What IS Matter ? Matter is all the “stuff” around you! Here’s the picture we’re going to uncover (not all today though) Hadrons Matter Leptons Baryons Mesons Charged Neutrinos Forces Weak EM Strong Gravity Quarks Anti-Quarks Quarks Anti-Quarks

We’re going to work our way from the largest size objects which we know about to the smallest size objects which we know about

Where does all this come from? The universe is a very big place! It is filled with galaxies much like our own, the Milky Way There are likely ~100 billion of them which we can “see”. Each of these galaxies contain around 100 billion stars. Our Milky Way galaxy is simply one of them. Our Sun is just one of the 10,000,000,000,000,000,000,000 stars in the universe! Fig: Small section of the universe, from the Hubble Space Telescope (HST)

Our Galaxy: The Milky Way How big is the Milky Way (M.W.)? Its radius is about 100,000 light years ! How far is a light year (l.y.)? It’s the distance light travels in 1 year! Us (Our Solar System) So, 1 l.y. = 5,870,000,000,000 miles (5.9x10 12 mi.) ! So, the M.W. Galaxy radius is about 600,000,000,000,000,000 (6x10 17 ) miles in radius!

The Center of our Solar System: The Sun At the center of our solar system is our star, the Sun It’s diameter is ~100 times that of the earth, which implies you could fit ~1,000,000 earths inside the sun! It’s is ~330,000 times as massive as the Earth

The Sun (cont) It is a thermonuclear reactor. Inside the sun, hydrogen is being converted into helium. In this process, energy is released in the form of heat, electromagnetic waves (UV, visible light), neutrinos, etc. It’s surface temperature is ~10,000 O C; other parts of the sun can be as hot as 15,000,000 O C. So, it’s HOT !

Our Solar System: The Planets 3.6 billion miles Earth is at about 94 million miles from the Sun

The Planets Earth (Diam ~ mi.)  The figure shows relative sizes of the planets  Distances between planets not drawn to scale  Astronomically, we’re pretty tiny! Sun Jupiter Saturn Uranus Neptune Pluto 3.6 billion miles

The Earth Mass : 6 x [kg] Radius: 6.4 million meters Africa

Ahhh, and finally we’re back home  So, to set the scale:  From here to California 2,500 miles  From here to the next closest star 25,000,000,000,000 miles (25 trillion miles)  Like traveling back and forth to California 10 billion times Not very practical to get even to the next closest star!

Exercise The next closest star is about 25 trillion miles away. How long would it take an spacecraft moving at 20,000 miles/hr to get to this star? Well, every hour the spacecraft goes 20,000 miles (2x10 4 miles) So, the time it would take would be: (25 x [miles]) / 2x10 4 [miles/hr] = 1.25 billion hours = 52 million days = 143,000 years = 1,430 centuries!

And then there’s US !  We’re very small compared to the vast universe!  However, there are things which are a lot smaller than us.  Well, let’s keep going!

What are we made of ?  We’re made of cells which contain DNA. - Different cells serve different functions in your body.  Cells contain a nucleus, which holds your DNA !  And the DNA is simply a complex chain of molecules which contains your genetic code!  And what are molecules made of ? ”

The Elements  Molecules are complex structures of the elements

The Atom m (2 x m) 5x m Electrons Nucleus

Atoms and Space Approximately what fraction of the volume of an atom does the nucleus consume? Assume that the nucleus and the atom can be approximated via spheres with the radii given below? Use the following data. The radius of the nucleus is ~ 5x [m]. The electrons orbits at a radius of ~ 2x [m] Ignore the electrons size, as it is unimportant. The volume of a sphere is (4/3)  R 3.

Answer… a) First find the volume of the entire atom Volume = (4/3)*  2x ) 3 = 3.4 x [m 3 ] b) Now find the volume which contains the nucleus. Volume = (4/3)*  5x ) 3 = 5.2 x [m 3 ] c) Now compute the fraction: Fraction = (5.2 x / 3.4 x ) = In other words, more than % of an atom is empty space !!!

What’s in the Nucleus? Protons Neutrons Protons are positively charged and that amount of charge is exactly equal (and opposite) to the charge of the electron Neutrons are similar to protons (ie., similar mass), but have a net charge of zero. Recall: 1 [fm] = [m]

Are protons and neutrons fundamental? (By fundamental, I mean are they indivisible? The answer is NO ! Protons and neutrons are made of smaller objects called quarks! (1.6 x m) 1x m (at most)  Protons 2 “up” quarks 1 “down” quark  Neutrons 1 “up” quark 2 “down” quarks

Three Families of Quarks Generations IIIIII Charge = -1/3 d (down) s (strange) b (bottom) Charge = +2/3 u (up) c (charm) t (top) Also, each quark has a corresponding antiquark. The antiquarks have opposite charge to the quarks Woohhh, fractionally charged particles? Increasing mass

The 6 Quarks, when & where… QuarkDateWhere Mass [GeV/c 2 ] Comment up, down -- ~0.005, ~0.010 Constituents of hadrons, most prominently, proton and neutrons. strange1947-~0.2discovered in cosmic rays charm1974 SLAC/ BNL ~1.5 Discovered simultaneously in both pp and e + e - collisions. bottom1977 Fermi- lab ~4.5 Discovered in collisions of protons on nuclei top1995 Fermi- lab ~175Discovered in pp collisions

How do we know any of this?  Recall that high energy particles provide a way to probe, or “see” matter at the very smallest sizes. (Recall Electron microscope example).  Today, high energy accelerators produce energetic beams which allow us to probe matter at its most fundamental level.  As we go to higher energy particle collisions: 1) Wavelength probe is smaller  see finer detail 2) Can produce more massive objects, via E=mc 2

Major High Energy Physics Labs Fermilab SLAC KEK CERN DESY BNL CESR

Fermilab Accelerator (30 miles from Chicago) 1.25 miles Main Injector Tevatron Experimental areas Top Quark discovered here at FNAL in 1995.

“Typical” Particle Detector

Typical physicist colleagues! Don’t ask me what they’re doing !

Summary  Protons and neutrons are made of up & down quarks.  The strange quark was uncovered in cosmic rays via their “strange” behavior.  Today, accelerators produce high energy beams of particles which illuminate the structure of matter. * Smaller deBroglie wavelength  finer microscope * Can produce massive particles which haven’t been around since the Big Bang! (E=mc 2 )  The charm, bottom and top quarks were all discovered by producing them artificially at high energy accelerators.  Protons and neutrons are made of up & down quarks.  The strange quark was uncovered in cosmic rays via their “strange” behavior.  Today, accelerators produce high energy beams of particles which illuminate the structure of matter. * Smaller deBroglie wavelength  finer microscope * Can produce massive particles which haven’t been around since the Big Bang! (E=mc 2 )  The charm, bottom and top quarks were all discovered by producing them artificially at high energy accelerators.