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Is a public understanding of abstract physics concepts feasible?. Johannes P. Wessels Institut für Kernphysik Westfälische Wilhelms-Universität Münster and CERN, Geneva. Aspects of the nature of matter investigated at the Large Hadron Collider What is the nature of matter?

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is a public understanding of abstract physics concepts feasible
Is a public understanding of abstract physics concepts feasible?

Johannes P. Wessels InstitutfürKernphysikWestfälischeWilhelms-UniversitätMünster

and CERN, Geneva

  • Aspects of the nature of matter investigated at the Large Hadron Collider
  • What is the nature of matter?
  • How do we study it?
  • What are our (physicists’) physics concepts?
  • If they appear to be abstract, how do we try to motivate, communicatethese concepts?Analogies – do you find them useful?
how abstract is abstract opinions
How abstract is abstract? Opinions

Quantum Mechanics cannot be understood.Richard P. Feynman

The most incomprehensible about nature isthat she is so comprehensible.

Albert Einstein

physics is looking for guiding principles of nature

size of the universe 3 10 25 m
Size of the Universe 3*1025m

each of the 9325 dots represents an entire galaxy

at 10 21 m
…at 1021m…

…our galaxy with its roughly 1011 “Suns”

at 10 14 m
…at 1014m…

…finally our solar system

at 10 11 m
…at 1011m…

…roughly six weeks of the earth’s path

at 10 9 m
…at 109m…

…the moon’s orbit

at 10 7 m
…at 107m…

…not so unfamiliar

at 10 6 m
…at 106m…

…a 1000 km of cultural heritage

(and vacation)

at 10 5 m
…at 105m…

…space shuttle calling Geneva…

at 10 4 m
…at 104m…

…approaching GVA…

at 10 3 m
…at 103m…

…CERN just before landing

at 10 2 m
…at 102m…

…part of where CERN’s 10000 people work

at 10 0 m
…at 100m…

…in a beautiful setting

at 10 1 m
…at 10-1m…

…which gets more

and more interesting

at 10 2 m1
…at 10-2m…

…the closer…

at 10 3 m1
…at 10-3m…

…you look…

jpw - Single Cell 2008 - 24.11.2008

at 10 5 m1
…at 10-5m…

… ever more interesting …

at 10 7 m1
…at 10-7m…

…till you see things that can’t be seen with ‘normal’ light…

at 10 8 m
…at 10-8m…

…special light sources can even illuminate single molecules…

how abstract / real is this?

at 10 10 m
…at 10-10m…

…reaching atoms, that are essentially “empty” …

how familiar / correct is this?

at 10 14 m1
…at 10-14m…

…almost the entire mass of the atom is concentrated in the nucleus, which consists of neutrons and protons…

How useful is it to know that, if the earth were of that density it would fit into a cube of 300x300x300 m3?

at 10 15 m
…at 10-15m…

…neutrons and protons in turn consist of quarks and gluons.These quarks may well be point-like particles. They can NEVER be seen in solitude.

THE matter investigatedat the LHC.

physics in search for similarities
Physics - in Search for Similarities

The Complex

Synapses

The Biggest

The Smallest

Meters

Stars

K.H. Meier

composition of the universe
Composition of the Universe

Dynamics of the evolution governed by interations

-> forces

23%

72%

concept of interaction force
Concept of Interaction - Force

Newton: actio = reactioforce fields work at a distance - potential

standard model: forces are mediated by the exchange of particles

Interaction entailsscattering

Time

Feynman-Graph

Position

4 fundamental interactions
4 Fundamental Interactions

falling apples,planetary orbits

strength: 10-39

range: infinite

mediator: graviton?

television, magnets,chemical binding

strength: 1/137

range: infinite

mediator: photon

nuclear stability,

quark confinement

strength: 1

range: 10-15 m

mediator: gluon

-decay, neutron stability, neutrinos

strength: 10-5

range: 10-18 m

mediator: W,Z-Boson

4 fundamental interactions1
4 Fundamental Interactions

falling apples,planetary orbits

strength: 10-39

range: infinite

mediator: graviton?

television, magnets,chemical binding

strength: 1/137

range: infinite

mediator: photon

nuclear stability,

quark confinement

strength: 1

range: 10-15 m

mediator: gluon

-decay, neutron stability, neutrinos

strength: 10-5

range: 10-18 m

mediator: W,Z-Boson

4 fundamental interactions2
4 Fundamental Interactions

falling apples,planetary orbits

strength: 10-39

range: infinite

mediator: graviton?

television, magnets,chemical binding

strength: 1/137

range: infinite

mediator: photon

nuclear stability,

quark confinement

strength: 1

range: 10-15 m

mediator: gluon

-decay, neutron stability, neutrinos

strength: 10-5

range: 10-18 m

mediator: W,Z-Boson

4 fundamental interactions3
4 Fundamental Interactions

falling apples,planetary orbits

strength: 10-39

range: infinite

mediator: graviton?

television, magnets,chemical binding

strength: 1/137

range: infinite

mediator: photon

nuclear stability,

quark confinement

strength: 1

range: 10-15 m

mediator: gluons

-decay, neutron stability, neutrinos

strength: 10-5

range: 10-18 m

mediator: W,Z-Boson

4 fundamental interactions4
4 Fundamental Interactions

falling apples,planetary orbits

strength: 10-39

range: infinite

mediator: graviton?

things we can relate to

television, magnets,chemical binding

strength: 1/137

range: infinite

mediator: photon

nuclear stability,

quark confinement

strength: 1

range: 10-15 m

mediator: gluons

-decay, neutron stability, neutrinos

strength: 10-5

range: 10-18 m

mediator: W,Z-Bosons

things we cannot relate to

all partilces of the standard model
All Partilces of the Standard Model

really all of them?

important symmetry:

each particles has a

corresponding

anti-particle.

creation always in pairs

example the electron
Example: The Electron

Time

Position

which interaction a particle is subject todepends on its charge (charges)

In case of the electron: participates in electromagnetic, weakand gravitational interaction

electrical charge couples to the poton

strength depends on the coupling constant a

In case of the weakinteraction charge -> weak charge and

weak coupling constant

In case of the gravitational interaction charge -> mass and

gravitational coupling constant

example strong interaction
Example: Strong Interaction

Quarks are subject to the strong interaction.

