Head for Understandable Description of Matter and Forces at the Most Fundamental Level

1. N Head for Understandable Description of Matter and Forces at the Most Fundamental Level Frank Sciulli - Lecture I

2. N Particles and Forces tell us about the beginning of the Universe Frank Sciulli - Lecture I

3. Is this a Belief System? NO! Science does use the beauty of ideas, but ultimately relies on EXPERIMENT!! Frank Sciulli - Lecture I

4. Illustrate, hopefully, that Physics (Science) has as ultimate arbitrator NATURE ! ! ! ! Four Lectures Leading to the Standard Model of Particle Physics - A Paradigm • Particles, Light, and Special Relativity • Quantum Mechanics, Atoms and Particles • Particles, Forces, and the Electroweak Interaction • Hadrons, Strong Force and the Standard Model Frank Sciulli - Lecture I

5. Approach to the Subjects Eclectic: factual, historical, experimental, … Lets start with pre-20th Century • Newton’s Laws (Galileo,…) • Energy and Work • Thermodynamics • Chemistry … atoms? • Optics, fluids, waves, ... Particles and Forces: Frank Sciulli - Lecture I

6. Single slit Double slit Classical particles and waves Water waves hit slits Classical particle scattering (balls) Frank Sciulli - Lecture I

7. Forces from elsewhere Gravity, electricity, magnetism, …. Newton’s Laws for Particles Frank Sciulli - Lecture I

8. Consolidation of Electricity and Magnetism by Maxwell (1864) Established clear rules for fields as the origin of EM force. Made rules consistent! They read Source of E is charge (Gauss Law) No magnetic charge Faraday’s Law of Induction Source of B is charge motion + Maxwell’s new Displacement Current Frank Sciulli - Lecture I

9. Implications: Electromagnetic Waves Frank Sciulli - Lecture I

10. Observer sees fringes (light and dark pattern), corresponding to constructive and destructive interference: For example, if 2d2 -2d1 changes by /2, fringe pattern shifts Michaelson Interferometer Became important element in central problem of 100 yrs ago: why is Frank Sciulli - Lecture I

11. But the velocity of the mechanical wave relative to the observer obeys the same rules as a travelling particle: relative velocities Light also has velocity independent of source speed PROBLEMVelocity of a mechanical wave depends only on the medium, not the velocity of the source (even though frequency and wavelength change - Doppler shift) Example, it is possible for a “listener” to travel faster than a sound wave. In this case, the sound will never catch up to the listener. Sound wave in “A” never catches “B” if v>c But MEs state EM waves have v=c Frank Sciulli - Lecture I

12. V=30km/s Earth motion around sun • Essential element of scientific hypothesis: provides a possibility for testing! Most obvious resolution:Luminiferous Ether • Provides transmission medium, in analogy with that required by mechanical waves • Provides a “special” frame of motion … where the laws of E&M (Maxwell’s Equations) are valid • All other frames of reference (in motion relative to the special one), Maxwell’s Equations are only approximately true! Frank Sciulli - Lecture I

13. 1887: Michaelson-Morley idea Frank Sciulli - Lecture I

14. Apparatus on bed of liquid mercury, rotate by 90 degrees Michaelson - Morley Expt Use velocity of Earth around the sun v =30km/s Rotate apparatus by 90 deg… change in relative phase of the two light rays by  is expected Frank Sciulli - Lecture I

15. Earth motion around sun V=30km/s   5 10-7 m Make d as large as possible Michaelson Morley Experiment - “Big” Physics of 1887 CONCLUDE: No phase shift was observed NO ETHER … ?!%* Frank Sciulli - Lecture I

16. Plane shoots rocket Plane shoots laser Einstein’s Reasoning Maxwell’s Equations (eg Law of Induction at left) do not depend on which is moving relative to what. So it is reasonable that the value of c coming out of the equations should not depend on state of motion of anyone! Sound a bit crazy? Not to Albert Einstein! Newtonian mechanics with objects or (mechanical) waves: velocity is relative to motion of observer! OLDTHINK… Frank Sciulli - Lecture I

17. ConundrumEITHER light is like mechanical waves: E&M only valid in one frame!?OR light is NOT like mechanical waves; E&M valid in all frames, independent of their motionEinstein chose the latter Einstein “Laws of Physics the same in all inertial frames” MEANS Maxwell’s equations valid in all non-accelerating coord. systs BUT this implies that velocity of light = c in vacuum no matter where the light comes from and how fast you are moving Frank Sciulli - Lecture I

