big bangs and dark matter dr alan barr physics lecturer university of oxford
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Big Bangs and Dark Matter
Dr Alan BarrPhysics lecturerUniversity of Oxford
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Hubble
The very BIG
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Spectra and redshifts
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Mega parsec = 3.26 million light-years = 3.1 x 1016 m
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Echos of something big
WMAP satellite
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What was formed: matter
Differences between materials are due simply to the number of protons and electrons in their atoms.
Only three elements are formed in the Big Bang
All other elements are formed in stars
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cell nucleus: 10 μm
The very SMALL (what we see)
cells: 50 μm dna: 2 nm
atom nucleus: 2 fm
x 5
x 20
atom: 100 pm
x 50000
proton
x 10000
x 5->
A hundred billion atomic nuclei lined up in a row would be the width of a human hair
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The whole story?
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The bit we understand… Matter & Forces
Electron, e
d quark
Photon, γ
Gluon, gNot to scale!
Commonplace particles
u quark
Matter Particles
u
Quarks
d
c
s
t
b
Leptons
νe νμ ντ
e μ τ
Force carriers
W Z γg
Components and theory largely understood (maths)
Underlie all of physics, astronomy, chemistry, life!
Out there?
h G
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Where do the particles get their mass from?
Where has all the anti-matter gone?
What is dark matter made of?
What else is out there?
Big questions
NEED HIG
H ENERGY
COLLISIO
NS!
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Blue Peter guide
Take some protons Lots of these in nature!
Make them move (very fast)
Bang them together It’s good to stand back at this point
Photograph the debris Your camera-phone may not be fast enough!
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http://www.youtube.com/theATLASExperiment#p/u/0/NhXMXiXOWAA
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Our accelerator
1232 magnets each 8-Teslabend protons in a circle
Electric waves speed particles up
The Large Hadron Collider, CERNGeneva (Swiss-French boarder)
Large Hadron Collider
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Note concerning “high energy”
Spark could jump 5000 km in air(~radius of The Earth)
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Our detectors
LHCb
ATLAS
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Where do the particles get their mass from?
Where has all the anti-matter gone?
What is dark matter made of?
What else is out there?
Big questions
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Mass and the “Higgs Boson”
In this analogy the Higgs Bosonis a treacle-ball – something which allows us to see the treacle itself
Endows space with a kind of all-pervasive sticky-treacle
Interactions with this treacle gives mass to particles
They then travel slower than the speed of light
The Higgs Field
High energy collisions ought to make Higgs Bosons
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The “tentative” evidence
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What is Dark Matter?
Normal: Made from atoms Includes stars, planets, people…
Dark matter: Unknown substance (not atoms) May be a “fat cousin” of normal light We hope to make &
study it at CERN
Dark energy: Even weirder!
Need to “see” the invisible!Need to “see” the invisible!
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How to “see” the invisible?
proton proton
short-livedexotic
short-livedexotic
Invisibleexotic
Invisibleexotic
Visibleparticle
Visible particle
missing
z
x
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Useful?
Future discoverie
s will l
ead to new
technologiesFuture disc
overies w
ill lead to
new
technologies
Uses of the electron
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Big Bangs and Dark Matter
• Astronomy very large (See what’s out there)• Particle physics very small (Do it “at home”)• Both explore the structure, building blocks and evolution of the universe
• Complementary information• New discoveries lead to new technologies
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Discovery of the electron
First subatomic particle to be isolated, in 1897
J.J.Thompson needed just over 13 V to remove electrons from atoms.