Transcript Talk ()

Reflections and the Future of
Physics
July 28, 2009
Hong-Yee Chiu
Former Astrophysicist,
NASA Goddard Space Flight Center
Physics in 1959 (my Ph. D. Year)
• Main thesis work: 200 MeV π-p scattering
• Status: First satellite launched, laser just
invented, QED was just developed, parity
violation just discovered, General Relativity (GR)
considered a weird science, more particle
discovered as accelerators became larger.
• Astrophysics was in infancy, stellar evolution
was in development, no supernova theory;
neutron stars, black holes were speculative
objects.
• No comprehensive particle theory,
• ……
In 2009
۩Particle physics – experiments move from
laboratory to center of mass systems (collider)
۩A semi complete standard model
۩Satellites and lasers everywhere, GR in
vogue, particle species almost complete but …
۩Astrophysics among the most pursued
۩Neutron stars, black holes confirmed, dark
matter and dark energy discovered
۩Planetary system in other stars
…..
Where do we go from here?
• The last collider was just built (United
States already quitted) Tough luck if it fails
to achieve its objective
• Particle model and theory still incomplete –
need quantum gravity
• Steve Weinberg: not possible before 2050
(in time to welcome the retirement of
current generation of physicists)
• Too optimistic. The approach taken so far
is “not even wrong!”
String Theory dominates
• Lee Smolin: in The Trouble with Physics
he wrote: The Rise of String Theory, The
Fall of Science, and What comes next?
• Key point. GR requires generalized
coordinates, and in Quantum GR (QGR)
even generalized coordinates are not
allowed, only relationships
• There are at least 105 string theories, all
require coordinates
• At best, a transitional theory
Why the fall of science?
• 21st century physics is tied to grants
• Grants and tenure are judged by peers.
• The peer group consists of special interest
groups, so the trend propagates (look at
the U. S. democracy, dominance of
lobbyists and special interest groups).
• There is virtually no possibility for another
Einstein. He could never get a grant and a
tenure position. (Not even a job in patent
office – cutbacks, over committed.)
• So special interests win, science loses.
Look back at 19th century science
• In 1846 Uranus was discovered based on
Newtonian mechanics and mathematics
• By early 20th century, confidence was so
high, Lord Kelvin claimed that physics was
almost complete, except two dark clouds –
Roentgen’s X-ray, Becquerel’s natural
radioactivity … the rest is history
• The great Titanic was built and the faith on
engineering reached pinnacle – a lesson
we never forget ever since.
A sister science - mathematics
• Early20th century, mathematics was at pinnacle
• Basic concepts were formed – Dedekind cut,
Peano theorem, …
• David Hilbert posted 23 most important
mathematic problems to be solved
• Now, around 5 problems remain unsolved
• The 6th problem: To axiomatize all of physics,
probably was an illusion. Even mathematics
itself could not do it (Gődel, Cohen): There are
limits in the power of mathematics. To
axiomatize was the dream of the so-called
rational mechanics.
Early 21st century
• Clay Institute (Cambridge, Mass) posted 7
problems with million dollar prizes. Only
two from Hilbert’s list made it (Riemann
Hypothesis) and Poincaré’s conjecture,
which has since been resolved (prize
declined)
• Two are of vital interest to physicists
• 5 Yang–Mills existence and mass gap
• 6 Navier–Stokes existence and
smoothness
Center of gravity moved to applied
mathematics
• Game theory takes preponderance,
because it deals with human behavior and
social problems. Examples:
• Prisoner’s dilemma (solution known, no
analytical proof) – commercial application
• Arrow’s impossibility theorem (no fair
election if there are more than two parties)
(received Nobel prize in economics)
• Cocktail party problem
Prisoner’s dilemma
• Two prisoners A and B were caught, no hard
evidence of crime
• If A and B both keep silent, they will be
released because of lack of evidence.
• If A confesses that B is the leader, A receives
less sentence. Same is for B.
