PHY313 - CEI544 The Mystery of Matter From Quarks to the Cosmos Fall 2005

Transcription

1 PHY313 - CEI544 The Mystery of Matter From Quarks to the Cosmos Fall 2005 Peter Paul Office Physics D then click on PHY313 or CEI544 Peter Paul 09/1/05 PHY313-CEI544 Fall-05 1

2 The Mystery of Matter: The Course The Goal: To understand at a conceptual level the current knowledge about the origin and forms of matter, the basic building blocks of nature and what holds them together. the appearance of matter in the Universe and its evolution. the open issues and the plans to resolve them: The big facilities the spin-offs and benefits to society derived from the quest to understand Matter. Peter Paul 09/1/05 PHY313-CEI544 Fall-05 2

3 Is Science incomprehensible, except to scientists? The answer is emphatically NO Example: Music is based on strict laws of harmony that govern composition, just like science is based on strict laws. Few people, except the trained experts understand these laws. But all people can tell whether music is harmonious or not, and can enjoy its beauty. Similarly, everybody can appreciate the beauty of the laws of physics, without needing details Peter Paul 09/1/05 PHY313-CEI544 Fall-05 3

4 Can we afford to have Two Languages? A car needs to stop rapidly. The deceleration is a. The scientist sees a force F that wants to smash the driver (mass m) into the windshield. Newton's law: F = m a From the law we learn that it is the deceleration, not the speed that determines the force. Thus use of a seatbelt is important even at low car velocity to counteract this force. The non-scientist can understand this and that is important for him/her, if we use the language by which we all communicate. Racing car or land yacht: It s the deceleration that counts for the seat belts. Peter Paul 09/1/05 PHY313-CEI544 Fall-05 4

5 Can Nature be dissected and explained by its parts? Model of a proton: Contains 3 quarks Structure of a Ribosome: It contains 50 different proteins 3 Transfer RNA s (red, blue and green) It contains billions of protons Can we compute the Ribosome structure if we understand the proton? Probably NOT Peter Paul 09/1/05 PHY313-CEI544 Fall-05 5

6 The Process The Course will.. be web based: Here is how to go to the web page: All lecture notes will be posted on the web site after the lecture There will be 6 homework problems each week, due the next week, based strictly on material covered each week. The grade will be based on that homework with an optional final for extra credit Answer the home work in brief words. Do not copy the lecture notes There will be a site visit to BNL for extra credit during one of the lecture periods Peter Paul 09/1/05 PHY313-CEI544 Fall-05 6

7 Visit to BNL on November 3, 2005 The Goal: To visit the RHIC accelerator and its two large detectors, STAR & PHENIX The relativistic heavy ion collider uses heavy ion collisions to recreate the universe as it existed ~ 1 µs after the Big Bang The tour buses(free) will start here at the beginning of the class and will return by the end of the class. Participation will be optional with extra credit for attendance Registration two weeks before. see The STAR Detector at RHIC Peter Paul 09/1/05 PHY313-CEI544 Fall-05 7

8 Brookhaven National Laboratory Peter Paul 09/1/05 PHY313-CEI544 Fall-05 8

9 The View in 1898: Physics is complete THEN CAME THE REVOLUTION Peter Paul 09/1/05 PHY313-CEI544 Fall-05 9

10 The State of Physics at the End of 1900 Newton invents mechanics Maxwell completes electrodynamics Light is just an EM wave Incorporates Optics into EM Helmholtz & Boltzmann complete thermodynamics Then Planck discovers energy quantization Einstein sees the connections between these fields, before Quantum mechanics was developed. MECHANICS THERMO- DYNAMICS ENERGY QUANTIZATION ELECTRO- DYNAMICS OPTICS Peter Paul 09/1/05 PHY313-CEI544 Fall-05 10

11 1905: The Year of Albert Einstein In 1905 Einstein produced 3 break-through papers: 1. Photoelectric effect: Light is an energy quantum that can be treated like a particle. E = h ν 2. Brownian motion: heat is kinetic energy of small particles moving in a medium: 3. Special Relativity: The speed of light must be the same in all inertial reference frame: E = mc 2 4. His Gedanken Experiments established a whole new way to gain physical insight Peter Paul 09/1/05 PHY313-CEI544 Fall-05 11

