What is fundamental? wwhat is it made of? whow is it all held together? The TWO most fundamental questions about the universe are: Fig. 15.1, p.

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1 What is fndamental? The TWO most fndamental qestions abot the niverse are: wwhat is it made of? whow is it all held together? Fig. 15.1, p. 467

2 For Fndamental Elements l The Hnt for the answers to those two qestions has been going on for a very long time. l It really started with the Greeks.

3 and Two Fndamental Forces There were two fndamental forces: Love Strife And World operates according to logos not mythos. This pictre is a tad too simple.

4 Let s jmp ahead 2000 years or so For fndamental forces (that we know abot): (1) strong (2) weak electrostatics electroweak (1970 s) (1700 s, 1800 s) magnetism (3) electromagnetic (4) gravity Increasing energy, decreasing time (back to the very early niverse)

5 What am I trying to do in my research? (1) strong GUT (2,3)electroweak TOE (4) gravity Big Bang

6 To do so takes big accelerators Fermilab, near Chicago CERN, near Geneva, Switzerland

7 Let s go back to electrostatics and ths back to the ancient Greeks The Greeks started the science of electrostatics (like almost everything else) they observed that when amber was rbbed, it wold attract small objects like feathers or straw s or like rbbing a balloon against yor shirt in fact or word for electricity comes from the Greek word for amber, electron

8 So not mch happened for 2000 years or so In the 16th centry, investigations revealed that there appeared to be two types of electricity vitreos: from rbbed glass, animal hair resinos: from rbbed amber, silk How is one different from the other? 2 bodies charged with vitreos electricity repel each other, as do 2 bodies charged with resinos electricity a body charged with resinos electricity will attract a body charged with vitreos Time ot for some demos

9 Is this the final story ( shold yo write down vitreos and resinos)? No and no In the mid-1700 s, Benjamin Franklin proposed what he called a one-flid theory of electricity. He proposed that every body had a normal amont of electricity. When a body is rbbed against another, some of the electricity is transferred from one body to another One body has an excess of electricity, the other a deficit He described the excess as having a + charge and the deficit a -charge

10 Can we stop now? Benjamin Franklin s theory was an advance bt not qite right In particlar his choice of signs will come back to hant s Let s review atomic strctre, the Solar System Model not qite right, bt it will do for now The ncles of the atom consists of protons + netrons Charge on proton = e = 1.6X10-19 C Each normal atom has as many electrons as protons Charge on electron = -e = - 1.6X10-19 C So every normal atom is netral

11 All electrical charges are mltiples of e The protons are stck inside the ncles The otermost electrons are the ones that can come off by rbbing i.e. electrostatic effects reslt from transfer of electrons and not of positive charges If otermost electrons are free to move within the material, we call the material a condctor If they re not free to move (bt can still be rbbed off), we call the material an inslator Third possibility is that a material can be a semi-condctor Now what happened with the glass rod, etc

12 Another way of extracting charges The van de Graf machine Has a belt which transfers charge to the metal dome Does it take electrons p to the dome or transfer electrons away from the dome?

13 Colomb s Law There is a force between 2 charges along the line joining them (a central force). The size of the force drops as 1/r 2 same sign charges repel opposite sign charges attract Where have we seen this before?

14 Gravity Both gravity and this electrostatic force we ve been discssing are central s this means we can define a type of fnction called a potential (later) vary as 1/r 2 Bt the electrostatic force is incredibly stronger than gravity

15 Comparison m 1 m 2 k = 9 X 10 9 N. m 2 /C 2 G = 6.67 X N. m 2 /kg 2 Force can be attractive or Force is always attractive replsive Consider the hydrogen atom

16 A brief smmary Stick to the SI system of nits and yo ll go far N(ewtons) for force m(eters) for distance kg for mass and now C(olombs) for electric charge and many other nits to come dring the semester