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W. G. SCOTT RAL/PPD 24 Jan 2006. PUBLIC UNDERSTANDING OF SCIENCE.

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W. G. SCOTT

RAL/PPD

24 Jan 2006

PUBLIC UNDERSTANDING OF SCIENCE

PPARC encourages us to spend 1% of our research grant funding on “outreach” activities, promoting understanding, appreciation and awareness of our science to the general public:

Targeting 11-16 yr olds in schools etc. can help attract more young people into a scientific career. (e.g. RAL MasterClass 14-16 Mar 2007).

Helps produce highly qualified researchers with advanced skills needed by academia, industry and commerce.

Helps ensure that the UKs front line contribution in this science is recognised by opinion formers, decision-takers/politicians.

Taxpayers can have an appreciation and awareness of the research being funded on their behalf.


THE STANDARD MODEL:

(schematic)

higgs

kinetic term

yukawa

term

fermion

kinetic term

gauge

“kinetic” term

where:

“higgs potential”

field-strength tensor

“covariant derivative”

vector potential


THE HIGGS FIELD:

quarks

leptons

W,Z etc.

gives masses to the pointlike particles :

refraction?.


…but not to the neutron/proton!

PROTON

NEUTRON

u=“UP” (+2/3)

QUARKS

d=“DOWN” (-1/3)


ELECTRO-MAGNETIC INTERACTION

see “QED: the

strange theory of

light and matter”

A FEYNMAN DIAGRAM


QUARK CONFINEMENT

The “Strong” Force

Quark

Antiquark



“CHROMOSTATICS”

THE “COLOUR” FORCE


QCD

quarks

3 colours

gluons

8 colours


WEAK INTERACTION

u

e-

W+

d




THE “FORCE” PARTICLES

g1 g2 g3 g4 g5 g6 g7 g8W- Z0 W+γ



THE “MATTER” PARTICLES

Q -1 0

-1/3 +2/3


ELECTROWEAK TGCs

w+

w-

z0

e+

e-


see M. Gardner

“The Ambidextrous Universe”

The Left-Right

Problem




WHAT IS THE DIFFERENCE BETWEEN A LEFT AND A RIGHT HAND?

  • RH IS BIGGER THAN LH ???.

  • THUMBS ON OPPOSITE EDGES ?

  • OR PALMS ON OPPOSITE SIDES ?

LH AND RH ARE

MIRROR REFLECTNS!!


Why does a mirror reverse left and right but not up and down
WHY DOES A MIRRORREVERSE LEFT AND RIGHT BUT NOT UP AND DOWN?

  • A CONFUSING QUESTION !!!

  • SURELY IT REVERSES FRONT AND BACK ?

  • BUT IT DOES SEEM TO CHANGE RH TO LH!


Close to the heart of the problem how would you communicate left and right over the phone
CLOSE TO THE HEART OF THE PROBLEM:How would you communicate left and right over the phone?


IT’S A RIGHT-HANDER’S WORLD

SPIRAL STAIRCASE BUILT FOR DEFENDER WIELDING SWORD IN RIGHT HAND

IN THE POPULATION AT LARGE:

APPROX. 90% RIGHT-HANDED

APPROX. 10% LEFT- HANDED

LATIN:

DEXTRA = RIGHT (cf “DEXTROUS”)

SINISTRA = LEFT (cf “SINISTER”)



z

z

y

x

x

y

MORE ABSTRACTLY

LEFT HANDED

COORDINATE SYSTEM

RIGHT HANDED

COORDINATE SYSTEM


z

z

y

x

x

y

MORE ABSTRACTLY

LEFT HANDED

COORDINATE SYSTEM

RIGHT HANDED

COORDINATE SYSTEM

z

y

x

Left

Right


A molecule that, like your hands, cannot be made to look like its mirror-image by rotating it or displacing it, is called chiral.

This group of atoms is IN FRONT here, but goes BEHIND in the rotating reflection


OPTICAL ACTIVITY like its mirror-image by rotating it or displacing it, is called

OPTICALLY ACTIVE SUBSTANCES ROTATE THE

PLANE OF POLARISATION OF POLARISED LIGHT


Double refraction in a calcite crystal
Double Refraction like its mirror-image by rotating it or displacing it, is called (in a Calcite Crystal)


Louis pasteur
Louis Pasteur like its mirror-image by rotating it or displacing it, is called

Pateur felt that handedness could only be distinguished/separated by living things.


The DNA structure is a double helix looking something like a twisted ladder.

The two cross-linked helices are always right-handed, twisting in the same direction as a normal screw.

Names for clockwise and anticlockwise helices:

Away from your eye

Away from your eye


“Perhaps looking glass milk isn’t good to drink” twisted ladder.

