1. How
We
See
the
Ma,er
That
Makes
All
Things
Steven
Spencer
Applied
Mathema;cian
Philosophers
Corner
2nd
October
2012
1

2. Outline
• The
world
of
classical
physics
• Things
don’t
quite
add
up!
• Enter
the
quantum
• The
mechanics
and
the
quantum
• Stranger
and
stranger
• What
does
it
mean?
• Where
is
the
mind
in
all
this?
• Are
you
sure?
2

3. The
world
of
classical
physics
• Determinis,c
(Laplace
1749
-­‐
1827)
• External
observer
and
isolated
experimental
systems
• Par,cles
(Newton
1642
-­‐1727)
• Waves
(Hooke,
Huygens,
Young,
Maxwell)
3
• Atomic
theory
(Dalton)

4. Things
don’t
quite
add
up
• Black-­‐body
thermal
radia,on
→
colours
• Stable
atoms
• Line
emission
spectra
• Photoelectric
effect
4

5. Enter
the
Quantum
• The
physics
of
atomic
and
sub-­‐atomic
scales?
• Energy
is
emiUed
in
‘bits’
(quanta)
(Planck,
1900)
→
tricky
maths?
•
Energy
in
light
is
in
‘grainy
bits’
(photons)
which
are
par$cles
with
wave
proper,es
→
photoelectric
effect
(Einstein,
1905)
5

6. Two
views
of
EM
radia;on
• Light
is
a
wave!
Light
is
a
par,cle!
6

7. The
Mechanics
and
the
Quantum
• Orbital
atomic
theory
(Rutherford,
1911)
• Quan,sed
electron
orbit
atomic
model
(Bohr,
1913)
→
‘flights
and
perchings’
• Par,cles
are
waves!
(de
Broglie,
1924)
→
orbi,ng
electrons
have
integer
wavelengths!
• Matrix
mechanics
(Heisenberg,
1925)
→
unanschaulich
atomic
world!
7

8. • Wave
mechanics
(Schrodinger,
1926)
→
how
the
quantum
state
of
a
system
evolves
with
,me.
Anschaulich
atomic
world?
• Complementarity
–
wave-­‐par,cle
duality
• Determinis$c
descrip,on
for
wave
func$ons
+
Sta$s$cal
descrip,on
of
maUer
and
energy.
• Uncertainty
principle
(Heisenberg,
1927)
Momentum
and
posi$on
cannot
be
simultaneously
measured
with
unlimited
precision.
8

9. The
observer
and
the
system
• The
role
of
the
classical
observer
(measurement)
of
a
quantum
system
becomes
central
and
hotly
contested
–
“We
are
not
only
observers.
We
are
par,cipators.
In
some
strange
sense,
this
is
a
par,cipatory
universe.”
–
John
A.
Wheeler
9

10. The
Quantum
World?
• Wave
func,on
evolu,on
U(objec,ve
&
determinis,c)
+
measurement
R(subjec,ve)
=
confusion?!?
10

11. Electron
Double
Slit
Experiment
(Feynman)
• Detector
‘D’
turned
on
or
off
by
observer
→
affects
paUern
on
screen
by
double
slit.
Observer
affects
outcome
of
experiment!
11

12. Stranger
and
stranger
• Superposi;on
of
states
→
possible
in
quantum
but
not
classical
world
(Schrodinger’s
cat).
• Quantum
emtanglement
→
Many
par,cle
systems
have
a
complicated
combined
wavefunc,on
even
at
‘large’
distances!
• Einstein-­‐Podolski-­‐Rosen
(EPR)
effect
–
QM
is
either
‘non-­‐local’
(faster
than
light
influences)
or
is
not
a
complete
theory!
• Bell
inequali,es
–
QM
wins
again!
12

13. Schrodinger’s
Cat
Thought
Experiment!
• Quantum
superposi,on
affects
the
classical
world?
13

14. ‘Spooky
ac;on
at
a
distance’
(Einstein)
• Before
detec,on
the
electron
wave
is
‘everywhere’,
at
detec,on
the
wave
func,on
collapses
throughout
the
universe!
14

15. • Single
source
of
two
photons
–
‘spin’
observa,on
method
at
one
end
affects
observa,on
at
a
distant
point!
Do
par,cles
communicate
with
one
another
or
are
they
one
en,ty
?!?
15

