MSC Bethancourt
Lecture
What does Dark Matter
have to do with the Big Bang
Theory?
Prof. David Toback
Texas A&M University
Mitchell Institute for
Fundamental Physics and Astronomy
October 2014
David Toback,
MSC Bethancourt
October
2014 Lecture
1
Prologue
We live in a time of remarkable scientific
understanding
Scientists are arrogant/crazy enough to think
that it may be possible to solve major problems
in Astronomy, Cosmology and Particle Physics
with a single discovery that ties all three
together
Idea: Dark Matter is a particle that was created
right after the Big Bang and has had a major
impact on the evolution of the Universe and the
stuff in it
Goal of this talk: To show you how all this might
just tie together
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David Toback, MSC Bethancourt Lecture
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Overview of the Talk
Will talk about some of the most exciting
questions in all of science one-by-one:
• What IS Dark matter and what is some
of the evidence for it?
• What is the Big Bang Theory?
• What does Dark Matter have to do with
the Big Bang and the evolution of the
Universe?
• 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 two things:
– 1) The orbits of planets as they move around
the solar system and
– 2) Stars as they move around a galaxy
• Prediction: both have very massive centers so we
expect the data to look consistent with that
• Data:
– For the solar system, the data agree
perfectly
– For the stars in the outer part of galaxies,
the prediction doesn’t work at all
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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)
Lots of other evidence for dark matter like gravitational
lensing, but that’s for another day…
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Our Place in the Universe
You are here
The 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
~13.7
billion David
years
You listen
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Toback, MSC •Bethancourt
Lecture to me talk17
Artists Conception of the Big Bang
It all started with a Big Bang
Bang
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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
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Proton
Quark
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A Millionth of a Second after the Big
Bang
The quarks have combined to form
Protons and Neutrons
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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
half a billion
years, because
of gravity,
atoms combine
to form the
first stars and
galaxies
October 2014
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 (by
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David Toback, MSC Bethancourt Lecture
mass) in the
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
October 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
Low Temperature
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 2014
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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David Toback, MSC Bethancourt them
Lecture 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
October 2014
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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?
More on General Relativity, Quantum
Mechanics and Particle Physics
– Has a lab (if you want) and can be
used as a Tier 2 Science Distribution
credit
– There is an option to take is an
Honors class
http://faculty.physics.tamu.edu/toback/109/
October 2014
David Toback, MSC Bethancourt Lecture
http://people.physics.tamu.edu/toback/TalkScience
/
38
Conclusions
• It’s an incredibly exciting time to be a
scientist!
• Astronomy, Cosmology and Particle
Physics are all coming together
• Perhaps we 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!
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Abstract
Scientists have entered a golden age of discovery. We are
starting to be able to answer some of the most exciting
questions ever asked, including questions that touch on
the Big Bang, the fundamental building blocks of nature,
and the Dark Matter that fills the Universe. In this
talk I will talk about Astronomy, Cosmology, Particle
Physics and The Universe and the reasons to think that
the biggest things in the Universe (like the Universe
itself) and the smallest things (like quarks and
electrons) are inextricably linked. Indeed, many of us
believe there is a new, fundamental particle just around
the corner waiting to be discovered that could all these
things together
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Prologue
(Apologies for the simplistic definitions)
• Astronomy is the study of things we
can see through telescopes… Stuff in
Universe (space)
• Cosmology is about trying to
understand the origin and evolution
of the Universe
• Particle Physics is about trying to
understand the smallest things that
make up the stuff in the Universe
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