PHIL 160: Lecture 2PHIL 160: Lecture 2

I.I. Science news…Science news…II.II. Some background on the Tevatron and the Some background on the Tevatron and the

(never-built) Superconducting Super Collider(never-built) Superconducting Super ColliderIII.III. Three of Lederman’s analogies and what they Three of Lederman’s analogies and what they

suggest about contemporary particle physics suggest about contemporary particle physics (and other fields pursuing the “most basic (and other fields pursuing the “most basic stuff” of the universe and an answer to “how stuff” of the universe and an answer to “how does the universe work?”)does the universe work?”)

IV.IV. Preview of Gould reading.Preview of Gould reading.

FermilabFermilab

Welcome to Fermilab!Welcome to Fermilab!

Our mission is to discover what the universe is Our mission is to discover what the universe is made of and how it works.made of and how it works.

We're asking three simple, challenging questions We're asking three simple, challenging questions here at the frontier of particle physics:here at the frontier of particle physics:

What is the nature of the universe?What is the nature of the universe?

What are matter, energy, space and time?What are matter, energy, space and time?

How did we get here and where are we going?How did we get here and where are we going?

Fermilab Director Michael S. WitherellFermilab Director Michael S. Witherell

The Standard ModelThe Standard Model

FermilabFermilab

The TevatronThe Tevatron

Was the world’s highest-energy Was the world’s highest-energy particle colliderparticle collider

4 miles in circumference and 4 miles in circumference and housed in a tunnel 30 feet housed in a tunnel 30 feet below the ringbelow the ring

Accelerators send particles racing Accelerators send particles racing around the Tevatron at around the Tevatron at 99.9999% of the speed of light99.9999% of the speed of light

Smashing particlesSmashing particles

Send two kinds of subatomic particles, protons Send two kinds of subatomic particles, protons and antiprotons, around the ring in opposite and antiprotons, around the ring in opposite directions.directions.

At two points, beams of these particles flow right At two points, beams of these particles flow right into each other.into each other.

Causing Causing millions and millions of collisionsmillions and millions of collisions, at the , at the rate of almost two million each second. rate of almost two million each second.

Many kinds of devicesMany kinds of devices record details of the debris record details of the debris to identify, to identify, based on theorybased on theory, what kinds of , what kinds of particleparticle are being produced in the collisions. are being produced in the collisions.

Smashing particlesSmashing particles

Using the Tevatron, Fermilab Using the Tevatron, Fermilab scientists have confirmed:scientists have confirmed:

The bottom quark (1977)The bottom quark (1977)

The top quark (1995)The top quark (1995)

The tau neutrino (2000)The tau neutrino (2000)

““We collide particles in the We collide particles in the hope of seeing something hope of seeing something never seen before.”never seen before.”

But But predictedpredicted by theory! by theory!

The detectorsThe detectors

The CDF Collider Detector.The CDF Collider Detector.

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

Part IIPart II

Lederman’s analogiesLederman’s analogies

The “library of matter”What are What are the most basic the most basic

elementselements of a library? of a library?

Books? No, they are Books? No, they are complexcomplex

Words? No, they are also Words? No, they are also complexcomplex

Letters? No, can be broken Letters? No, can be broken down into just 0 and 1…down into just 0 and 1…

If it makes no sense to take If it makes no sense to take apart the 0 and the 1, apart the 0 and the 1, we’ve found the “atomic” we’ve found the “atomic” components of the librarycomponents of the library

The universe as the libraryThe universe as the library

What are What are its most basic its most basic elements?elements?

The The forces of natureforces of nature are the are the grammar, spelling, and grammar, spelling, and algorithmalgorithm

The The subatomic particles, subatomic particles, quarks and leptonsquarks and leptons, are , are currently believed to be the currently believed to be the “atomic” (un-cut-able) “atomic” (un-cut-able) elements of the universe elements of the universe

The “pyramid of science”The “pyramid of science”

Dependent uponDependent upon

..

..

..

BiologyBiology

ChemistryChemistry

PhysicsPhysics

CausalCausal

MathematicsMathematics

Lederman’s analogiesWhat basic assumptions can we identify that underlie and What basic assumptions can we identify that underlie and

motivate research in particle physics?motivate research in particle physics?

That the entities and laws studied by particle physicists are That the entities and laws studied by particle physicists are what make up and govern all other entities and what make up and govern all other entities and processes and regularities.processes and regularities.

A commitment to simplicity (just a few particles and a few A commitment to simplicity (just a few particles and a few laws): nature is (ultimately simple – i.e., elegant)laws): nature is (ultimately simple – i.e., elegant)

That “invisible” (not able to be directly observed) objects are That “invisible” (not able to be directly observed) objects are respectable – and, indeed, necessary for (some) theories respectable – and, indeed, necessary for (some) theories of physics.of physics.

