Big Bangs and Dark Matter

Dr Alan BarrPhysics lecturerUniversity of Oxford

Hubble

The very BIG

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

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

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

The whole story?

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

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!

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

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

Note concerning “high energy”

Spark could jump 5000 km in air(~radius of The Earth)

Our detectors

LHCb

ATLAS

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

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

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!Need to “see” the invisible!

How to “see” the invisible?

proton proton

short-livedexotic

short-livedexotic

Invisibleexotic

Invisibleexotic

Visibleparticle

Visible particle

missing

z

x

Useful?

Future discoverie

s will l

ead to new

technologiesFuture disc

overies w

ill lead to

new

technologies

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

First subatomic particle to be isolated, in 1897

J.J.Thompson needed just over 13 V to remove electrons from atoms.