🚀 go-pugleaf

island <3FAF95DD.B8DEE52D@sundial.net>...
CUT


We do not know what physical principles govern the fundamental theory, In
developing general relativity, Einstein was guided by a principle he had
inferred from the known properties of gravitation, the principle of the
equivalence of gravitational forces to intertial effects such as centrifugal
force.

The development of the Standard Model was guided by a principle called gauge
symmetry, a generalization of the well known property of electricity that it
is only differences of voltages that matter, not voltages themselves.

But we have not discovered any fundamental principle that governs M-theory.
The various approximations to this theory look like string or field theories
in spacetimes of different dimensionalities, but it seems probable that the
fundamental theory is not to be formulated in spacetime at all.

Quantum field theory is powerfully constrained by principles concerning the
nature of four-dimensional spacetime that are incorporated in the special
theory of relativity.

How can we get the ideas we need to formulate a truly fundamental theory,
when this theory is meant to describe a realm where all intuitions derived
from life in spacetime become inapplicable???


The other obstacle is that even if we were able to formulate a fundamental
theory, we might not know how to use it to make previsions of the Standard
Model have been based on a method of calculation known as perturbation
theory.

In quantum mechanics, the rates of physical processes are given by sums over
alla possible sequences of intermediate steps by which thre process might
occur.

Using perturbation theory, one first considers just the simplest
intermediate steps, then the next simplest, and so on.

This works only if increasingly complicated intermediate steps make
decreasingly large contributions to the rate, which is usually the case if
the forces involved are sufficiently weak.

Sometimes a theory with very strong forces is equivalent to another theory
with very weak forces, which can be solved by the  methods of perturbation
theory, This seems to be true of certain pairs of the five string theories
in 10 dimension and the field theory in 11 dimensions.

Unfortunately, the forces of the fundamental theory are probably neither
very strong nor very weak, ruling out any use of pertubation theory.

It is impossible to say when these problems will be overcome, They may be
solved in a preprint put out tomorrow by some young theorist. Theymay not be
solved by 2060, or even 2200.

But when they are solved, even though we cannot do experiments at 10^16 GeV
or look into higher dimensions, we will not have any trouble recognizing the
truth of the fundamental unified theory.

The test will be whether the theory successfully accounts for the measured
values of the physical constants of the Standard Model, along with whatever
other effects beyond the Standard Model may have been discovered by then.

It is possible that when we finally understand how particles and forces
behave at energies up to 10^18 GeV, we will just find new mysteries, with a
final unification as far away as ever.

But I doubt it. There no hints of any fundamental energy scale beyond 10^18
GeV, and string theory even suggest that higher energies have no meaning.

The discovery of a unified theory that describes nature at all energies will
put usin a position to answer the deepest questions of cosmology: Did the
expanding cloud of galaxies we call the bing bang have a beginning at a
definite time in the past???

Is our bing bang only one episode in a much larger universein which big and
little bangs have been going on eternally?????

If so, do what we call the constants(or even the laws) of nature bary from
one bang to another?

This will not be the end of physics. It probably won't even help with some
of the outstanding problems of today's physics, such as understanding
turbulence and high-temperature superconductivity.

But it will mark the end of a certain kind of physics: the search of a
unified theory that entalis all other facts of physical science.

bye