The strange world of contemporary physics

1
The strange world of contemporary physics

Slide 1 (of 28                                   
                                                  
                                           
2
Fermilab

• Welcome to Fermilab!
• Our mission is to discover what the universe is
  made of and how it works.We're asking three
  simple, challenging questions here at the
  frontier of particle physicsWhat is the nature
  of the universe?What are matter, energy, space
  and time?How did we get here and where are we
  going?Fermilab Director Michael S. Witherell

3
The ancient Greeks

• What is everything made of and how does the
  answer to this question explain change?
• Contemporary version What is everything made of?
  And assuming they are fundamental, what are
  matter, energy, space and time?
• The one and many
• Appearance and reality

4
The Standard Model
5
Fermilab

• The Tevatron
• Worlds highest-energy particle collider
• 4 miles in circumference and housed in a tunnel
  30 feet below the ring
• Accelerators send particles racing around the
  Tevatron at 99.9999 of the speed of light so
  that the particles complete the four mile course
  nearly 50,000 times a second

6
Smashing particles

• Methods
• Take speeding subatomic particles
• and smash them together at high
• energies.
• Send two kinds of particles,
• protons and antiprotons, around the
• ring in opposite directions.
• At two points in the ring, streams of these
  particles (called "beams") flow right into each
  other
• What follows are millions and millions of
  collisions, at the rate of almost two million
  each second.
• Computer View of Proton-Antiproton Collision

7
Smashing particles

• Using the Tevatron, Fermilab scientists have
  discovered
• The bottom quark (1977)
• The top quark (1995)
• The tau neutrino (2000)
• We collide particles in the hope of seeing
  something never seen before

8
Detecting particles

• Collider detectors about the size of small
  apartment buildings are used to see these
  particles.
• Fermilab's two collider detectors are about four
  stories high and weigh some 5,000 tons (10
  million pounds) each.
• The particle collisions occur in the center of
  the detectors, which are crammed with electronic
  instrumentation. DZero Collider Detector

9
The detectors

• Each detector has about one million individual
  pathways for recording electronic data generated
  by the particle collisions. The signals are
  carried over nearly a thousand miles of wires and
  cables--each one connected by hand and tested
  individually.
• CDF Collider Detector.

10
The detectors

• It takes lots of patience to work on a particle
  physics experiment.

11
Invisible soccer balls (or the Pope) and evidence

• Evidence is at times indirect and inferential
• Scientists often posit an object (or force or
  process) that cannot be observed but the
  existence of which would make sense of/explain
  what can be observed (might include individual
  objects and/or events, and/or include generalities

12
What ontological, epistemological, and
methodological commitments does Lederman embrace?

• Ontological what does the metaphor of a library
  of matter suggest?
• Epistemological what does Ledermans discussion
  overall suggest about the possibility and nature
  of knowledge about subatomic particles? And what
  does it suggest about the importance of such
  knowledge?
• Ontological/Epistemological/Methodological What
  does Ledermans example involving an invisible
  soccer ball indicate about his commitments and
  how they are related?

13
Profound Insights of the Laureates by Marc
Abrahams Lederman and I spoke at a conference at
Woods Hole. Q. When you put on your pants, which
leg do you put on first? A. Left. Q. What color
socks are you wearing, and why? A. Brown. My wife
packed them. Q. How many pair of socks do you
recommend a person should own? A. Twenty. Most of
them should be matching. Q. Do you have any
advice for young people who are entering the
field? A. Yes.