Download Why Philosophy of Physics is Awesome!

Why Philosophy of Physics is
Awesome!
Niels Martens
DPhil Candidate Philosophy of Physics
Oxford University
Epistemology
Metaphysics
Philosophy of Science
(Anti)-realism
Phil of Mathematics
Gravity, Space, Time
& Space-time
Specific
sciences
Specific sciences
Scientific method
Phil of Biology
Phil of Mind
Quantum (info)
Phil of Physics
Phil of Physics
Thermodynamics/
Statistical Mechanics
Philosophy @ Oxford
 Philosophy, Politics & Economics
 Philosophy & Theology
 Psychology, Philosophy & Linguistics
 Philosophy & Modern Languages
 Classics
 Mathematics & Philosophy
 Computer Science & Philosophy
 Physics & Philosophy
Oxford Philosophers of Physics
Philosophy of Space
Philosophy of Space
 Is space real?
 Einstein’s Relativity Theory
 Time slows down!
 Space contracts!
 Cosmology/Big Bang
 Emergent Space(time)
Leibniz-Clarke Correspondence
Newton
Clarke
SUBSTANTIVALISM
 Space exists!
 It makes sense to talk
about empty space
 ‘Even if there is no
play tonight, the
theatre is still there’
Leibniz
RELATIONALISM
 All talk about space is
reducible to talk about
relations between particles
 Compare with family
relations
“Leibniz shifts”: space must be relational
 Principle of Sufficient Reason
Immanuel Kant: Let’s use your left and
right hands
 There is a difference between your right and left hand
 The relationalist explains the different handedness of two
objects via relations
 What about a single hand in an empty universe?
“Newton’s bucket”: let’s look at science!
Ernst Mach
 The relative motion between
bucket and water is the same in
picture 1 and 3, but the relative
motion with respect to the stars is
not!
 Problem: physics becomes
nonlocal
Philosophy of Quantum Mechanics
Philosophy of Quantum Mechanics
 Metaphysics: What does the world look like according to
quantum mechanics?
 Quantum information
 Probability/determinism/free will
Interpreting Quantum Mechanics
 Does light (and everything else in the world) consist of
particles? Or waves?
 Photo-electric effect (Einstein  Nobel Price): particles
 Double split experiment: waves
Double slit experiment
Double slit experiment
Double slit experiment
Double slit experiment
Double slit experiment
 Does each photon (light particle) go through both slits at the
same time? Can we measure which slit it goes through?
 Even if you only send one photon through the slits, we still
get a (probabilistic) interference pattern!
  Photons are waves (and electrons, and protons, and all
other matter)
 You cannot say that there is a localised particle that goes
through one of the two slits: there is a wave that goes through
both slits: the photon is in a SUPERPOSITION of going
through the left and the right slit at the same time
This is absurd!
 So, at the smallest scale, our world consists of quantum
waves: light, electrons, protons, everything is a quantum
wave, meaning that the `particles’ are at several places at the
same time.
Schrödinger (Magdalen College Alumnus):
This cannot be true.
If it would be true, it should also apply to large objects
(since they are made up out of small objects), and it would be
absurd to have a large object - like a table - being here and
somewhere else at the same time!
We never see tables in superpositions!
Schrödinger’s cat
Ways out
 Instrumentalism (or the shut-up-and-calculate school)
 Measurement `collapses the wavefunction’
 If you measure with a big apparatus, you will find the particle or
cat in one specific location/state: the probability of that
location/state depends on how big the wave is at that point.
 Consciousness `collapses the wavefunction’
 Pilot-wave theory
 Many-worlds interpretation
Questions?