1938 when he premiered in comic book form Superman’ s flying was explained as jumping

1. 1938 when he premiered in comic book form Superman’s flying was explained as jumping with super strength.

2. TheAdventures of Superman(1950) Faster than a speeding bullet! More powerful than a locomotive! Able to leap tall buildings with a single bound!

4. The Superman movie (1978) included camera shots of stopping, hovering, surveying below before launching off in a new direction. What’s wrong with that?

5. When an object explodes or breaks apart:: Is this ever possible? In free space? Even in the initial moment along the ground? Why?

6. Explosion (inelasticun-collision) Before the explosion: Mass, M vo = 0 After the explosion: v1 v2 m2 m1

7. No external forces, so P is conserved. Initially:P = 0 Finally: P= m1v1+ m2v2= 0 m1v1 = - m2v2 v1 v2 m1 m2 Explosion... vo = 0

8. Before fission: Uranium nucleus After fission: 1 2 Which fragment has a greater momentum? A) 1 B) 2 C) both the same

9. Before fission: Uranium nucleus After fission: 1 2 Which fragment has a greater speed? A) 1 B) 2 C) both the same

10. Before fission: Uranium nucleus After fission: 1 2 Which fragment has a greater momentum? C) both the same speed? A) 1 Same momentem! Total momentum before fission is zero, so total after must still be zero (no external forces so momentum is conserved). Since momentum is a vector, fragments 1 and 2 must have equal and opposite momenta. Since fragment 1 has a smaller mass, it must have greater speed since v = p / m.

11. p = 0 pgas procket pi = 0 = pf = pgas + procket pgas = – procket pi = 0 = pf = prifle + pbullet prifle = – pbullet

12. A cannon rests on a railroad flatcar with a total mass of 1000 kg. When a 10 kg cannon ball is fired at a speed of 50 m/sec, as shown, what is the speed of the flatcar? A) 0 m/s B) ½ m/s to the right C) 1 m/s to the left D) 20 m/s to the right

13. ? A bomb at rest explodes into four fragments. The momentum vectors for three of the fragments are shown. Which arrow below best represents the momentum vector of the fourth fragment? C D A B

14. ? No external forces act on the bomb, so its momentum must be conserved: the total momentum before the explosion is zero, so total momentum after must also be zero. A B C D

15. An explosive charge separates rocket stages high in earth’s atmosphere. Which best represent the trajectories of the stages? A B C

16. An artillery shell bursts at the peak of its trajectory. Which best represents its streaming fragments? A B D C

17. For a particle decaying in flight would this pair of trajectories be possible? Why?

18. Status of particle physics early 20th century Electron J.J.Thomson 1898 nucleus ( proton) Ernest Rutherford 1908-09 a Henri Becquerel 1896 Ernest Rutherford 1899 b g P. Villard 1900 X-rays Wilhelm Roentgen 1895

19. Status of particle physics early 20th century Electron J.J.Thomson 1898 nucleus ( proton) Ernest Rutherford 1908-09 a Henri Becquerel 1896 Ernest Rutherford 1899 b g P. Villard 1900 X-rays Wilhelm Roentgen 1895

20. 1930 Series of studies ofnuclear beta decay, e.g., Potassium goes to calcium10K40 20Ca40 Copper goes to zinc29Cu64 30Zn64 Boron goes to carbon5B12  6C12 Tritium goes to helium1H3  2He3 1932 Once neutron discovered, included the more fundamental n  p + e For simple 2-bodydecay, conservation of energy and momentum demand both the recoil of the nucleus and energy of the emitted electron be fixed (by the energy released through the loss of mass) to a single precise value. Ee = (mA2 - mB2 - me2)c2/2mA but this only seems to match the maximum value observed on a spectrum of beta ray energies!

21. 1932n  p + e- + neutrino charge0 +1 -1 ? mass939.56563938.272310.51099906? MeV MeV MeV neutrino mass < 5.1 eV < me /100000  0

22. 1932 Carl Anderson first observes the positron in a cloud chamber photograph. • Droplet density (thickness) of track appears to • identify it as that of an electron • Curvature of track confirms the charge to mass • ratio (q/m) is that of an electron • The particle’s slowing in its passage through • lead foil establishes its direction ( UP! ). • Direction ofcurvatureclearly indicates it is • POSITVELYcharged!

