Transcript ppt file - Fermi Society of Philosophy

Schrodinger’s Cat is dead OR alive
NOT a superposition
NOT to do with observation,measurement or consciousness
Mike Albrow – Fermi Philo Soc June 8th 2014
Thinking and consciousness are not 1-dimensional, and not EITHER-O
Consider a single neutron at rest ( = in its rest frame)
In absence of magnetic field, exactly one state N, & microscopic entropy
S = k. ln W = 0
W = # possible microscopic states consistent with the macroscopic state.
After some time, random with an exponential decay probability τ = 14.76 min
n p e ν
3 x 3 momentum components – 4 E,p conservation constraints  5 dim phase space
Very large number W of possible final states & S
= k. ln W jumps.
There is no going back, although A( p + e + ν  n) is same (T-invariance)
Entropy only increases (except perhaps in a BIG CRUNCH).
p
n
ν
e
The p, e, and ν proceed as waves
Obeying wave equations until an
Interaction = S-jump occurs.
Every interaction (ionization e.g.)
Is an S-jump and a ψ-collapse
Fermilab 15’ Neon Bubble Chamber: neutrino-nucleus collision
An atom is 1 million
times smaller than
this bubble.
Atom  electron + ion
“amplification”
4
UA1 Drift Chamber
Every point is a measurement on a wire.
Ionized atom  avalanche  amplification  signal  recording
High energy electron from W decay
WIRE at HV
Cascade of electron-ion pairs
Each “event” S-jumps and ψ-collapses
GAS in Drift Chamber
Radioactive source e.g. a neutron (15 minute half-life)
In one half-life
0.5
0.5
Geiger counter
Triggers a switch
Breaks a vial of arsenic
At every stage, ENTROPY S JUMPS
S = k ln W
W = # possible states
[ i.e phase space]
Releases poison into box
Kills the cat
Entropy is not local, defined for a system
Wave function is not local either
Obeying all conservation laws
In their space-time domain
Accounting for Heisenberg U.P.
ΔE. Δt >= ħ
Δp.Δx >= ħ
The basic issue: Wave-function collapse
Common theorists response: “Don’t talk to me about wave-function collapse.”
“Shut up and calculate!”
They have the procedures to calculate Feynman diagrams, g-2 etc. without “understanding”
Feynman said: No-one really understands quantum mechanics.
I don’t claim to. Simply replace “conscious observation, measurement”  entropy-jump.
And accept that wave-function collapse is spacelike without violating SR.
Quantum Mechanics deals with wave-functions ψ(x,t)
and also with particles, e.g. electron e.
The wave function evolves in accordance with deterministic dynamical laws,
it will spread out from a source and be non-local.
At any point in space x and time t the probability of finding an electron, Pe(x,t)
is given by the product Pe(x,t) = ψe*(x,t) ψe(x,t)
as ψ(x,t) has real and imaginary parts, and ψ*(x,t) is the complex conjugate,
Well-known, simple, and magic: Young’s slits
Plane monochromatic light wave incident on a pair of slits.
Diffraction pattern builds up on screen, very different from
pattern with only one slit open. Classic wave phenomenon.
Make detector sensitive to single photons (we have them now!).
Weaken light source so only one photon detected / second.
Same pattern builds up. Photon wave-function must go through
(or “know about”) both slits.
Even more amazing: Do same experiment with an electron beam!
Identical behavior.
Electron has one unit of electric charge, it cannot be split.
The electron wave-function ψe(x,t)
went through both slits, but the electron
was detected (I did not say observed)
at one space point.
The e-wave was spread out (non-local)
but the electron particle was localised.
When that transition happened
ψe(x,t)  0 elsewhere. Very quickly!
Wave-function collapse
You know the answer! Al least I think you do.
Consciousness, measurements and observers can have nothing to do with
wavefunction collapse.
Another try:
There are two sorts of physical systems in the world:
A: Purely microscopic systems
as long as they remain isolated from outside influences, always evolve in accordance
with the dynamical equations of motion.
B: Macroscopic systems (which contain microscopic subsystems) evolve but it can happen
that two different macroscopic conditions get superimposed (two slit paths) and then
the whole system collapses.
Problems: No absolute distinction between microscopic and macroscopic.
There is a continuum. Molecules can be as simple as H2 or big, fullerenes even DNA,
and macroscopic crystals ...
YES! 1 μm fringes
I agree Quantum mechanics is weird, but it is not preposterous
I am not claiming to solve the weirdness,
but want to lay to rest the preposterous idea that things like cats can be in some
“mixed state” until “observed” or “measured” by a conscious being.
Schrodinger himself used the cat story to show the absurdity of a wave-function
evolving to such complexity before “collapsing”.
My approach is “realistic”
We now know:
The Universe evolved from a compact (~ Planck length?) Big/small Bang/whisper
>>> No life until at least after the first supernovae ejected carbon & other heavy elements
>>> After some 109 years life began somewhere (surely many places) and eventually
evolved, at least on Earth, into thinking, observing, measuring beings like us.
>>> There is no definable dividing line between non-thinking and thinking
“
“
“
“
between non-conscious and conscious.
These are continua, and also not 1-dimensional
High energy collisions, bubble chambers, drift chambers, whatever….
Maybe 100 million collisions/second, recorded electronically
(with film in bubble chamber days) to tapes or mass storage devices
Read by programs and entries made in histograms.
E.g. Higgs H(126)
γγ was only ever “observed” as a bump in a mass plot.
Nobody (surely?) believes that the events did not really occur months beforehand.
But particle collisions are described by quantum mechanical wave-functions.
Feynman diagrams are a neat way of calculating Q-Mech processes.
Simple 2  2 processes described by scattering amplitudes S(s,t,u)
of the (complex) wave functions ψ(x,t)
… and then particles come out.
From David Albert, Quantum Mechanics and Experience (1992):
John von Neumann, Mathematical Foundations of QM (1955):
Two fundamental laws about how states of QM evolve:
I) When no measurements are going on, the states of all physical systems invariably evolve
in accordance with the dynamical equations of motion.
II) When there are measurements going on, the states of the measured systems evolve in
accordance with the postulate of collapse, not in accordance with the dynamical equations
of motion.
NO GOOD! What do you mean by “measurements going on” ?
What constitutes a measurement? Does in need an “observer” ?
Who or what is an observer?
Does it need a conscious or sentient observer?
Sentience is the ability to feel, perceive, or to experience subjectivity.
Is a worm sentient?
Is consciousness a YES/NO thing, that during our long evolution creatures that were not
conscious suddenly became conscious creatures?