The corresponding ‘charge’ is the color charge(r,g,b).

The mediators (exchange particles) are the gluons.

Position

Time

Gluons carry color charge, therefore, they interact amongst themselves strongly.

confinement
Confinement

d

all strongly bound objects are color neutral.

they are either baryons

consisting of 3 quarks

or

mesons consisting of a quark and an anti-quark.

d

u

u

Proton

u

Confinement:There are no free quarks in nature.

How do we know about them and their properties?

Pion +

the right light to look inside of things
The “Right” Light to Look Inside of Things

Vision works byscattering of‘visible’ light

“Vision” of even smaller structures viascattering of particles

 = 400-700 nm

 = h/p

the right light to look inside of things1
The “Right” Light to Look Inside of Things

Vision works byscattering of‘visible’ light

“Vision” of even smaller structures viascattering of particles

 = 400-700 nm

 = h/p

accelerators
Accelerators

Acceleration of a charge in an electric field: E = q•U

For the LHC you would need 2 times 7000 trillion batteries

slide41

…the “Light” from Large Accelerators

LHC

ALICE

SPS

jpw - Single Cell 2008 - 24.11.2008

either shoot on stationary target or collide beams
Either shoot on stationary target or collide beams

Recall Einstein’s famous equation E=mc2 for particle production

bubble chambers one of the first detectors to view complex particle production events
Bubble ChambersOne of the first detectors to ‘view’ complex particle production events.

jpw - Single Cell 2008 - 24.11.2008

slide46

LEP

SPS

L3

fully electronic “eyes” - here L3

jpw - Single Cell 2008 - 24.11.2008

slide47

…so we can “see”!

what constitutes seeing or evidence?

all particles of the standard model
All Particles of the Standard Model

have been ‘seen’that way.

only the lightest

are stable!

their masses

differ hugely

mass a puzzle
Mass – a Puzzle

mass of the proton is 938 [units of mass]

it consists of 2 up- and 1 down-quark

mass(up) = 1.5 – 3.3 [units of mass]

mass(down) = 3.5 – 6.0 [units of mass]

mass(proton) = 2 x mass(up) + 1 x mass(down)

= 9.5 – 12.3 [units of mass]

Proton

?

strong binding force leads to the mass of the proton

again - E=mc2

how do elementary particles acquire mass higgs 1
How do Elementary Particles Acquire Mass? - Higgs (1)

in strict analogy to a cocktail party

The room is filled with physicists, entertaining lively discussions aka as small talk. They constitute the Higgs-field (which is everywhere not just in this room!).

how do elementary particles acquire mass higgs 2
How do Elementary Particles Acquire Mass? - Higgs (2)

A famous (or perhaps very good looking) physicist enters the room.

He immediately attracts a group of admirers. A local distortion of the field is generated and propagates.

how do elementary particles acquire mass higgs 3
How do Elementary Particles Acquire Mass? - Higgs (3)

It is getting ever more difficult for him to move.

He seems to gain mass. Just like a particle moving through the Higgs-field.

how do elementary particles acquire mass higgs 4
How do Elementary Particles Acquire Mass? - Higgs (4)

The same mechanism works for a simple message.

The buffet is open!

how do elementary particles acquire mass higgs 5
How do Elementary Particles Acquire Mass? - Higgs (5)

Again a distortion develops.

This is how the Higgs particle itself acquires its mass.

all particles of the standard model1
All Particles of the Standard Model

Crucial theoretical prediction

Evidence

slowly emerging

K.H. Meier

emmy amalia noether 1882 1935

wikipedia

Emmy AmaliaNoether (1882-1935)

All fine technical points aside, Noether\'s theorem can be stated informally

If a system has a continuous symmetry property, then there are corresponding quantities whose values are conserved in time.

time invariance -> energy conservation

translational invariance -> momentum conservation

rotational invariance -> angular momentum conservation

Symmetries appear to be a principle of nature

supersymmetry susy
Supersymmetry - SUSY

Standard Particles

SUSY Particles

The world as we know it

A whole new world?

dark matter
Dark Matter

Dark Matter interactsvia Gravitation. This leads togravitational lensing.

There are roughly 3000 invisible,

yet “tractable”, particles per

cubic meter of the universe.

all kinds of candidatesfor cold dark mattermay be produced at LHC

INVISIBLE!

summary
Summary
  • What is the nature of matter? concept of elementary constituents and their interactionsleads to proper description of processes in nature.
  • How do we study it?just like looking – by scattering of particles.
  • What are our (physicists’) physics concepts?detailed description in so-called quantum field theories.
  • If they appear to be abstract, how do we try to motivate, communicatethese concepts?does nature care?
  • Analogies – do you find them useful?
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