23. Additional comments on Matter/Antimatter Production • Particles are created in pairs e+ and annihilate in pairs e+e- e- Notice how this “conserves” ELECTRIC CHARGE (as well as MOMENTUM and ENERGY) p+pp+p+p+p Center of Momentum frame Lab frame (fixed target) a c d b a b a b at threshold of production final state total energy = 4mprotonc2 Soconservationofenergyargues:EaCOM+EbCOM=4mc2

24. 1936 Millikan’s group shows at earth’s surface cosmic ray showers are dominated by electrons, gammas, and X-particles capable of penetrating deep underground (to lake bottom and deep tunnel experiments) and yielding isolated single cloud chamber tracks

25. 1937 Street and Stevenson • 1938 Andersonand Neddermeyer • determine X-particles • are charged • have 206× the electron’s mass • decay to electrons with • a mean lifetime of 2msec 0.000002 sec

26. 1947 Lattes, Muirhead, Occhialini and Powell observe pion decay 

27. 1947 Lattes, Muirhead, Occhialini and Powell observe pion decay Consistently ~600 microns (0.6 mm) 

28. Under the influence of a magnetic field m+ p+ m+ energy always predictably fixed by Ep

29. 1932 n  p + e- + neutrino charge 0 +1 -1 ? mass 939.56563 938.272310.51099906? MeV MeV MeV neutrino mass < 5.1 eV < me /100000  0 m+ m+ energy always predictably fixed by Ep simple 2-body decay! p+ ?? p+m+ + neutrino? charge +1 +1 ?

30. n p + e- + neutrino? p+m+ + neutrino? Then m-e- + neutrino? p ??? m e

31. n p + e- + neutrino? p+m+ + neutrino? Then m-e- + neutrino? p ??? m e As in the case of decaying radioactive isotopes, the electrons’s energy varied, with a maximum cutoff (whose value was the 2-body prediction) 3bodydecay! e m 2 neutrinos

32. Hadrons“heavy” or “strong” particles” p, n(the nucleons)and those they interacted “strongly” with Mesonsintermediate or medium mass  Leptons “light particles” e-, e+, , 

33. 1953, 1956, 1959Cowan & Reines Savannah River (1000-MWatt) Nuclear Reactor in South Carolina looked for the inverse of the process n p + e- + neutrino p + neutrino n + e+ with estimate flux of 51013 neutrinos/cm2-sec observed 2-3 p + neutrino events/hour also looked for n + neutrino p + e- but never observed!

34. 1953 Konopinski & Mahmoud introduce LEPTON NUMBER to account for which decays/reactions are possible, which not e,  ( )  assigned L = +1 e+, + ( +)  assigned L = -1 n p +e- + neutrino p + neutrino  n + e+

35. 1953 Konopinski & Mahmoud introduce LEPTON NUMBER to account for which decays/reactions are possible, which not e,  ( )  assigned L = +1 e+, + ( +)  assigned L = -1 n p +e- +  p +   n + e+

36. 1953 Konopinski & Mahmoud introduce LEPTON NUMBER to account for which decays/reactions are possible, which not e,  ( )  assigned L = +1 e+, + ( +)  assigned L = -1 n p +e- +  p +   n + e+ n +   p + e- ???

37. 1962 Lederman,Schwartz,Steinberger Brookhaven National Laboratory using a  as a source of  antineutrinos and a 44-footthick stack of steel (from a dismantled warship hull) to shield everything but the ’s found 29 instances of  + p  + + n but none of  + n  e+ + n

38. Elastic collision

40. p p p p p p

41. 1947 Rochester and Butler cloud chamber cosmic ray event of a neutral object decaying into two pions K0  + + 1949 C. F. Powell photographic emulsion event K+ + + 1950 Carl Anderson Cal Tech  p + 

42. 1952 Brookhaven Cosmotron 1st modern accelerator artificially creating these particles for study 1954 6.2-GeV p synchrotronLawrence,Berkeley 1960 28-GeV p synchrotronCERN, Geneva 33-GeV p synchrotronBrookhaven Lab 1962 6-GeV e synchrotron Cambridge 1963 12.5-GeV p synchrotronArgonne Lab 1964 6.5-GeV p synchrotron DESY,Germany 1966 21-GeV e LinacSLAC (Standford)