# Penrose: Road to Reality, just out

1. Jul 25, 2004

### marcus

On friday 23July Penrose new book came out
Three hour-and-half lectures he gave on separate evenings
last October at Princeton are online and very likely
share key ideas with the book.

I will get the links for those lectures. The 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.

John Baez says the book is a 1000-page blockbuster

Baez just posted about the Hawking talk and other Dublin stuff on SPR.

Has anyone seen Penrose book, The Road to Reality?
Has anyone here besides me seen the Princeton talks?
they give a perspective on the short list of big issues in physics, Quantum Gravity, the big bang, time, the second law.

If you have a favorite big issue then watch the lecture (or read the book) and you will probably find Penrose discussing it.

Last edited: Jul 25, 2004
2. Jul 31, 2004

### marcus

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".

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.

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,

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?

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

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

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.

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?

3. Jul 31, 2004

### sol2

That's great Marcus.

But in context of Smolins issues in Three Roads to Quantum gravity one of these roads had to do with Penrose. This is part of the distilliation process that Smolin went through to garner his thinking to a position adopted?

http://www.scienceu.com/geometry/articles/tiling/images/per1.gif

One of the issues I tried to point out in the other thread, is the idea of supersymmetry, and how such thinking could have been given credibiltiy in how we saw Penroses Tessellations(dualism as a symmetry)). The supportive view is automatic, where one line, defines the existance of another perception.

The Particle Nature is quite informative here

I once called attention to it, "in line of shadow,line of light".

The alteration in our thinking is really quite amazing once we consider the work of Escher here, and many of his works.

Hee are a few other links for consideration here.

http://users.ox.ac.uk/~tweb/00006/s01.jpg

I look forward to reading his book and I hope is clear for a laymen like me.

Last edited: Jul 31, 2004
4. Jul 31, 2004

### meteor

A review...
http://news.scotsman.com/features.cfm?id=849142004

marcus, look this paragraph of the review:
"In the 1960s, he and Hawking proved that the ‘singularity’ of the Big Bang - when all space and matter were somehow shrunk to a point - was an unavoidable feature of general relativity"

But after all, who is Andrew Crumley?

Last edited: Jul 31, 2004
5. Aug 1, 2004

### Olias

Being a big fan of Penrose since I had first seen him in a documentary here in the UK called 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.

It seems to me that Penrose has produced a thorough expose on all things important, with different levels of intensity, just reading the review it seems along the lines of Isaac Asimov's trilogy: Understanding Physics, which I also have a copy of, but obviously is quite dated.

It may be a few weeks before I can afford the new Penrose book, but having had just a glimpse of Penrose and his insights, quite late, I had never heard of him until a few years ago, I know the book will be fantastic.

6. Aug 1, 2004

### meteor

It's not strange that it blew out your mind, as I'm actually reading "The emperor's new mind", and I find it mathematically much more challenging that all the popular books of Hawking. And the next book waiting in my "bookshelf" is its continuation, "The large, the small and the human mind"

7. Aug 1, 2004

### marcus

Two things meteor,

one is, that is a great review.
I am usually reluctant to buy expensive books as so much
that I want is available free on web but
this could be one of those I want to own.

It is not yet generally available in US stores
but can be ordered from UK, where it sells for 30 pounds sterling
when it becomes available in US later this month the list price is to be $85 However if one orders from UK it is more like$55, I see.
this is peculiar.

The other thing is that you and Andrew Crumley may well turn out to be right and the universe might be spatially finite and thus have expanded from a rather small place-----I am reluctant to say a point.

Since Omega is measured to be 1.02 +/- 0.2
it seems quite possible that it is something like 1.01
and space is finite (despite all my insistence to the contrary)
and not quite flat
and furthermore Smolin's model of universes budding off of black holes in other universes-----with which he offers to explain why the fundamental constants are what they are----would also give us a spatially finite universe.

I may have to reconcile myself to it not being infinite and flat.

However I steadfastly maintain that in the General Theory of Relativity singularities are not required to be points.

8. Aug 1, 2004

### speeding electron

I got the book as a birthday present a couple of days ago, but I haven't spent that much 'quality time' with it. Maybe the first third is devoted to some mathematical foundations, after which he proceeds at a scary rate through the developments in theoretical physics. Of course even given the length of the book he has to refer you to more specialist texts for things he has almost skipped over, resulting in quite an extensive bibliography.
Laymen resenting condescension will be happy - he goes straight in with the mathematical concepts, so that the book has a surprisingly complete feel. I haven't looked far enough in, nor am I sufficiently qualified to comment on his remarks about string theory, but I thought I should contribute since I seem to be one of the few owners. He does however leave plenty of room for his own opinions.

