what is matter ? matter is all the “stuff” around you! here’s the picture we’re going to...
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What IS Matter ?• Matter is all the “stuff” around you!
• Here’s the picture we’re going to uncover(not all today though)
HadronsHadrons
MatterMatter
LeptonsLeptons
BaryonsBaryons MesonsMesons ChargedCharged NeutrinosNeutrinos
ForcesForces
WeakWeak EMEM
StrongStrongGravityGravity
QuarksAnti-Quarks
QuarksAnti-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 likeour own, the Milky Way
There are likely ~100 billion of themwhich 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 SolarSystem)
So, 1 l.y. = 5,870,000,000,000 miles (5.9x1012 mi.) !
So, the M.W. Galaxy radius is about600,000,000,000,000,000 (6x1017) 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 OC; other parts of thesun can be as hot as 15,000,000 OC. So, it’s HOT !
Our Solar System: The Planets
3.6 billion milesEarth is at about 94 million miles
from the Sun
The Planets
Earth(Diam ~ 25000 mi.)
The figure shows relative sizes of the planets Distances between planets not drawn to scale Astronomically, we’re pretty tiny!
Sun Jupiter
SaturnUranus Neptune
Pluto
3.6 billion miles
The Earth
Mass : 6 x 1024 [kg]
Radius: 6.4 million meters
Africa
Ahhh, and finally we’re back home So, to set the scale:
From here to California2,500 miles
From here to the next closest star 25,000,000,000,000 miles
(25 trillion miles)
Like traveling back and forth toCalifornia 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 (2x104 miles)
So, the time it would take would be: (25 x 1012 [miles]) / 2x104 [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 tothe vast universe!
However, there are thingswhich are a lot smaller than us.
Well, let’s keep going!
What are we made of ?
We’re made of cells whichcontain 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 ? 0.0002”
The Elements Molecules are complex structures of the elements
The Atom
0.0000000002 m(2 x 10-10 m)
5x10-15 m
Electrons Nucleus
Atoms and SpaceApproximately what fraction of the volume of an atom does thenucleus 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 ~ 5x10-15 [m].
• The electrons orbits at a radius of ~ 2x10-10 [m]
• Ignore the electrons size, as it is unimportant.
• The volume of a sphere is (4/3)R3.
Answer…
a) First find the volume of the entire atomVolume = (4/3)*2x10-10)3 = 3.4 x 10-29 [m3]
b) Now find the volume which contains the nucleus.Volume = (4/3)*5x10-15)3 = 5.2 x 10-43 [m3]
c) Now compute the fraction:Fraction = (5.2 x 10-43 / 3.4 x 10-29 ) = 0.000000000000015
In other words, more than 99.99999999% of an atom is empty space !!!
What’s in the Nucleus?
ProtonsNeutrons
Protons arepositively chargedand that amountof charge is exactlyequal (and opposite)to the charge of theelectron
Neutrons are similar to protons(ie., similar mass), buthave a net charge ofzero.
Recall: 1 [fm] = 10-15 [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 10-15 m)
1x 10-18 m(at most) Protons
2 “up” quarks 1 “down” quark
Neutrons 1 “up” quark 2 “down” quarks
Three Families of Quarks
Generations
I II III
Charge =
-1/3d
(down)
s(strange)
b (bottom)
Charge =
+2/3u
(up)
c (charm)
t(top)
Also, each quark has a corresponding antiquark.The antiquarks have opposite charge to the quarks
Woohhh,fractionallychargedparticles?
Increasing mass
The 6 Quarks, when & where…
Quark Date WhereMass
[GeV/c2]Comment
up, down
- -~0.005, ~0.010
Constituents of hadrons, most prominently, proton and
neutrons.
strange 1947 - ~0.2 discovered in cosmic rays
charm 1974SLAC/
BNL~1.5
Discovered simultaneously in both pp and e+e- collisions.
bottom 1977Fermi-
lab~4.5
Discovered in collisions of protons on nuclei
top 1995Fermi-
lab~175 Discovered in pp collisions
How do we know
any of this?Recall that high energy particlesprovide a way to probe, or“see” matter at the very smallestsizes. (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 detail2) Can produce more massive objects, via E=mc2
Major High Energy Physics LabsFermilabFermilab
SLACSLAC
KEKKEKCERNCERN
DESYDESY
BNLBNL
CESRCESR
Fermilab Accelerator (30 miles from Chicago)
1.25 miles
Main Injector
Tevatron
Experimental areasExperimental areas
Top Quarkdiscovered here at FNALin 1995.
Top Quarkdiscovered here at FNALin 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=mc2)
The charm, bottom and top quarks were all discovered by producingthem 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=mc2)
The charm, bottom and top quarks were all discovered by producingthem artificially at high energy accelerators.