18. Einstein Postulates (1905) require(a) speed of light (in vacuum) same in all inertial frames(b) speed of light (in vacuum) independent of the motion of sourceCARRY MANY IMPLICATIONS Lorentz Contraction + Time Dilation + Frank Sciulli - Lecture I

19. Transformations of Position and Time Frank Sciulli - Lecture I

20. Reversible Check if these equations give correct answer: For x’=ct’ ….. x=ct ? Frank Sciulli - Lecture I

21. v << c = v/c Limiting cases So this  is essentially ONE unless the object is near the velocity of light… where it rises very rapidly. Frank Sciulli - Lecture I

22. Time Dilation and Lorentz Contraction Happening in S’ at x’=0 over t’ Rod at rest in S’, with length L0 Length in S is L, measure ends at same time: t=0 Frank Sciulli - Lecture I

23. Relativistic Invariants Frank Sciulli - Lecture I

24. Implications of Relativity for Particle Momentum and Energy Relativistic Nonrelativistic Implication: Matter is a form of energy. At v=0, E=mc2. Frank Sciulli - Lecture I

25. Transformation of Momenta/Energy Frank Sciulli - Lecture I

26. X X eV eV/c eV/c2 MeV MeV/c MeV/c2 GeV GeV/c GeV/c2 Energy/Momentum/Mass and Units Universal energy units are joules (traditionally); but a much simpler one for dealing with particles: (with electric charges that are multiples of the electron) Frank Sciulli - Lecture I

27. N Mass is Energy and vice versa • Macroscopic systems, mass stays essentially the same and • kinetic energies small compared to rest mass energy: separate! • Microscopic systems (atoms), energies of electrons are small • compared to mass of system: • in hydrogen atom, U=13.6 eV but M~109 eV/c2 • Note that mass of proton is ~ 1 GeV/c2 • Ultra - microscopic systems (nuclei and smaller), energies of • constituents get comparable or larger than their rest mass What about EM fields? Frank Sciulli - Lecture I

28. N Mass Disappears-Energy AppearsFUSION Mass difference of .0304u = 28.3 MeV/c2 becomes energy Frank Sciulli - Lecture I

29. Relativity is the way the world works Example: NAVSTAR Satellite system to track velocity of airplanes uses Doppler shifts. If non-relativistic Doppler formula were used, precision on velocity would be about 21 cm/s. If relativistic Doppler formula used, precision  1.4 cm/s Examples: Real-life everyday observations in particle and nuclear physics, where new matter is made and it spontaneously decays Frank Sciulli - Lecture I

30. Characterized by lifetime () or half-life (T1/2 =  ln2 = 0.7 ) 1000 100 10 1 Metastable Matter(Radioactive Decay makes a clock) Example 128I nuclide with T1/2 = 25 minutes. Compare: 14C has T1/2 = 5730 yrs.  has T1/2= 3.75  10-8 sec Frank Sciulli - Lecture I

31. N Working with Unstable Matter Can Make for Problems! Just kidding … It’s actually not that hard! Here we use pions, unstable particles with mass of 140 Mev and lifetimes of ~ 3 10-8 sec Frank Sciulli - Lecture I

32. 15 story high rise Four mile circumference Tevatron Ring Real World Test of Relativity: Fermilab Complex Frank Sciulli - Lecture I

33. measure velocity = v/c Accelerators Raise Kinetic Energy using Electric Fields Each loop, the energy of protons are raised by increment determined by electric potential: E =eV  = E/m Proton total Energy versus velocity Frank Sciulli - Lecture I

34. Beam protons hit stationary target (Et=m) with very large kinetic energy  = Eb/m Extracted protons have energy E  800 GeV Accelerated protons have very large energy What happens???? Frank Sciulli - Lecture I

35. Collision of 300 GeV proton with stationary nucleon New kinds of particles made out of kinetic energy: mesons (pions) with mass of 140 MeV each. Frank Sciulli - Lecture I

36.  Beams of pions made from collisions of high energy protons WRONG!! Beam line, 0.78 km long, transports 140 GeV ’s made at tgt Frank Sciulli - Lecture I

37. v  Right answer: Lab perspective Right!!! Frank Sciulli - Lecture I

38.  v Right answer: pion perspective Right!!! Frank Sciulli - Lecture I

39. Conclusions - Special Relativity • Relativity was required by experimental information at the time it was invented (1905) • It is essential now to describe the world, especially since we can directly observe objects travelling near the speed of light • The rules are, in fact, simple - see handout or website! • Do the problems and prove the simplicity! Frank Sciulli - Lecture I