The Big Bang 
produces lots of
particles
One millionth of one
• Quarks combine to form
second after the Bang
protons and neutrons
A few minutes
• Protons and Neutrons
combine to form the
nucleus of an atom
A few hundred
• Nuclei and electrons
thousand years
combine to form atoms
100 million to 1 billion • Atoms combine to form
years
Stars and Galaxies
9 billion years
• The Earth and our solar
system forms
David Toback, Texas A&M University
~13.7
billion
years
You listen to me talk16
March 2011
Davidson•Scholars
Artists Conception of the Big Bang
May 2009
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The very early Universe
Lots of free particles just hanging around…
Universe is so hot that quarks can’t combine
to make protons/neutrons
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Later, Quarks Combine to Form
Nucleons
qqq  Proton
Quark
Nuclear
Reaction
Quark
May 2009
Proton
Quark
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A Millionth of a Second after the Big
Bang
The quarks have combined to form
Protons and Neutrons
May 2009
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Creating Heavier Nuclei
Proton
Proton + Proton  Deuterium
Nuclear
Reaction
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Deuterium
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A couple hundred thousand years
later: Atoms
Proton
ElectroMagnetic
Reaction
Hydrogen
Atom
Electron
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Wait a Billion Years
After about a
billion years,
because of
gravity atoms
combine to
form the first
stars and
galaxies
May 2009
Our galaxy, the Milky Way
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After about
9 billion
years our
solar
system and
the Earth
form
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Recent History: Life on Earth
• Earth is about 4 or 5 billion
years old
• Evidence that microbial tracings
existed on Earth about 3.5 billion
years ago
• Humanoids, like “Lucy” existed a
mere 3 million years ago
• Homo-sapiens at around 100,000
years ago
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What does Dark Matter have to do
with the Big Bang Theory?
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The Known Particles
– No known particles have
the properties of Dark
Matter
– Other reasons to believe
there are new fundamental
particles to be discovered
– For example, we just
discovered the Higgs
Boson
– Maybe Dark Matter is a
New Particle!
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What IS the Dark Matter?
We don’t know…
Hypothesis: The Dark Matter in the
Universe is made up of LOTS of particles
that we haven’t discovered yet!
Best Guess: Huge numbers got created in
the Early Universe like everything else
and are still here today!
Today: Observe 5 times more
Dark Matter than Atoms in the
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Universe
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What are scientists doing today to
discover Dark Matter?
Just mention two of the fun
experiments being done here at Texas
A&M!
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Some Sources of Dark Matter
are Cheap
You are here
January 2014
Our Sun is
Moving
through our
Galaxy…
Lots of Dark
Matter is
hitting the
Earth every
second
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Experiment
Dark Matter
Particle
Ping
I saw it!
Eureka!
Atom in Detector
Detector
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Can we Make and Discover
Dark Matter?
• High energy collisions between
particles in the Early Universe
• Recreate the conditions like
they were RIGHT AFTER the
Big Bang
• If we can produce Dark
Matter in a collision then we
can STUDY it
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More Expensive Dark Matter?
High Energy Collisions  Dark Matter Particles
LHC  ≈1 ps after the Big Bang
Detector
Proton
October 2011
Proton
Ok… Its more complicated
than this since Dark Matter
Particles don’t easily
interact with detectors…
Nor do we usually produce
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Research Topics Seminarthem directly
Aerial View of the LHC
Lake Leman
One of the largest and
the most complex scientific
CMS
instrument ever conceived &
Geneva
Airport
Two huge
detectors
built by humankind
27 km in Circumference!
Collides high
energy protons
p
p
ATLAS
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How does it
do it?
Accelerates
protons to
REALLY
high
energies,
then bashes
them
together
http://people.physics.tamu.edu/toback/Tal
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ks/Video/particle_event_full_ns.avi
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Final Thoughts
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Interested in learning more?
• Physics department now offers a course
entitled “Big Bang & Black Holes”
(ASTR/PHYS 109)
– Covers Stephen Hawking’s “Brief
History of Time”
–
–
–
–
–
Origin and Evolution of the Universe
How do stars form?
What is Dark Matter? Dark Energy?
What are Black Holes?
General Relativity & Quantum
Mechanics
– Particle Physics
– High School Students:
• Get your school to get involved with
the Talk Science Program
http://faculty.physics.tamu.edu/toback/109/
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David Toback, Saturday Morning Physics
http://people.physics.tamu.edu/toback/TalkScience
/
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Conclusions
• It’s an incredibly exciting time to be a
scientist!
• Astronomy, Cosmology and Particle
Physics are all coming together!
• Starting to understand the role of
Dark Matter in the Universe since the
Big Bang!
• If our understanding is correct, a
major discovery may be just around
the corner!
Wanna join us?
We need your help!
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January 2009
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