In article ,
Bilge wrote:

Diego Feliciano:

John Baez wrote:

There is not one whit of experimental evidence for either string
theory or loop quantum gravity, and both theories have some serious
problems, so it might seem premature for philosophers to consider
their implications. It indeed makes little sense for philosophers to
spend time chasing every short-lived fad in these fast-moving
subjects. Instead, what is worthy of reflection is that these two
approaches to quantum gravity, while disagreeing heatedly on so many
issues, have so much in common. It suggests that in our attempts to
reconcile the quantum-theoretic notions of state and process with the
relativistic notions of space and spacetime, we have a limited supply
of promising ideas. It is an open question whether these ideas will
be up to the task of describing nature. But this actually makes it
more urgent, not less, for philosophers to clarify and question these
ideas and the implicit assumptions upon which they rest.

Generally I'm not one who easily is swayed by fads but string theory
has indisputable merits. I've read voluminous papers on the matter and
would be happy to point you to my sources.

I think you misunderstood his point, which as I understand that
paragraph, has nothing to do with potential merit, but with the
(mostly) undisputed fact that string theory (and loop quantum gravity)
have no experimental evidence to support them.

Exactly. And I was saying this because my article was addressed
to philosophers of physics, who might not know this. I wanted to
tell them that:

a) there's no experimental evidence for strings, loops or any other
theory of quantum gravity,

b) so, philosophers of physics shouldn't feel the need to keep up
with every detail of these theories,

c) but still, they shouldn't be scared to learn a little about strings
and loops, because these theories actually have a lot in common - so
that regardless of whether they're *right*, they have a lot to say
about turn-of-the-millenium physicists think about the universe....
which is something philosophers of physics should find interesting!

You see, philosophers of physics have trouble keeping up with all
the latest papers on the arXiv, and they don't want to draw big conclusions
based on theories that turn out to be wrong. So, they tend to study
older theories that already have lots of experimental support.

This is fine, but it would be more fun if philosophers got interested
in physics questions where the answers are still unknown, where even
the questions are still murky, and help us think about these questions.

I'm trying to lure them into the deep end of the pool!

Some people have expressed skepticism that philosophers could be of
any help in physics, but such people probably don't know how smart
some philosophers of physics are. They probably have in mind some
cliched image of a philosopher who answers every question with another
question, or a discussion-crushing remark like "Define *truth*!".
In fact, there are some really smart folks like Julian Barbour and
John Earman, who are already swimming in the deep end. I just want more!

Anyone interested in the philosophical questions raised by
quantum gravity should read this book:

Physics Meets Philosophy at the Planck Scale:
Contemporary Theories in Quantum Gravity
edited by Craig Callender and Nick Huggett
Cambridge U. Press, 2001

http://www.amazon.com/exec/obidos/tg...99422-2289645?

So far, string theory
does not make any testable prediction which have not already been
explained without string theory (I know more about strings than loop
quantum gravity, but I assume the same is true for loop quantum
gravity).

It's true there too - despite some interesting work relating
loop quantum cosmology to the WMAP data.

String theorists often point out that string theory predicts
gravity (or more precisely, seems to require it), but obviously there
is no string theory which describes gravity in the correct context of
the other forces in the universe. If there were, no one would still be
trying to find a theory which unifies all of the fundamental interactions.
Personally, I have no problem believing that string theory has the
potential to serve the purpose for which it exists, but that doesn't
alter the fact that there is currently no evidence for it.

Right, exactly. It's good to be very clear about things like this.

John Baez wrote:


Right, exactly. It's good to be very clear about things like this.

May I take this opportunity to thank you for you input. You are truly
one of the few high points of the UseNet NG-s.

Bob Kolker

"Robert J. Kolker" wrote in message
news:nyaqc.68522$536.11082733@attbi_s03...


John Baez wrote:


Right, exactly. It's good to be very clear about things like this.

May I take this opportunity to thank you for you input. You are truly
one of the few high points of the UseNet NG-s.

Without doubt Bob, without doubt.

Thanks
Bill

"Bill Hobba" wrote

[friendly words addressing John Baez]
Without doubt Bob, without doubt.


Let me say thanks too for all his effort of sharing
wisdom and curiosity. I smilingly remember his last
tour de force thru number theory, where he seemed
to have read and understood more in some weeks than
I in all the years - and all that presented in a
lively manner. Let me give a small present, some
nice equation, I found out yesterday while pondering
about R_r and S_r and Chebyshev U(n,x) and all that:

oo
------ 2
\ k
/ ---- = 6
/ k
/_________ 2
k=1


Best regards
Rainer Rosenthal

In article ,
Rainer Rosenthal wrote:

Let me give a small present, some
nice equation, I found out yesterday while pondering
about R_r and S_r and Chebyshev U(n,x) and all that:

oo
--------
\ 2
\ k
/ ---- = 6
/ k
/_________ 2
k=1


That's very cute - I hadn't seen that!

The "6" gives it an eerie resemblance to the famous

oo
--------
\ 2
\ 1 pi
/ ---- = ----
/ 2 6
/_________ k
k=1

and it also reminds me of this one I recently ran across:

oo
--------
\ 2
\ 1 pi 1 2
/ ------- = ---- - - (ln 2)
/ 2 k 12 2
/_________ k 2
k=1

Thanks for your thanks - and Robert Kolker and Bill Hobba, too!
I love learning things and talking about them and it makes me
especially happy when I feel I've helped some other people find
some of the beautiful things that are lurking out there in the
universe.

As far as number theory goes, you should really thank James Dolan
for explaining a bunch of it to me....