16. • Standard
QM
violates
Bell’s
theorem.
Separated
par,cles
are
connected
(entanglement)!?!
• Result
confirmed
by
experiment
(Aspect,
1982)!!
16

17. What
does
it
mean?
• Star;ng
point
–
no
experiment
has
ever
been
found
that
concludes
against
QM
maths!
• Whatever
happened
to
determinism?
“God
does
not
play
dice”
–
A.
Einstein
vs
“A
physical
object
has
an
ontologically
undetermined
component
that
is
not
due
to
the
epistemological
limita,ons
of
physicists’
understanding”
–
A.
Eddington
17

18. • Ontologies
(interpreta;ons)
–
a)
Copenhagen
(Bohr,
Heisenberg
and
Born,
1927)
–
Complementarity
+
uncertainty
principle
+
measurement
+
correspondence
principle.
QM
describes
knowledge
NOT
reality!
“There
is
no
quantum
world.
There
is
only
an
abstract
physical
descrip,on.”
-­‐
N.
Bohr
“The
idea
of
intermediate
kinds
of
reality
was
just
the
price
one
had
to
pay”
–
W.
Heisenberg
18

19. b)
Many-­‐worlds
/
rela;ve
state
(EvereU,
1957)
–
universal
wavefunc,on
never
collapses
→
mul,verse
c)
Environmental
decoherence
–
rapid
disappearance
of
quantum
superposi,ons
by
interac,on
with
environment
(useful
for
many
interpreta,ons).
d)
Ensemble
(Einstein)
–
Minimalist,
sta,s,cal
–
wavefunc,on
for
large
numbers
of
par$cles
only.
e)
Rela;onal
–
different
observers
see
different
quantum
states.
19

20.
f)
Pilot-­‐wave
(de
Broglie,
Bohm)
–
Par,cles
guided
by
wavefunc,on.
Non-­‐local,
holis,c
universe,
hidden
variables.
g)
Objec;ve
collapse
(Penrose)
–
physical
mechanism
of
collapse
–
extended
QM.
h)
Conciousness
collapse
-­‐
subjec,ve
reduc,on
(von
Neumann/Wigner)
&
par,cipatory
anthropic
principle
(J.A.
Wheeler)
g)
New
theories
(many!)
–
objec,ve
R
wave
func,on
collapse
/
non-­‐linear
U
func,on.
20

21. Where
is
the
mind
in
all
this?
• What
is
a
brain?
• Dense
network
–
more
than
104
cell
bodies
and
km
of
wiring
per
cubic
mm!
• Mul,ple
cell
types:
spiking
Q: Is the mind
neurons
(1011
cells)
for
info
(consciousness)
processing,
analog
neurons
highly organised
&
‘supporter’
cells
.
brain activity?
21

22. Neuronal
Behaviour
⇒
22

23. Quantum
Theory
of
Mind
• Non-­‐algorithmic
thought
→
cannot
be
modelled
by
a
digital
(Turing)
computer.
• Consciousness
as
a
quantum
mechanical
phenomenon
(Penrose
&
Hameroff)
–
Hypothesis:
Neuron
microtubules
within
neurons
support
quantum
superposi,ons
(non-­‐computable
behaviour)
+
macroscopic
quantum
entanglement
across
brain.
• Highly
controversial
–
decoherence
counter-­‐argument!
• Physical
collapse
of
quantum
wavefunc,on
of
microtubules
essen,al
for
consciousness
(Orch-­‐OR).
23

24. Complex
Dynamical
Behaviour
Theory
of
Mind
• Intrinsic
non-­‐linear
dynamics
of
each
individual
neuron
+
network
dynamics
(aUractors,
bifurca,ons
of
behaviour,
small
changes
in
inputs
lead
to
large
changes
in
outputs).
• ‘Simple’
non-­‐linear
models
found
for
behaviour
of
individual
spiking
neurons
→
reproduce
complex
burs,ng
behaviour.
• Apparently
non-­‐algorithmic
behaviour
(some,mes
chaos)
from
algorithmic
(determinis,c)
components.
• Consciousness
as
an
emergent
phenomenon
from
a
neural
network
complex
dynamical
system
of
the
physical
brain.
24

25. Are
you
sure?
• An
underlying
level
of
reality?
• Quantum
state
decoherence
and
gravitons?
• Non-­‐linear
quantum
theory
• The
classical-­‐quantum
divide
-­‐
looking
for
decoherence
• To
be
con;nued…
25

26. THANK
YOU!!!
26