Transcript Document 7217621

Why Study Nature?
Power
(Control over it)
“When will the Nile
flood?”
(time/astronomy)
“What will make my
sick baby better?”
(medicine)
“How can I make my
spear fly faster and
farther?”
(physics)
Celebrity Status Because we
A-List parties
must.
Red carpet treatment
MTV interviews
Mankind has always
been driven to
understand the
world.
The world is
inherently simple
and beautiful. It
And always:
can be understood.
Babes…never forget
the babes…
As a single, unified thing there
exists in us both life and death,
waking and sleeping, youth and
old age, because the former
things having changed are now
the latter, and when those latter
things change, they
become the former.
- Heraclitus
(quoted in
pseudo-Plutarch,
Consolation to
Apollo )
Being is ungenerated and indestructible, whole, of
one kind and unwavering, and complete. Nor was
it, nor will it be, since now it is, all together, one,
continuous...That it came from what is not I shall
not allow you to say or think — for it is not
sayable or thinkable
that it is not...How
might what is then
perish? How might it
come into being? For
if it came into being it
is not, nor is it if it is
ever going to be. Thus
generation is
quenched and perishing unheard of.
- Parmenides
circa 480 BC
Science Is About Simplification
PHILOSOPHIÆ NATURALIS PRINCIPIA MATHEMATICA
AUCTORE ISAACO NEWTONO
Editio tertia MDCCXXVI
Axiomata sive Leges Motus
Lex I
Corpus omne perseverare in statu suo quiscendi vel movendi uniformiter in directum,
nisi quatenus a viribus impressis cogitur statum illum mutare.
Lex II
Mutationem motus proportionalem esse vi motrici impress", et fieri secundum lineam
rectam qua vis illa imprimitur.
Lex III
Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones
in se mutuo semper esse æquales et in partes contrarias dirigi.
PHILOSOPHIÆ NATURALIS PRINCIPIA MATHEMATICA
Author Isaac Newton
Third edition (1726)
Three Laws of Motion
Law I
Every object in a state of uniform motion tends to remain
in that state of motion unless an external force is applied
to it.
Law II
The relationship between an object's mass m, its
acceleration a, and the applied force F is
F = ma.
Law III
For every action there is an equal and opposite reaction.
Everything pertaining from
astronomical motion to
falling here on Earth can be
fully described by Newton’s
Law of Gravity plus his
laws of motion.
m1m2
F G 2
r
Science Is About Simplification
James Clerk Maxwell (~1864)
 
D  
 
Modern Nomenclature
B  0


J

 
 