12 It all started with Roentgen He showed that we could see things with detectors other than our human eyes. Peter Paul 09/1/05 PHY313-CEI544 Fall-05 12

13 The Discovery of Radioactivity Henri Becquerel: (Accidental) Discovery of Radioactivity from uranium in 1896: Nobel Prize in Peter Paul 09/1/05 PHY313-CEI544 Fall-05 13

14 The Details of Radioactive Decay law Marie and Pierre Curie Nobel prize in 1903 No knowledge of Nuclei yet!! Radioactivity decreases exponentially with time Half life: The time it takes for half of the original radioactivity to decay. That means that any radioactivity initially present is never completely dead : Quite different from people s life. Each radioactive element has its own characteristic half life. Peter Paul 09/1/05 PHY313-CEI544 Fall-05 14

15 Electromagnetic Waves demonstrated Heinrich Hertz demonstrated in 1885 to 1890 that Electromagnetic Waves could be produced and traveled with the speed of light 3 x m/s This was the beginning of the communication revolution The EM waves had been predicted in 1884 by James Maxwell Peter Paul 09/1/05 PHY313-CEI544 Fall-05 15

16 Electromagnetic waves and length scales Electromagnetic waves have a wave length that ranges over many orders of magnitude. The longest distances are usually expressed in light-years. This is the distance that a flash of light would travel in one year. The speed of light is very fast: 8 c = m / s 300,000km / This is a very large distance. Calculate it as part of the Homework. s Peter Paul 09/1/05 PHY313-CEI544 Fall-05 16

17 Peter Paul 09/1/05 PHY313-CEI544 Fall-05 17

18 Max Planck then made the big step His analysis of electromagnetic waves trapped in a cavity led to the conjecture that Energy was quantized, i.e. came in chunks. This was a phenomenal abstraction because it could not be observed directly! To our eyes light does not seem to come in little flashes. This is because the Planck energy quantum is a very small chunk. 1 W of visible light contains quanta each second! One quantum of visible light is Peter Paul 09/1/05 PHY313-CEI544 Fall-05 18

19 The Scales of Physics This means in clear English that the scales and times of our daily experience are not adequate to understand science Modern physics aims to connect the smallest and the largest objects, the proton and the structures in the Universe. Peter Paul 09/1/05 PHY313-CEI544 Fall-05 19

20 The Nomenclature of Dimensions Prefixes that define powers of ten Fraction Prefix Symbol Multiple Prefix Symbol 10E(-18) atto a 10E(3) kilo k 10E(-15) femto f 10E(6) Mega M 10E(-12) pico p 10E(9) Giga G 10E(-9) nano n 10E(12) Tera T 10E(-6) micro µ 10E(15) Peta P 10E(-3) milli m 1 10E(18) Exa E Peter Paul 09/1/05 PHY313-CEI544 Fall-05 20

21 The Scales of Nature s.html The Planck Scales as the ultimate for our current theory in the Universe: T Pl = (G h/c 5 ) 1/2 Planck Length = 1.6 x cm Planck Time = 5.4 x s Planck Energy = 1.2 x GeV G = gravitational constant 6.67 x N m 2 /kg 2 Peter Paul 09/1/05 PHY313-CEI544 Fall-05 21

22 The Scale of Things Things Natural 10-2 m 1 cm 10 mm Nanometers and More Things Manmade Head of a pin 1-2 mm The Challenge Ant ~ 5 mm 10-3 m 1,000,000 nanometers = 1 millimeter (mm) Dust mite 200 µm Human hair ~ µm wide Red blood cells (~7-8 µm) ~10 nm diameter Fly ash ~ µm ATP synthesis 10-4 m Microworl d 10-5 m 10-6 m 10-7 m Nanoworl d 10-8 m Ultraviolet Visible Infrared Microwave 0.1 mm 100 µm 0.01 mm 10 µm 1,000 nanometers = 1 micrometer (µm) 0.1 µm 100 nm 0.01 µm 10 nm Pollen grain Red blood cells Zone plate x-ray lens Outer ring spacing ~35 nm Self-assembled, Nature-inspired structure Many 10s of nm MicroElectroMechanical (MEMS) devices µm wide Nanotube electrode O O S O O O O O O O O O O O S O S O S O S P O O Fabricate and combine nanoscale building blocks to make useful devices, e.g., a photosynthetic reaction center with integral semiconductor storage. O O S O O S O S DNA ~2-1/2 nm diameter Peter Paul 09/1/05 PHY313-CEI544 Fall Atoms of silicon spacing ~tenths of nm 10-9 m m Soft x-ray 1 nanometer (nm) 0.1 nm Quantum corral of 48 iron atoms on copper surface positioned one at a time with an STM tip Corral diameter 14 nm Carbon buckyball ~1 nm diameter Carbon nanotube ~1.3 nm diameter Office of Basic Energy Sciences Office of Science, U.S. DOE Version , pmd