9. Aug 4, 2004

### marcus

I ordered "Road to Reality" last week and should have it by the end of this month. It does not seem to be available yet on west coast of US.
I would be glad if you would check in at this thread in a couple of weeks, as when i get my copy I would appreciate having fellow reader of the book.
for a first pass I will probably skip the technical detail and try to get a
feel for his intuition and philosophical hunches.

I must admit that one thing that prompted me to go ahead and order rather than wait for the book to appear in local stores, for browsing, was the resentful reaction of Lubos and his dismissing Penrose has having undergone a "decline" which I suppose is a reference to Penrose age. I took the Motlian hostility as a Good Omen suggesting that the book may be more than usually interesting.

Later I read the Crumley review which Meteor linked for us and it, again, provoked more than ordinary interest. I have high expectations particularly of the more hunchy parts (how Penrose sees developments in Quantum Gravity and the direction physics is going)

10. Aug 4, 2004

### sol2

Brazen Youths Disrespect To The Grandfathers?

Of course, you do not need my opinion on that matter either

So I'll look forward also to one of the discriptions of Three Roads of Quantum Gravity by Smolin, and what those twistors mean in his attempt at unifying Gr with QM.

Here is my contribution and any further informations sources or links, would be appreciated as you can see I am building too

Reading Smolins book, if you see it lying around might be a good thing to pick up for some perspective inthis regard? My site title was choosen because of the distilliation process Smolin so likes to do, after taking in a lot of information, not that I am speaking for him. It just seems to be his mode of operandi. His latest on Antropic article is a case in point.

In the mean time, a lot of prep work can be looked at, so that when the book arrives, we might understand this perception as well?

Maybe Lubos can point directly to his reasons for slighting as well so that we know where he might feel Penrose failed. Just a thought

Last edited: Aug 4, 2004
11. Aug 4, 2004

### marcus

12. Aug 6, 2004

### marcus

since 8:28AM this Friday morning (GMT-8)
the Penrose book has been number FOUR on the
bestseller list at Amazon.uk.co

http://www.amazon.co.uk/exec/obidos...stsellers/ref=cs_nav_sn_4/202-5121337-2949434

quite a remarkable performance on the part of the British bookbuying public and the book

it is after 2PM now so it has been up there for 6 hours
only topped by two diet books and the DaVinci Code

Peter Woit---Not Even Wrong---blogged about the book earlier, when BTW it was only #17 on the amazon list.
something about String Theory and the Emperor's New Clothes.
apparently "Road to Reality" is somewhat more optimistic about Loop Quantum Gravity than about String (but I cant say definitely since the copy I ordered hasnt come yet)

[edit: as of 5PM (GMT-8) Penrose had risen to 3rd place at amazon

http://www.amazon.co.uk/exec/obidos...stsellers/ref=cs_nav_sn_4/202-5121337-2949434

It is topped only a diet book and the DaVinci Code.

This means he is ahead of Michael Moore (#6) and Lance Armstrong (#15)
and the Alexander McCall Smith lady-detective novels.]

Last edited: Aug 6, 2004
13. Aug 18, 2004

### mal4mac

14. Aug 9, 2005

### PhilosophyofPhysics

Have you read The Road to Reality now? What did you think of it?

15. Aug 9, 2005

### marcus

As it happens I was reading selected parts of it just recently. In July when things were slow around here for 2 or 3 weeks.
Mostly I think I have not gotten as much as I expected from the book.
I use it as a kind "encyclopedia of math/physics" written by a talented explainer. I use it more as a reference work, rather then for a straight read-through.

What do I think of it? I think it is an excellent book, which I've now owned for over half a year and have found plenty of occasion to consult. Penrose does make things clearer and manages not to be dry. But for whatever reason (my own laziness may have something to do with it)---it has not been a total immersion for me.

16. Aug 10, 2005

I read some of it in Barn's and Noble's and damn it is a big book, and it cost $40! No way could I con my parents into buying that for me, even if I dealt the educational card. But from what I did read it looks very good. Read through the part about hyperbolic geometry, which is something on my level math wise, and I found it very informing. 17. Aug 10, 2005 ### εllipse It's$25 at Amazon. And only \$16 used. http://www.amazon.com/exec/obidos/t...103-1250377-5949452?v=glance&s=books&n=507846

18. Aug 11, 2005

### Severian596

It's worth mentioning that the book has a website here:

This site was intended to hold solutions to Penrose's problems in "The Road to Reality," but apparently high sales volumes and the attention demanded for more print runs has delayed them. Which brings me to the website's other section, corrections. You who purchased the book last year probably have an edition that has many errors, the corrections for which can be found on this page. Just fyi.

I look forward to reading this book! But I have no comments because I just checked it out from the library yesterday.

19. Aug 15, 2005

### Telos

20. Jun 11, 2007

### Hymne

Seems as if they have forgotten the solution site..
Anybody that knows another site where i can get the solutions?