B
E  
c o
t

   D
H  J 
t
Electricity
ElectroMagnetism
Magnetism
Light
Three
Become
one
Then may we not fairly
plead in reply that our
true lover of knowledge
naturally strives for
truth, and is not content
with common opinion,
but soars with
undimmed and unwearied
passion till he grasps
the essential nature of
things ?
- Plato
Republic
• Science addresses many things:
– What is the ultimate nature of reality?
– What is the simplest expression of nature?
– Amongst all of the undeniable change, is there
anything that is permanent and enduring?
– How did the universe come into existence and
what is its ultimate fate?
– What is the ultimate answer to the ultimate
question?
Mensans
PUNS
‫ا هلل‬
What is the root of it all?
From where comes meaning?
DOG
Dyslexic
Christians
Moslems
GOD
Christians
Beauty in the Universe
Innermost Space
High Energy Particle Physics is a
study of the smallest pieces of
matter.
It investigates the deepest and
most fundamental aspects of
nature.
It investigates (among other
things) the nature of the universe
immediately after the Big Bang.
It also explores physics at
temperatures not common for the
past 15 billion years (or so).
Helium
Periodic Table
Neon
All atoms are made
of protons, neutrons
and electrons
u u
d
Proton
u
d d
Neutron
Gluons hold quarks together
Photons hold atoms together
Electron
u
d
b
While quarks have similar
electric charge, they have
vastly different masses
(but zero size!)
s
c
t
a=e2/ħc
Fermi National Accelerator Laboratory
(a.k.a. Fermilab)
Jargon alert: 1 Giga Electron Volt
(GeV) is 100,000 times more energy
than the particle beam in your TV.
If you made a beam the hard way,
it would take 1,000,000,000 batteries
• Begun in 1968
• First beam 1972
(200, then 400 GeV)
• Upgrade 1983
(900 GeV)
• Upgrade 2001
(980 GeV)
 The Main Injector upgrade was completed in 1999.
 The new accelerator increases the number of
possible collisions per second by 10-20.
Expected
Number
of
Events
 DØ and CDF have undertaken massive
upgrades to utilize the increased
Huge statistics
collision rate.
for precision physics
at low mass scales
1000
100
Formerly rare processes
become high statistics
processes
10
Run II
1
 Run II began March 2001
Increased reach
for discovery physics
at highest masses
Run I
Increasing ‘Violence’
of Collision
How Do You Detect Collisions?
• Use one of two large multi-purpose particle
detectors at Fermilab (DØ and CDF).
• They’re designed to record collisions of
protons colliding with antiprotons at nearly
the speed of light.
• They’re basically cameras.
• They let us look back in
time.
Typical Detector (Now)
30’
• Weighs 5,000 tons
• Can inspect
10,000,000
collisions/second
• Will record 50
collisions/second
• Records
approximately
10,000,000
bytes/second
• Will record 1015
(1,000,000,000,000,000)
50’
bytes in the next
run (1 PetaByte).
Spooky?
Remarkable Photos
In this collision, a top and
anti-top quark were created,
helping establish their existence
This collision is the most violent
ever recorded (and fully
understood). It required that
particles hit within 10-19 m or
1/10,000 the size of a proton
Modern Cosmology
• Approximately 15 billion
years ago, all of the matter in
the universe was concentrated
at a single point
• A cataclysmic explosion (of
biblical proportions perhaps?)
called the Big Bang
caused the matter to fly apart.
• In the intervening years, the universe has been expanding,
cooling as it goes.
Big Bang Theory
White Sox
Version
• A black body radiator is one
which absorbs all light which is
incident on it.
• Such a body can also emit light,
if sufficiently hot.
• Since the universe is the remnant
of a hot explosion, it should thus
have a temperature and an
‘afterglow’.
Black Body Radiator
Universe
Afterglow From the Big Bang
Afterglow From the Big Bang
• In 1964, while working at Bell Labs, Penzias and Wilson discovered a radio
hiss that they couldn’t make go away.
• They had (by accident!) discovered the remnant ‘echo’ of the Big
• The universe was shown to have a temperature of 2.726K (-450 °F)
Bang
How Does the Afterglow Work?

+

+


+

+
+
+


+

+
+

+
Proton

Electron
Photon
How Does the Afterglow Work?
H
H
H
H
H
H
H
H
H
H
H
H
H
H
+
Proton
+

= H
Electron Hydrogen
+
Proton

Electron
Photon
Mysteries of the Afterglow
The temperature of the universe is uniform everywhere to parts per
million.
Why?
The temperature of the universe has slight non-uniformities, at the
parts per million.
Why?
Answers to both of these questions
exist but are beyond the scope of
this talk. Get Peter to bring in
a cosmologist soon.
History of the Universe (Readers Digest Version)
the universe was all concentrated
You are here
at a single spot
Then God (or whoever, I’m not
getting into that tonight) said “Let there be light,”
and instead there was a vast explosion that created the
universe and spread all of the matter that has ever been
observed (and more) throughout the Cosmos.
Hmmmmmmmmmm…..
Large explosions  hot temperatures  very high
energies
Ice melts  water evaporates  steam ionizes  atomic
nuclei break apart  quarks escape the nuclei….
Now
(13.7 billion years)
Stars form
(1 billion years)
Atoms form
(380,000 years)
Nuclei form
(180 seconds)
Nucleons form
(10-10 seconds)
Quarks differentiate
(10-34 seconds?)
??? (Before that)
4x10-12
seconds
The Universe’s Recipe
Mysteries
How do we know about the
universe before 10-12 seconds?
Just what is the simplest and most
fundamental thing in the universe?
Does the unification/simplification
stuff discussed earlier continue to
hold?
• The forces have been
unified. What about
the particles?
The Early Universe
Possibly the true nature of particles
is that they are actually minute
vibrating 11-dimensional strings.
Freebie: This theory is the only
candidate way to unify gravity with
the quantum forces.
Standard Model Summary
The Standard Model (quarks, leptons, three generations and four
currently-distinct forces)
Can explain all known experimental data, from:
The birth of the universe (10-12 seconds) to now.
Motionless objects, to those traveling at the speed of light.
Temperatures from absolute zero to the Big Bang.
Lotsa stuff…..
Cannot explain
The very early universe (before 10-12 seconds).
Do the forces unify?
Are there many particles or just strings?
Lotsa stuff…..
Data-Model Comparison
Data-Model Comparison
It is not possible to be
ignorant of the end of things
if we know their beginning.
-Thomas Aquinas
Summa Theologica
www-d0.fnal.gov/~lucifer/PowerPoint/PopTalk_Jan2005.ppt
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