Presentation on theme: "PUBLIC UNDERSTANDING OF SCIENCE W. G. SCOTT RAL/PPD 24 Jan 2006 PPARC encourages us to spend 1% of our research grant funding on “outreach” activities,"— Presentation transcript:
PUBLIC UNDERSTANDING OF SCIENCE W. G. SCOTT RAL/PPD 24 Jan 2006 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 yr olds in schools etc. can help attract more young people into a scientific career. (e.g. RAL MasterClass Mar 2007). 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. Helps produce highly qualified researchers with advanced skills needed by academia, industry and commerce.
THE STANDARD MODEL: “higgs potential” fermion kinetic term gauge “kinetic” term yukawa term higgs kinetic term where: “covariant derivative” field-strength tensor vector potential (schematic)
THE HIGGS FIELD: gives masses to the pointlike particles : quarks leptons W,Z etc. refraction?.
u=“UP” (+2/3) PROTON NEUTRON d=“DOWN” (-1/3) QUARKS …but not to the neutron/proton!
ELECTRO-MAGNETIC INTERACTION A FEYNMAN DIAGRAM see “QED: the strange theory of light and matter”
QUARK CONFINEMENT The “Strong” Force Quark Antiquark
THE “COLOUR” FORCE
QCD gluons 8 colours quarks 3 colours
u e- d W+ WEAK INTERACTION
NEUTRAL CURRENTS (1973)
THE “FORCE” PARTICLES g 1 g 2 g 3 g 4 g 5 g 6 g 7 g 8 W - Z 0 W + γ
THE “MATTER” PARTICLES Q /3 +2/3
ELECTROWEAK TGCs e-e- e+e+ z0z0 w+w+ w-w-
see M. Gardner “The Ambidextrous Universe”
WHAT IS THE DIFFERENCE BETWEEN A LEFT AND A RIGHT HABD? RH IS BIGGER THAN LH ???
His right hand IS much bigger!
WHAT IS THE DIFFERENCE BETWEEN A LEFT AND A RIGHT HAND? RH IS BIGGER THAN LH ???. THUMBS ON OPPOSITE EDGES ? LH AND RH ARE MIRROR REFLECTNS!! OR PALMS ON OPPOSITE SIDES ?
WHY DOES A MIRROR REVERSE 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?
IT’S A RIGHT-HANDER’S WORLD LATIN: DEXTRA = RIGHT (cf “DEXTROUS”) SINISTRA = LEFT (cf “SINISTER”) SPIRAL STAIRCASE BUILT FOR DEFENDER WIELDING SWORD IN RIGHT HAND IN THE POPULATION AT LARGE: APPROX. 90% RIGHT-HANDED APPROX. 10% LEFT- HANDED
MORE ABSTRACTLY RIGHT HANDED COORDINATE SYSTEM LEFT HANDED COORDINATE SYSTEM y z x x z y
x y z Right Left MORE ABSTRACTLY RIGHT HANDED COORDINATE SYSTEM LEFT HANDED COORDINATE SYSTEM y z x x z y
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 OPTICALLY ACTIVE SUBSTANCES ROTATE THE PLANE OF POLARISATION OF POLARISED LIGHT
Double Refraction (in a Calcite Crystal)
Louis Pasteur 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
“Perhaps looking glass milk isn’t good to drink” - Lewis Carroll, Alice through the looking glass ALICE WAS RIGHT !!!
Fleming’s Left Hand Motor Rule: IS THE PROBLEM SOLVED ? NOW FOR SOME A/S PHYSICS
We DO know the 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 you can’t be sure it is the same on another planet? Even the Earth’s field reverses sometimes Yes, here on Earth the North Pole of a magnet points North! Problem Solved !?
We could set up our magnetic field using a current? Current Magnetic field 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
FLEMINGS LEFT-HAND RULE MERELY SWAPS THE LEFT/RIGHT PROBLEM FOR A NORTH/SOUTH PROBLEM WITH MAGNETS ! DEFINING LEFT AND RIGHT ABSOLUTELY WITH 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 ELECTRO-MAGNETIC FORCES IS IMPOSSIBLE !! BUT IN 1956 THERE WAS THE SHOCKING DISCOVERY OF `PARITY VIOLATION’ BY THE `WEAK FORCE’ IN NUCLEAR BETA DECAY: MOST PHYSICISTS ASSUMED THAT AN ABSOLUTE DEFINITION OF LEFT AND RIGHT WAS COMPLETELY IMPOSSIBLE !!
Beta Decay neutron
Beta Decay proton anti-neutrino electron
Feynman diagram for Beta Decay
N S NEUTRONS AND PROTONS IN NUCLEUS NET ROTATION = “CURRENT” NUCLEUS BEHAVES LIKE SMALL BAR MAGNET
Madame Wu Electrons Anti-neutrinos Magnetic field DISCOVERED “PARITY VIOLATION”
Cobalt-60 experiment solves the L/R problem! electrons (e - ) anti-neutrinos Magneti c field Original Experiment anti-neutrinos electrons (e) Magnetic field Mirror Experiment
Neutrinos and Anti-neutrinos The weak interaction is a fundamental source of Left-Right asymmetry in nature
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 +
Co-60 expt. doesn’t solve matter vs. anti-matter! electrons (e - ) anti-neutrinos Magneti c field Original Experiment positrons (e+) neutrinos Magnetic field Anti-Mirror Experiment
WHAT IF HE PUTS OUT HIS LEFT HAND ?
Nowadays of course... we measure CP violation!
₪ 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!!!!. Summary z y x