On 4/22/2015 2:45 PM, Thomas Johnston wrote:
> But two theories are not better than one, as regimented attempts
> to understand things. I think the underlying intuition which pushes
> physicists towards a unified theory... (01)
Tom, physics is the *worst* example. Almost nobody ever uses the
most general theories. For any particular example, they *always*
use a special-case approximation that is tailored for that example.
And most of them, even for the same project, are *inconsistent*
with one another. (02)
Physicists have known for over a century that Newtonian physics
is only an approximation, but it is still the most widely used
theory. But even then, there are huge numbers of special cases
of Newtonian mechanics: supersonic fluids; subsonic fluids;
turbulent flow; viscous flow; incompressible fluids (which really
aren't). The biggest examples are the incredible number of
approximations for computing the global weather -- different
versions for multiple levels of the atmosphere, different regions
of the earth, different terrains, geographies, ocean currents,
times of day, seasons of the year, etc., etc., etc... (03)
The total number of widely used approximations is in the thousands.
The number of detailed approximations is in the billions -- every
engineer for every project takes a large number of general-purpose
approximations and specializes them for different parts of the project. (04)
Every large system -- ranging from your cell phone to your car to the
trains, planes, and road systems you use every day -- is based on a
large collection of mutually inconsistent approximations to the basic
laws of physics -- all of which are *known* to be false when pushed
to the limits. (05)
Fundamental principle: The human brain is the most complex natural
system known. It is far more complex than the global weather, the
Large Hadron Collider, or the global collection of all the human
constructions on earth. (06)
Analogy: The Greek theories of the cosmos by the pre-Socratics
are closer to modern physics than any current theory of the brain
is to the way it actually works. (07)
John (08)
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