Department

History and Philosophy of Science and TechnologyCourse Code

HPS211H1Professor

Curtis ForbesThis

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Stern Gerlach Experiment

Electron being represented by wave function in nature

two distinct probability functions

superposition of states

cannot find electron

Schrodinger's Cat

How far can we take superposition

box with cat and radioactive material- probability that it will decay is 1/2

when it finishes enables hammer to hit a gong which releases gas and kills cat

how do we know if cat is dead or live

some ppl claim it is in a superposition of state- one half dead, one half alive

but schrodinger claims it is ridiculous to apply quantum mechanics (with superposition of states

and indeterminism) to macro world (determinism)

no scientific theory that est at what scale you have quantum and what is macro

Einstein

formulated rules of general and special relativity

special relativity claims nothing can go faster than the speed of light

Einstein-Podolsky-Rosen Paradox: two observers; we have a neutron- which has slight

probability of decaying into proton- electron; the particle that is made from it must also be

neutral; after the decay can be both arrows up or both arrows down (spin); before one side

measures the proton it is in superposition of both states up and down but the moment he

measured it was up (from his side); moment you measure it changes state of ; the lines between

quantum and macro actually exists;

quantum field theory makes quantum mechanics relativistic by removing all observables-spin,

etc.

clear contradiction between our understanding of determinism and finiteness of nature that is

being challenged

A Quantum Mechanical Worldview

it is an approximate theory but never been proven wrong

What was the quantum revolution?

The dawn of the 20th century saw a buildup of experimental anomalies- disproved wave theory

and particle theory of light

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