Re: IS high energy physics real ?

From: Paul Draper (pdraper_at_yahoo.com)
Date: 10/05/04 

Date: 5 Oct 2004 10:31:23 -0700

eighth@libero-dot-it.no-spam.invalid (eighth man) wrote in message news:<415f1eaa$1_1@127.0.0.1>...
> I have a few questions:
>
> 1) I read that particle physics uses
> accelarators and computers to compare
> results according to Feynman diagrams.
> According to the precision these diagrams
> may be 70 or 40000 and eventually millions
> to trillions all very complex to calcuate.
> At what point (decimal point;) will scientists
> think the precision will be enough ? (a trilllion
> feynman diagrams?) And if so will they be
> even able to calcuate it ? and even after won't
> they be curious to know if a higher precision
> could lead to something else ?

Usually the problem in experimental particle physics is separating the
signal from the noise. By far and away, most particle collisions are
mundane, which is to say that the differences between one event and
the next are so small that it's impossible to distinguish them either
experimentally or theoretically. What you need in particle physics is
a "stand-out" experimental signature, a signal way above noise.
Normally that points to the simplest possible Feynman diagram(s). On
the other hand, just checking the simplest diagram doesn't tell you
much about the theory. So you try to look at the next, slighly more
complicated signal. Unfortunately, for this kind of event, you may now
have a handful of Feynman diagrams that all could lead to the same
outcome, and you have to add them all up to get a prediction of what
you see. For the next, slightly more complicated event, which is an
even better test of the theory, all of a sudden you are in a world of
hurt, with hundreds of diagrams all contributing to the same kind of
event, and they all have to be added up. And so, calculating an event
with hundreds or even thousands of contributing diagrams is not really
that detailed a look at the theory --- it's combinatorics that bites
you in the ***.

>
> 2) after the grand theory of everything is
> achieved maybe 300 years from now, will
> scientists still study all the theoretical structures
> anyways even if it has no use for physics anymore ?

I have my sincere doubts that there will ever be a grand theory of
everything, even though that term (TOE) is bandied about freely.

>
> 3) particle accelarators, theories, computers
> etc. seem quite distant from reality... it makes
> me think sometime"is it real ?"
> I mean there is only one level seperating a
> virtual reality program from reality (the program)
> whereas in particle physics we have about 5 or 6
> (accelerators, theories, computers, calcuations etc)

Let me put it to you this way. The only force we know how to exploit
is electromagnetism. And our understanding of electromagnetism is only
100 years old. But virtually *all* of our existing technology --
electric circuits, chemistry, optics, semiconductors, robotics,
computers -- is based on our exploitation of electromagnetism. There
is, I would dare say, nothing you can point to in your TV set or iPod
that isn't based on what we've learned about electromagnetism in 100
years. In many cases, those steps are also 5 and 6 removed, but reside
squarely in electromagnetism anyway. Now, 100 years ago, I'm sure that
a lot of folks wondered what the point of all that work in E&M was.
But you have to understand it before you can use it.

OK, so here's the teaser. The next force we're getting a grip on is
the strong nuclear force, which is inherently a million times stronger
than the electromagnetic force. Still think we should stop work
understanding it?

(By the way, some folks would argue that we also have gravity
harnessed. Balderdash. If we didn't happen to have a fairly huge
source of gravitational potential nearby, we'd be hosed.)

PD