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marcus

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-----Arun Gupta wrote---

Is physics reverting to religion?

[1]

Lubos Motl <motl@feynman.harvard.edu> wrote

> LQG is not string theory, and therefore it can't describe gravity.

Newton and Einstein have done fairly good jobs so far, describing

gravity without string theory. Yes, I know you mean a quantum theory.

[2]

But then demonstrate that there are no other routes to a quantum

theory of gravity, not mistaking mathematical difficulty for impossibility.

[3]

Or, following the usual route of physics, demonstrate experimental

results so distinct and compelling that possible competing theories are

of little interest.

Since neither of the above are available,

[4]

I can only interpret the attacks on people who seek gravity outside of

string theory as quasi-religious fervor.

It seems obvious that if you don't look, you can't find.

[6]

And ultimately, if the search fails, it will be a compelling argument in

favor of string theory, so why fear it?

[7]

If the search succeeds, it won't be a disaster for physics, as someone has

claimed.

[8]

-Arun

-------end quote from Arun, start quote from Lubos--------

1.[Moderator's note: This is the only off-topic message in this thread that

will be tolerated. Please find a newsgroup about religion if you

want to continue with this sort of non-string-theoretical discussion. LM]

2.[Moderator's note: Yes and no. I meant what I wrote. I wrote that LQG

can't describe gravity. LQG may be a quantum theory, but it is not a theory

of gravity. Yes, of course the constraint is that string theory is

the unique *quantum* theory of gravity. LM]

3.[Moderator's note: It may be mathematically *difficult* to prove that

string theory is the unique solution, but it does not mean that it is not

unique. This uniqueness may be hard to see for someone who knows very

little about string theory, but the more you will know about theoretical

physics and the possible inconsistencies in various candidate theories -

and the miraculous ways how string theory avoids these inconsistencies -

the more you will realize how true and deep my statement is and how

false and shallow is yours. LM]

4.[Moderator's note: The strategy that you propose is unscientific. It is

not necessary to disprove all conceivable alternatives to string theory

if we want to rule out LQG. It was enough to rule out LQG which was a

much easier task. LM]

5.[Moderator's note: if you learned some technical stuff instead of your

current philosophical/religious words, you might become able to do

better and find a better interpretation. LM]

6.[Moderator's note: I assure you that I look. Conversely, if you don't

look, you can't see the problems with *any* inconsistent theory. LM]

7.[Moderator's note: I don't fear anything. I just stated a rather

well-known insight about uniqueness of string theory among the known

quantum theories of gravity. It seems to me that it is *you* who fears

it. LM]

8.[Moderator's note: Anyone is allowed to search for anything, which does

not mean that all searches are equally justified and reasonable. LM]

----end quote----