PHIL 160: Lecture 2

1. PHIL 160: Lecture 2 • Science news… • Some background on the Tevatron and the (never-built) Superconducting Super Collider • Three of Lederman’s analogies and what they suggest about contemporary particle physics (and other fields pursuing the “most basic stuff” of the universe and an answer to “how does the universe work?”) • Preview of Gould reading.

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 physics:What 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 Standard Model

4. Fermilab The Tevatron Was the world’s 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

5. Smashing particles Send two kinds of subatomic particles, protons and antiprotons, around the ring in opposite directions. At two points, beams of these particles flow right into each other. Causing millions and millions of collisions, at the rate of almost two million each second. Many kinds of devices record details of the debris to identify, based on theory, what kinds of particle are being produced in the collisions.

6. Smashing particles Using the Tevatron, Fermilab scientists have confirmed: The bottom quark (1977) The top quark (1995) The tau neutrino (2000) “We collide particles in the hope of seeing something never seen before.” But predicted by theory!

7. The detectors The CDF Collider Detector. 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.

8. Part II Lederman’s analogies

9. What are the most basic elements of a library? Books? No, they are complex Words? No, they are also complex Letters? No, can be broken down into just 0 and 1… If it makes no sense to take apart the 0 and the 1, we’ve found the “atomic” components of the library The universe as the library What are its most basic elements? The forces of nature are the grammar, spelling, and algorithm The subatomic particles, quarks and leptons, are currently believed to be the “atomic” (un-cut-able) elements of the universe The “library of matter”

10. The “pyramid of science” Dependent upon . . . Biology Chemistry Physics Causal Mathematics

11. Lederman’s analogies What basic assumptions can we identify that underlie and motivate research in particle physics? That the entities and laws studied by particle physicists are what make up and govern all other entities and processes and regularities. A commitment to simplicity (just a few particles and a few laws): nature is (ultimately simple – i.e., elegant) That “invisible” (not able to be directly observed) objects are respectable – and, indeed, necessary for (some) theories of physics. What warrants these assumptions?

12. Invisible soccer balls and evidence for objects or processes that cannot be directly observed • Evidence is at times indirect and involves drawing inferences • Positing the existence of a ball that they could not observe, the Twiloins were able to make sense of what they could observe. • Scientists often posit an object (or force or process) that cannot be directly observed when its existence makes sense of/explains what can be observed.

13. Invisible soccer balls • Previously unobservable entities posited by science: • Molecules • Genes • Atoms • DNA • Early stages of the universe • Hominid ancestors • Extinctions

14. What is Lederman’s evidence? “My evidence for atoms and quarks is as good as the evidence [the TV provides that the Pope exists]. “What is that evidence? Tracks of particles in a bubble chamber. In the Fermilab accelerator, the “debris” from a collision between a proton and an antiproton is captured by a 3 story, 60 million dollar detector. … “Here, the “evidence” – the “seeing” – is tens of thousands of sensors that develop an electrical impulse when a particle passes…”

15. What is Lederman’s evidence? “All of these impulses are fed by through hundreds of thousands of wires to electronic data processors. “Ultimately, a record is made on spools of magnetic tape, encoded by zeroes and ones. “Science, especially particle physics, gains confidence in its conclusions by duplication” and by frequent tests of the experimental apparatus.

16. What commitments does Lederman embrace (or, what assumptions does he make)? • Ontological: concerning what there is… • Epistemological: concerning the possibility, limits, and strengths of our abilities to know… • Theoretical-technology • Aesthetic: concerning what we find beautiful or pleasing

17. Evolutionary theorizing The late great Stephen Jay Gould (1941-2002) Harvard paleontologist and evolutionary theorist One of the strongest defenders of Darwin and evolutionary theory One of the strongest critics of some aspects of evolutionary theory.

18. Natural selection • Darwin’s “great discovery” • A mechanism by which evolution could occur. • What it is… • 1. There is intra-species variation. • 2. There is a struggle for existence. • 3. If some variation provides an advantage (however small…) in terms of survival and/or reproductive success, those organisms with it will tendto survive better and reproduce more successfully and tendto pass on the trait to their offspring.

19. Natural selection • Darwin’s “great discovery” • A mechanism by which evolution could occur. • Gould’s main argument (the panda’ “thumb” and “contrivances” of orchids are used as evidence and illustrations): it is imperfections that constitute the strongest evidence for evolution. • What does he mean by ‘imperfections’? And why does he regard them as so significant? • What is it about pandas and about orchids that is taken to be evidence of “imperfect ‘design’”?