Big Bangs and
Dark Matter
Dr Alan Barr
Physics lecturer
University of Oxford
The very BIG
Hubble
Spectra and redshifts
Mega parsec = 3.26 million light-years = 3.1 x 1016 m
Echos of something big
WMAP satellite
What was formed: matter
Only three elements are
formed in the Big Bang
All other elements are
formed in stars
Differences between materials are due simply to the number of protons
and electrons in their atoms.
The very SMALL (what we see)
x5
cells: 50 μm
x 20
x 10000
cell nucleus: 10 μm
x 50000
atom: 100 pm
dna: 2 nm
x 5->
atom nucleus: 2 fm
proton
A hundred billion atomic nuclei lined up in a row would be the width of a human hair
The whole story?
The bit we understand…
Matter & Forces
Commonplace particles
Matter Particles
Electron, e
Quarks
u quark
Photon, γ
d quark
Gluon, g
Not to scale!
 Components
Leptons
u
c
t
e
d
s
b
νe νμ
Force carriers
g
W
Z
γ
μ
τ
ντ
Out there?
h
G
and theory largely understood (maths)
 Underlie all of physics, astronomy, chemistry, life!
Big
questions
What is dark matter made of?
Where has all the anti-matter gone?
Where do the particles get their mass from?
What else is out there?
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!
http://www.youtube.com/theATLASExperiment#p/u/0/NhXMXiXOWAA
Our accelerator
The Large Hadron Collider, CERN
Geneva (Swiss-French boarder)
Electric waves speed particles up
1232 magnets each 8-Tesla
bend protons in a circle
Large Hadron Collider
Note concerning “high energy”
Spark could jump 5000 km in air
(~radius of The Earth)
Our detectors
ATLAS
LHCb
Big
questions
What is dark matter made of?
Where has all the anti-matter gone?
Where do the particles get their mass from?
What else is out there?
Mass and the “Higgs Boson”
The Higgs Field
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
In this analogy the Higgs Boson
is a treacle-ball – something which
allows us to see the treacle itself
High energy collisions ought to make Higgs Bosons
The “tentative” evidence
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!
How to “see” the invisible?
Invisible
exotic
missing
Visible
particle
short-lived
exotic
proton
proton
short-lived
exotic
x
z
Visible particle
Invisible
exotic
Useful?
Uses of the electron
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
Discovery of the electron
J.J.Thompson
needed just over 13 V
to remove electrons
from atoms.
First subatomic
particle to be isolated,
in 1897