marcus said:
On friday 23July Penrose new book came out
"The Road to Reality"
[a related lecture] series was called
something like "Fashion, Faith, and Fantasy in the New Physics of the Universe"
http://www.princeton.edu/WebMedia/lectures/
(scroll down to October where the menu lists the 3 Penrose talks)
this is similar to the title of the public lecture he gave in Dublin on
Friday, the day his book hit the stores.
...
I listened to these Penrose lectures. The first one, called "Fashion", had some criticism of String theory as I recall. But it was good humored, I thought, and neither severe or polemical.
But Lubos Motl, who tends to take issue with critiques of String, has just posted this in sci.physics.string. It suggests to me that Lubos expects from Penrose more partisanship than I thought Sir Roger actually expressed.
Lubos is responding here to a post from Daniel, not to actual words by Penrose. (But he refers to Penrose as if Penrose had made criticisms of String)
The title of Lubos post is "Re: Penrose critique of string theory"
-------exerpt from Lubos post-----
On Sat, 31 Jul 2004, Daniel wrote:
> Roger Penrose offered a lecture on string theory title "Fashion,
> Faith, and Fantasy in Theoretical Physics".[/color]
Let me first say that Roger Penrose has done a large number of
contributions to physics and thinking and many of them are being intensely
used and studied especially by string theorists - for example twistors;
causal diagrams; pp-wave limits of geometries; cosmic censorship, and so
on.
We all admire his talent and his precious insights. I am pretty sure that
if he decided to study current physics seriously - instead of thinking
(like an overly speculative fan of physics) about gravitational collapses
of the wavefunction in the brain and instead of giving shallow lectures
inspired by science like this one, he might become a tough competitor for
some of the current leaders of theoretical physics, including Edward
Witten.
> [RP] apparently is critical of string theory, and prefers loop quantum
> gravity.[/color]
Well, Roger Penrose anticipated the emergence of spin networks in quantum
gravity, which eventually occurred in loop quantum gravity. On the other
hand, although his insights are valuable for string theorists, none of
them is truly string-theoretical.
> polemic aside, what are his criticisms of string theory, how has
> string theorists responded, including edward witten and lubos motl,[/color]
Honestly, I find it inappropriate to appear in the same sentence as Edward
Witten who has done more than me for science by several orders of
magnitude, but let me assume that your point was different. It would be
great if Edward Witten responded, too.
> and why does he think LQG is preferable?[/color]
It may be a good idea to ask him, and of course, he will be always welcome
if he appears on this newsgroup. ;-) If you ask me and you want to know
what I really think, the real reason behind this preference may be that he
might be viewed as a grandfather of loop quantum gravity, but he has not
contributed much to string theory.
...
...
[read the whole Lubos post in SPS]
...
...
> so there are some diehard believers who will give you elaborate
> specious arguments why it is impossible that any of the newer
> approaches to quantizing gravity can work[/color]
It would be more interesting scientifically if Roger Penrose could take,
for example, my 25 kilobyte long (devastating) review of Rovelli's new
book (to appear) which is also an analysis of the whole field of LQG and
if he showed which arguments against this "newer approach" may have a
loophole. Instead, Penrose seems to believe that he can influence the
direction where physics goes without any arguments. I am not sure whether
the overlap between science and religion is *that* far-reaching.
> and it lives in a kind of fantasy realm, making no testable
> predictions and ungoverned by experimental evidence, so the
> researchers indulge in untrammelled mathematical inventiveness[/color]
On the other hand, this statement is not original at all. String theory is
the most conservative extension of the successfully tested principles of
modern physics, and all its features are - at least qualitatively - very
physical and realistic. It is a rich theory but all of its different
phenomena will remain to be highly interesting and important mathematical
subjects to study.
> finally such an embarrassing richness of possibilities has emerged
> that the distinct variations of the theory have been estimated by its
> insiders (Susskind, Douglas) at ten-to-the-100 different base states
> and things like the Anthropic Principle, a latterday Hand of God, are
> being invoked in a desperate effort to find the right one.
> So it has gotten bogged down in its own fecundity.[/color]
We have discussed these questions a lot on this board. If the number of
possibilities to create a Universe - including working cosmology - in the
correct theory *is* that huge, we will have to live with this fact. String
theorists don't agree yet whether the usage of the Anthropic Reasoning
will be necessary. Many of us hate it. But it is a logical possibility. At
any rate, as long as theoretical physics exists as a field, the scholars
in it will study something. Because they have no new experiments, they
must study more or less pure theory. String theory remains the most
promising game in town, perhaps the only game in town. This might
hypothetically change - but only if someone found something equally (or
more) interesting. It cannot change by political speaches without
scientific content, even if the speaker is as famous as Roger Penrose.
------end quote from Lubos----
this is a sample, the whole post is at sci.physics.string
did Penrose actually make a substantial critique of String in his book or in his "Fashion" talk at Dublin this month? If so, what was the critique---what were the actual points?
awkings Universe, I sought out some of his books, which introduced me to his : Emperor's New Mind (which actually blew my mind a little !)..I then found some great online links, included the lectures which marcus highlighted, having seen then some time ago, I will be revisiting them, but I have to comment on the book review in your above post.