23 Planck s Constant h The two most important constants in Nature are: The speed of light c C = x 10 8 m/s Planck s constant h h = x J s or x ev s h is a very small amount of action h c = 1240 ev nm Relativity becomes important when velocity ~ c Quantum effects become important when energy x size ~ h c Example from chip design: Energy scale ~ 3 ev Size ~ 1240/3 nm = 400 nm This is a very practical dimension! Peter Paul 09/1/05 PHY313-CEI544 Fall-05 23

24 The Energy Scale of Matter ses/glossary/key_energies.html Energy units in the standard system is the Joule, 1 W = 1 J/s In advanced physics the energy unit is the ev, the energy it takes to accelerate one electric charge with a potential of 1 Volt. This unit is very small 1 ev = Joules 1000 ev = 1 kev 1 Million ev = 1 MeV 1 Billion ev = 1 GeV A 27-in TV accelerates electrons to 30 kev, The Relativistic Heavy Ion Collider accelerates Au ions to 100 GeV x 197 ~ 20 TeV about 1 Billion times your TV Peter Paul 09/1/05 PHY313-CEI544 Fall-05 24

25 Energy scale of microscopic matter Atoms ev to kev Materials 0.1 ev Nuclei MeV Elementary particles 100 MeV to GeV Largest existing accelerator (LHC) 16 TeV = 1.6 x 10 3 GeV Unification scale GeV Planck Energy 1.2 x GeV Thermal scales: Room temperature 1/40 ev Temperature of the sun surface 6000 degrees ~ 0.5 ev Temperature to melt nuclei 170 MeV = 2000 x Billions of the temperature at the surface of the sun Peter Paul 09/1/05 PHY313-CEI544 Fall-05 25

26 The Scale of the Fundamental Forces We know four fundamental forces. (There may exist a fifth) Interaction Relative Magnitude Range Action Strong force 10E(40) Very short Binds nuclei Electromagnetic force 10E(38) Very long Binds atoms and condensed matter Weak nuclear force 10E(15) Very short Produces beta decay Gravity 1 Very long Binds stellar systems Peter Paul 09/1/05 PHY313-CEI544 Fall-05 26

27 Some questions about fundamental forces Why is there such a mismatch in the range of the various forces? Why is there such a huge difference in the strengths of the different forces? Why are there 4 different forces, instead of just one? At sufficiently high energies they all come together But where is gravity? Peter Paul 09/1/05 PHY313-CEI544 Fall-05 27

28 What is Mass and where does it come from Mass defined by Newtons second law: Force = Mass x Acceleration M = F / a in kg units But a macroscopic body of mass M consists of many small pieces that can move around inside the body. Where do the little pieces get their mass from? LHC and RHIC will provide the answer for that. But what about the mass of the Universe; Where does it come from? Peter Paul 09/1/05 PHY313-CEI544 Fall-05 28

29 First Homework Set, due Sept. 8, Describe briefly the 3 important discoveries that Einstein published in Who demonstrated that electromagnetic waves exist. What lead to the discovery that light was an electromagnetic wave? 3. Where was Max Planck s office when he discovered his quantum theory? ((hint: go to the web!) 4. Give the approximate dimensions of the Earth, an ant, an atom and a nucleus, with their appropriate dimensional prefixes. 5. A light-year is a distance. How long is it? (hint: a year = 86,000 s) 6. Name the four forces that we encounter in Nature and describe briefly what action they perform. Peter Paul 09/1/05 PHY313-CEI544 Fall-05 29

30 How to submit Homework You must bring the homework to class before the due date It will be returned in class in the next lecture. I will personally grade the homework Do not submit homework electronically Be brief and to the point in your answers Peter Paul 09/1/05 PHY313-CEI544 Fall-05 30