1. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays “If we knew what we were doing, it wouldn’t be called research” - Albert Einstein

2. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays

3. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays The Fantastic Four ® ©1996 Marvel Comics

4. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays

5. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays

6. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln Cosmic Rays at the Energy Frontier James W. Cronin, Thomas K. Gaisser and Simon P. Swordy Special issue Magnificent Cosmos March 1998

7. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays Bibliography Clay, Robert and Bruce Dawson, Cosmic Bullets (Addison-Wesley, Reading, Massachusetts, 1997) Friedlander, Michael W., Cosmic Rays (Harvard University Press, Cambridge, 1989) Hayakawa, Satio, Cosmic Ray Physics (Wiley-Interscience, New York, 1969) Rutherford, James, Gerald Holton & Fletcher Watson, The Project Physics Course (Holt, Rinehart and Winston, Inc., New York, 1970) with additional images from NASA’s archive at http://antwrp.gsfc.nasa.gov/astropix.html

8. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays + An electron and a proton are set free, near each other, deep in outer space. The electron moves towards the proton with A) constant velocity ( v  constant ) B) increasing velocity but constant acceleration ( a  constant ) C) increasing velocity and increasing acceleration

9. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays + An electron and a proton are set free, near each other, deep in outer space. The electron moves towards the proton with A) constant velocity ( v  constant ) B) increasing velocity but constant acceleration ( a  constant ) C) increasing velocity and increasing acceleration There is a net force on the electron due to the proton’s charge, so the electron accelerates (A is out). As the electron moves closer to the proton, the force it experiences grows stronger (Coulomb’s Law holds F  1/d 2 ). If the force becomes stronger, and the mass does not change, then Newton’s Second Law (F = ma or a = F/m) says that the acceleration increases. The answer to the question must be (C).

10. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays

11. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays

12. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays When two identical socks are removed from a clothes dryer, they will usually A) repel each other B) cling to each other C) no way to predictl

13. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays When two identical socks are removed from a clothes dryer, they will usually A) repel each other B) cling to each other C) no way to predictl If the socks have acquired a static charge, they will most likely have acquired charge of the same sign, and repel each other. What determines if a material picks up electrons is the property called electron affinity. The socks acquire their charge by coming into contact will all the other clothes in the dryer. If the socks come in contact with material of a higher electron affinity, the socks will give up electrons to that material. When they come into contact with materials with a lower electron affinity, they will acquire electrons. Both socks will thus acquire the same charge, for the most part. Of course, it is possible that in the random mixing of clothes in the dryer, one of the socks only comes into contact with materials which take electrons from it, and the other socks rubs against materials which give up electrons. The socks will then have opposite charges and attract. However, this is more unlikely. The answer is (A).

14. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays Moving charge by friction Some atoms/molecules attract electrons more strongly than others. Affinity: a natural liking or sympathy far: weaker attraction close: stronger attraction electron jumps Electron Affinity rabbit’s fur glass wool silk rubber hard plastic F  1d21d2 Different materials have different electrons affinities

15. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays fur plastic rod When fur is rubbed on a plastic rod, both acquire an equal but opposite charge. If the fur merely rests on top of the plastic, each will acquire equal and opposite charges. T) True. F) False. Friction is necessary to provide enough heat (energy) for electrons to jump from the fur to the plastic.

16. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays fur plastic rod When fur is rubbed on a plastic rod, both acquire an equal but opposite charge. If the fur merely rests on top of the plastic, each will acquire equal and opposite charges. T) True. F) False. Friction is necessary to provide enough heat (energy) for electrons to jump from the fur to the plastic. The answer is True. It is not necessary to rub the fur on the rod. If they simply come into contact with no motion between them, electrons will still jump from the plastic to the fur. Why, then, is the fur rubbed? Because the contact between the plastic and the fur is a bunch of random, jagged edges. (Remember friction!) In the figure above, there are only about three contact points where the atoms are close enough for the electrons to make the jump. If instead the fur and plastic are rubbed, many, many more atoms come into contact with each other and more electrons can make the big move. The plastic and fur thus acquire more charge, which makes it more noticeable. plastic fur

17. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays Far apart: electrons stay with their own atoms  both atoms neutral Close: difference in electron affinity. Electron jumps. Move apart:electron stays with the atom it jumped to  both atoms charged electron Note: only contact between atoms is necessary. The heat of friction plays no role.

18. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays 1900 While studying atmospheric electricity, J. Estler and H. Geitel note an unknown, but continuously present source of ions “in the air” Charles T. R. Wilson’s ionization chamber Electroscopes eventually discharge even when all known causes are removed, i.e., even when electroscopes are sealed airtight flushed with dry, dust-free filtered air far removed from any radioactive samples shielded with 2 inches of lead seemed to indicate an unknown radiation with greater penetrability than x-rays or radioactive  rays Speculating they might be extraterrestrial, Wilson ran underground tests at night in the Scottish railway, but observed no change in the discharging rate.

19. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays 1909 Jesuit priest, Father Thomas Wulf, improved the ionization chamber with a design planned specifically for high altitude balloon flights. A taut wire pair replaced the gold leaf. This basic design became the pocket dosimeter carried to record one’s total exposure to ionizing radiation. Taking it first to the top of the Eiffel Tower (275 m) Wulf observed a 64% drop in the discharge rate. Familiar with the penetrability of radioactive  rays, Wulf expected any ionizing effects due to natural radiation from the ground, would have been heavily absorbed by the “shielding” layers of air.

20. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity. Wrapped photographic plate showed clear silhouettes, when developed, of the uranium salt samples stored atop it. 1896 While studying the photographic images of various fluorescent and phosphorescent materials, Becquerel finds potassium-uranyl sulfate spontaneously emits radiation capable of penetrating thick opaque black paper aluminum plates copper plates Exhibited by all known compounds of uranium (phosphorescent or not) and metallic uranium itself.

21. The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln A History of Cosmic Rays 1898 Marie Curie discovers thorium ( 90 Th) Together Pierre and Marie Curie discover polonium ( 84 Po) and radium ( 88 Ra) 1899 Ernest Rutherford identifies 2 distinct kinds of rays emitted by uranium:  - highly ionizing, but completely absorbed by 0.006 cm aluminum foil or a few cm of air  - less ionizing, but penetrate many meters of air or up to a cm of aluminum. 1900 P. Villard finds in addition to  rays, radium emits  - the least ionizing, but capable of penetrating many cm of lead, several feet of concrete