- Lewis Carroll, Alice through the looking glass

ALICE WAS RIGHT !!!


Fleming s left hand motor rule
Fleming’s Left Hand Motor Rule: twisted ladder.

NOW FOR SOME A/S PHYSICS

IS THE PROBLEM SOLVED ?


We do know the direction of the curremt
We DO know the twisted ladder.direction of the curremt

+

The positive terminal is connected to the central carbon rod

The negative terminal is connected to the zinc casing

-

Conventional Current flows from positive to negative (opposite to electron flow)


But do we really know the magnetic field direction
But do we REALLY know the twisted ladder.Magnetic Field Direction?

Yes, here on Earth

the North Pole

of a magnet

points North!

Problem Solved !?

But you can’t be sure it is the same on another planet?

Even the Earth’s field reverses sometimes


How would you radio our twisted ladder.

left/right convention to an alien living

on a distant galaxy?


We could set up our magnetic field using a current
We could set up our magnetic twisted ladder.field using a current?

Current

RIGHT HAND GRIP RULE:

But applying a right hand rule followed by a left hand rule is equivalent to no handed rule at all.

i.e. The wrong hand used for the grip rule followed by the wrong hand used for the motor rule produces the same predicted motion

Magnetic field


DEFINING LEFT AND RIGHT ABSOLUTELY WITH twisted ladder.

ELECTRO-MAGNETIC FORCES IS IMPOSSIBLE !!

FLEMINGS LEFT-HAND RULE MERELY SWAPS THE LEFT/RIGHT PROBLEM FOR A NORTH/SOUTH PROBLEM WITH MAGNETS !


DEFINING LEFT AND RIGHT ASOLUTELY WITH twisted ladder.

ELECTRO-MAGNETIC FORCES IS IMPOSSIBLE !!

MOST PHYSICISTS ASSUMED THAT AN ABSOLUTE DEFINITION OF LEFT AND RIGHT WAS COMPLETELY IMPOSSIBLE !!

FLEMINGS LEFT-HAND RULE MERELY SWAPS THE LEFT/RIGHT PROBLEM FOR A NORTH/SOUTH PROBLEM WITH MAGNETS !

BUT IN 1956 THERE WAS THE SHOCKING DISCOVERY OF `PARITY VIOLATION’ BY THE `WEAK FORCE’ IN NUCLEAR BETA DECAY:


Beta decay
Beta Decay twisted ladder.

neutron


Beta decay1

proton twisted ladder.

electron

anti-neutrino

Beta Decay



NEUTRONS AND PROTONS IN NUCLEUS twisted ladder.

N

NET ROTATION

=

“CURRENT”

NUCLEUS

BEHAVES LIKE

SMALL BAR MAGNET

S


DISCOVERED twisted ladder.

“PARITY VIOLATION”

Anti-neutrinos

Magnetic field

Electrons

Madame Wu


Mirror Experiment twisted ladder.

anti-neutrinos

electrons (e)

Magnetic field

anti-neutrinos

electrons (e-)

Magnetic field

Cobalt-60 experiment solves the L/R problem!

Original Experiment


Neutrinos and anti neutrinos
Neutrinos and Anti-neutrinos twisted ladder.

The weak interaction is a fundamental source of Left-Right asymmetry in nature


Proving a neutrino is left handed goldhaber s experiment

+ twisted ladder.

Proving a neutrino is left-handed (Goldhaber’s Experiment)

  • An Eu atom takes in an electron which reacts with a proton to form a neutron.

  • Both a neutrino and a gamma ray are released.

  • The “handed-ness” of the gamma ray and the neutrino are the same due to angular momentum because they are emitted in opposite directions.

  • The photon in the gamma ray emitted was shown to be left-handed (using compton scattering), proving that the neutrino is also left-handed.

Analyse

polarisation

of photon

in compton

scattering


Anti-Mirror Experiment twisted ladder.

anti-neutrinos

neutrinos

Magnetic field

positrons (e+)

electrons (e-)

Magnetic field

Co-60 expt. doesn’t solve matter vs. anti-matter!

Original Experiment



we measure twisted ladder.

CP violation!

Nowadays of course . . .


Summary

z twisted ladder.

y

x

Summary

  • Left & right hands are mirror reflections

  • Mirrors invert front and back

  • L/R convention not verbally communicanle

  • Left and right symmetry nearly perfect but broken by the weak interaction

  • The Cobalt-60 experiment can distinguish left and right (and so north and south poles)

  • Neutrinos are left handed and anti-neutrinos are right handed

  • Aliens made of antimatter will get left and right wrong – so don’t get too close!!!!.


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