What warrants these assumptions?What warrants these assumptions?

Invisible soccer balls and evidence for objects or processes that cannot be directly observed

Evidence is at times indirect and Evidence is at times indirect and involves drawing inferencesinvolves drawing inferences

Positing the existence of a ball Positing the existence of a ball that they that they could not observecould not observe, the , the Twiloins were able to Twiloins were able to make make sense of what they could sense of what they could observeobserve..

Scientists often posit an object Scientists often posit an object (or force or process) that cannot (or force or process) that cannot be directly observed when its be directly observed when its existence existence makes sense makes sense of/explainsof/explains what what cancan be be observed.observed.

Invisible soccer ballsInvisible soccer balls

Previously unobservablePreviously unobservable

entities posited by science:entities posited by science: MoleculesMolecules GenesGenes AtomsAtoms DNADNA Early stages of the universeEarly stages of the universe Hominid ancestorsHominid ancestors ExtinctionsExtinctions

What is Lederman’s evidence?What is Lederman’s evidence?

““My evidence for atoms and quarks is as good as the My evidence for atoms and quarks is as good as the evidence [the TV provides that the Pope exists].evidence [the TV provides that the Pope exists].

““What is that evidence? Tracks of particles in a What is that evidence? Tracks of particles in a bubble chamber. In the Fermilab accelerator, the bubble chamber. In the Fermilab accelerator, the “debris” from a collision between a proton and an “debris” from a collision between a proton and an antiproton is captured by a 3 story, 60 million antiproton is captured by a 3 story, 60 million dollar detector. …dollar detector. …

““Here, the “evidence” – the “seeing” – is tens of Here, the “evidence” – the “seeing” – is tens of thousands of sensors that develop an electrical thousands of sensors that develop an electrical impulse when a particle passes…”impulse when a particle passes…”

What is Lederman’s evidence?What is Lederman’s evidence?

““All of these impulses are fed by through hundreds All of these impulses are fed by through hundreds of thousands of wires to electronic data processors.of thousands of wires to electronic data processors.

““Ultimately, a record is made on spools of magnetic Ultimately, a record is made on spools of magnetic tape, encoded by zeroes and ones.tape, encoded by zeroes and ones.

““Science, especially particle physics, gains Science, especially particle physics, gains confidence in its conclusions by duplication” and confidence in its conclusions by duplication” and by frequent tests of the experimental apparatus.by frequent tests of the experimental apparatus.

What commitments does Lederman embrace What commitments does Lederman embrace (or, what assumptions does he make)?(or, what assumptions does he make)?

Ontological: concerning what there is…Ontological: concerning what there is…

Epistemological: concerning the possibility, limits, Epistemological: concerning the possibility, limits, and strengths of our abilities to know…and strengths of our abilities to know…

Theoretical-technologyTheoretical-technology

Aesthetic: concerning what we find beautiful or Aesthetic: concerning what we find beautiful or pleasingpleasing

Evolutionary theorizingEvolutionary theorizing

The late great Stephen Jay The late great Stephen Jay GouldGould

(1941-2002)(1941-2002)Harvard paleontologist and Harvard paleontologist and

evolutionary theoristevolutionary theoristOne of the strongest defenders One of the strongest defenders

of Darwin and evolutionary of Darwin and evolutionary theorytheory

One of the strongest critics of One of the strongest critics of some aspects of some aspects of evolutionary theory.evolutionary theory.

Natural selectionNatural selection

Darwin’s “great discovery”Darwin’s “great discovery” A A mechanism by which evolution could occurmechanism by which evolution could occur..

What it is…What it is… 1. There is intra-species variation.1. There is intra-species variation. 2. There is a struggle for existence.2. There is a struggle for existence. 3. If some variation provides an advantage (however 3. If some variation provides an advantage (however

small…) in terms of survival and/or reproductive small…) in terms of survival and/or reproductive success, those organisms with it will success, those organisms with it will tendtend toto survive survive better and reproduce more successfully better and reproduce more successfully and tendand tend toto pass on the trait to their offspring. pass on the trait to their offspring.

Natural selectionNatural selection

Darwin’s “great discovery”Darwin’s “great discovery” A A mechanism by which evolution could occurmechanism by which evolution could occur..

Gould’s main argument (the panda’ “thumb” and Gould’s main argument (the panda’ “thumb” and “contrivances” of orchids are used as evidence “contrivances” of orchids are used as evidence and illustrations): it is imperfections that and illustrations): it is imperfections that constitute the strongest evidence for evolution.constitute the strongest evidence for evolution.

What does he mean by ‘imperfections’? And why What does he mean by ‘imperfections’? And why does he regard them as so significant?does he regard them as so significant?

What is it about pandas and about orchids that is What is it about pandas and about orchids that is taken to be evidence of “imperfect ‘design’”?taken to be evidence of “imperfect ‘design’”?