Presentation on theme: "PUBLIC UNDERSTANDING OF SCIENCE"— Presentation transcript:
1 PUBLIC UNDERSTANDING OF SCIENCE W. G. SCOTTRAL/PPD24 Jan 2006PUBLIC UNDERSTANDING OF SCIENCEPPARC 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 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.
2 THE STANDARD MODEL: where: (schematic)higgskinetic termfermionkinetic termyukawatermgauge“kinetic” termwhere:“higgs potential”field-strength tensor“covariant derivative”vector potential
3 gives masses to the pointlike particles : THE HIGGS FIELD:quarksleptonsW,Z etc.gives masses to the pointlike particles :refraction?.
4 …but not to the neutron/proton! u=“UP” (+2/3)QUARKSd=“DOWN” (-1/3)
30 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 AREMIRROR REFLECTNS!!
31 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!
32 CLOSE TO THE HEART OF THE PROBLEM: How would you communicate left and right over the phone?
33 IT’S A RIGHT-HANDER’S WORLD SPIRAL STAIRCASE BUILT FOR DEFENDER WIELDING SWORD IN RIGHT HANDIN THE POPULATION AT LARGE:APPROX. 90% RIGHT-HANDEDAPPROX. 10% LEFT- HANDEDLATIN:DEXTRA = RIGHT (cf “DEXTROUS”)SINISTRA = LEFT (cf “SINISTER”)
35 MORE ABSTRACTLY z z x y y x RIGHT HANDED LEFT HANDED COORDINATE SYSTEM
36 MORE ABSTRACTLY z z x y y x RIGHT HANDED LEFT HANDED COORDINATE SYSTEM
37 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
38 OPTICAL ACTIVITY OPTICALLY ACTIVE SUBSTANCES ROTATE THE PLANE OF POLARISATION OF POLARISED LIGHT
40 Louis PasteurPateur felt that handedness could only be distinguished/separated by living things.
41 Names for clockwise and anticlockwise helices: 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 eyeAway from your eye
42 ALICE WAS RIGHT !!! “Perhaps looking glass milk isn’t good to drink” - Lewis Carroll, Alice through the looking glassALICE WAS RIGHT !!!
43 Fleming’s Left Hand Motor Rule: NOW FOR SOME A/S PHYSICSFleming’s Left Hand Motor Rule:IS THE PROBLEM SOLVED ?
44 We DO know the direction of the curremt +The positive terminal is connected to the central carbon rodThe negative terminal is connected to the zinc casing-Conventional Current flows from positive to negative (opposite to electron flow)
45 But do we REALLY know the Magnetic Field Direction? Yes, here on Earththe North Poleof a magnetpoints North!Problem Solved !?But you can’t be sure it is the same on another planet?Even the Earth’s field reverses sometimes
46 left/right convention to an alien living How would you radio ourleft/right convention to an alien livingon a distant galaxy?
47 We could set up our magnetic field using a 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 motionMagnetic field
48 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 !
49 DEFINING LEFT AND RIGHT ASOLUTELY WITH ELECTRO-MAGNETIC FORCES IS IMPOSSIBLE !!FLEMINGS LEFT-HAND RULE MERELY SWAPS THE LEFT/RIGHT PROBLEM FOR A NORTH/SOUTH PROBLEM WITH MAGNETS !MOST PHYSICISTS ASSUMED THAT AN ABSOLUTE DEFINITION OF LEFT AND RIGHT WAS COMPLETELY IMPOSSIBLE !!BUT IN 1956 THERE WAS THE SHOCKING DISCOVERY OF `PARITY VIOLATION’ BY THE `WEAK FORCE’ IN NUCLEAR BETA DECAY:
57 Neutrinos and Anti-neutrinos The weak interaction is a fundamental source of Left-Right asymmetry in nature
58 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.+Analysepolarisationof photonin comptonscattering
59 Co-60 expt. doesn’t solve matter vs. anti-matter! positrons (e+)neutrinosMagnetic fieldAnti-Mirror ExperimentOriginal Experimentelectrons (e-)anti-neutrinosMagnetic field
62 Summary Left & right hands are mirror reflections Mirrors invert front and backL/R convention not verbally communicanleLeft and right symmetry nearly perfect but broken by the weak interactionThe Cobalt-60 experiment can distinguish left and right (and so north and south poles)Neutrinos are left handed and anti-neutrinos are right handedAliens made of antimatter will get left and right wrong – so don’t get too close!!!!.zyx