• If both A and B confess and accuse each
other, they both receive hefty sentences.
• What should A and B do?
• No analytical solution – only practical solution
Applications
• A and B want to exchange merchandise X and Y.
• A and B are honest, they get rewarded X and Y.
• A is dishonest, A gains and B loses and vice
versa.
• Both A and B dishonest, both lose.
• Let A be supermarket B is customer, the game
becomes a model for business
• Almost all MBA schools requires the exercise of
prisoner’s dilemma.
Practical solution
• Computer simulations: Supermarket A is
honest, but keeps an eye on customer B.
Occasionally A will issue coupons and
discounts. If B is honest, he/she will have
a good place to shop with frequent
discounts. If B is dishonest, A seeks
maximum punishment. (A dishonest, folds)
• Conclusion: Golden rule “Give your left
cheek” does not work.
• Silver rule works: Confucius: Repay
kindness with kindness, use justice to
punish the offender.以德報德,以直報怨
Cocktail Party Problem
• You passed by a cocktail party, and was
invited to step in. you need to decide.
• A passerby said, sure, you know A, B …
and you should join.
• Another said, wait, you do not know A, B
… too well maybe you should not.
• You need to make a decision: You might
have a good time in joining but you might
end up wasting a whole evening.
• Application: Risk analysis. (Should you
buy a certain stock? Get married?).
There are many other applications of
game theory. Many patents have been
filed to deal with practical matters, even in
divorce cases. Sociologists try to
understand the so-called tipping point
theory – New York City used to be crime
ridden, suddenly the crime rate dropped
from 1st to 163rd. Why and how?
Something caused the tipping of the scale.
This is a yet unsolved problem.
Examples of Unresolved Physics
• Defense of Quantum physics and GR
• Their conclusions are absolutely (well,
almost) correct; we know about quantum
physics. How about GR?
• Global Positioning System GPS is an
example of how GR works. To get within 1
meter, one needs perhaps 10-14 accuracy,
to get within 1 cm, one needs maybe 10-17
accuracy (this could be the limit). GR
effect creeps in at 10-10.
Difficulties
• For quantum physics, it is the well known
Einstein–Podolsky–Rosen (EPR) paradox.
• If not fixed, the theory does not have the
final say – it lacks self consistency.
• For GR, it is less well known that GR has
solutions that violates causality.
• In Gődel’s rotational universe, the light
cone tilts toward past after the velocity of
light circle: v>c. This makes it possible to
time travel to the past.
Frank Tipler Cylinder
• Frank Tipler showed in 1974 that it is
possible to tilt the light cone towards the
past around an infinite cylinder of dense
matter. Several fictions have been written.
• Problems with time travel to the past and
future: Violation of causality.
• Uncertainty principle no longer valid.
• GR thus contains solutions that violate
causality and uncertainty principle.
• This and other difficulties must be
resolved.
Unsolved simpler problems
• Two examples.
• Properties of soliton waves: a soliton wave
acts like a particle and is resistant to
dispersion.
• Ordinary photon can travel in optical fiber
for about 20 km.
• High powered source which bundles many
photons together to become a soliton can
travel over 200 km, making transoceanic
fiber optic communication possible. (This
is an empirical discovery.)
Boiling point calculation
• There is no theory to accurately calculate
the boiling point.
• Even the simplest case, the boiling point of
liquid helium has not been accurately
calculated. (Helium is almost perfect gas.)
• The soliton problem and the boiling point
problem are possibly related to the
understanding of the Navier Stokes
equation (one of the Clay Institute
problems.)
• One never gets a grant for these
problems.
The future direction?
• Probably no higher energy colliders in the
future.
• It is impossible to compete against
industry on specific applications.
• Lesson: By rejecting applied mathematics
early in the game, most mathematics
departments have been reduced to service
departments, teaching undergraduate
math.
• Future? One should search for new
frontiers within the realm of old physics.