The Cosmic Landscape: String Theory and the Illusion of Intelligent Design

by Leonard Susskind

In his first book ever, the father of string theory reinvents the world's concept of the known universe and man's unique place within it. Line drawings.

Genres: Science, Physics, Nonfiction, Astronomy, Popular Science, Space, Philosophy

416 pages, Hardcover

First published December 12, 2005

About the author

Leonard Susskind is the Felix Bloch Professor of Theoretical Physics at Stanford University. His research interests include string theory, quantum field theory, quantum statistical mechanics and quantum cosmology. He is a member of the National Academy of Sciences, and the American Academy of Arts and Sciences, an associate member of the faculty of Canada's Perimeter Institute for Theoretical Physics, and a distinguished professor of the Korea Institute for Advanced Study.

read more: http://en.wikipedia.org/wiki/Leonard_...

Reviews

[Manny · Rating 3 out of 5]

I had seen many references to this controversial book - among other things, it's quoted approvingly in Dawkins's The God Delusion - but somehow I didn't get round to reading it until this week. Despite the fact that it's sloppily argued and poorly written, I'm embarrassed to say that I found it unputdownable. If you also enjoy watching smart, opinionated people shooting their mouths off in public, you may well have the same reaction.

Susskind, writing in 2005, confidently promises to explain Life, the Universe and Everything. He is one of the founders of string theory and the phrase is in the title, so no prizes for guessing that it will be an essential ingredient. In a nutshell, his argument is as follows.

The rest of this review is available elsewhere (the location cannot be given for Goodreads policy reasons)

[Eric Malone · Rating 5 out of 5]

This book is one of the best physics/cosmology books I've ever read (read 3 times in fact). The most interesting parts, for me, were related to the Anthropic Principle and the discussion of the Landscape and Multiverse theories.

As I understood it the biggest issue was with the cosmological constant he discussed. If it were exactly zero, as Einstein believed, we would live in a "flat" (read: not-curved) universe and everyone would be OK with that. But better and better measurements show that the cosmological constant only appears to be zero...after some 120 decimal places it suddenly is not zero anymore. Why exactly this means our universe is "fine-tuned" for us to live in...I'm not exactly sure. I just understood the more surface level explanation of the weirdness of something that appears to be zero for 119 digits suddenly not being zero anymore. Like if the digits of Pi started repeating your phone number after a billion decimal places.

Other anthropic issues are discussed as well: why is our planet in Goldilocks zone, why are we so lucky to have a large moon to stabilize our rotation, why are we so lucky to have Jupiter sweeping up our solar system's debris, why is the life of proton so remarkably stable, why is the gauge constant exactly where it needs to be to enable chemistry to happen, and on and on. The combination of all these "coincidences" is what Susskind argues gives the APPEARANCE of intelligent design or a benevolent God tuning the dials on our universe. But string theory's multiverse allows such a mind boggling number of different universes with different physical laws that when we ask "Why do we live in a universe so perfectly tailored to allow us to exist?" then the answer becomes "Because obviously if we didn't then we wouldn't be asking the question." Why does our planet have liquid water and atmospheric oxygen??? Because if not, we'd be dead and never have asked the question in the first place.

At least that was my understanding of it.
eric

[Robin · Rating 1 out of 5]

This could be a useful book were it not written by a person who thinks so well of himself that he continually intrudes his unpleasant personality over the subject matter. Basically, he is telling us something that Hume told us, what, about 300 years ago, that the universe seems beautifully designed to allow life to exist (which leads some to propose the notion that it must therefore have been specifically and deliberately designed for us to live in) because we do in fact live in it. It's the only one we know about, so we think it was made for us. The reality of course is that we arose in it; it caused us, and we are its effect. Hume lacked the theoretical physics to explain it mathematically, but he was right. He must be right because the great Leonard Susskind says so.

Okay, that is me intruding my own unpleasant personality on the subject matter. The upshot is, screw this, I'm going to read Feynman.

[Nostromo · Rating 5 out of 5]

Това, което отличава Съскинд от повечето автори на научно-популярна литература, "сражавали" се на предните редици на научно-изследователския прогрес, е че той не се притеснява от егото си и от това, че Аз-ът му изпъква във всеки един ред на книгата. Напротив, освен, че ни зарежда с ударна доза научни достижения, той волно или не ни въвлича не в аулата на академичния свят, където са бляскавите фанфари и лустросаните речи, а директно в прашните, задни стаички на университетите, където са се сблъсквали цели светове от идеи и знания. Среща ни лице в лице с учени, които днес олицетворяват физиката такава, каквато е. С които е спорил, които често не са били на неговото непопулярно мнение, но които впоследствие са признавали пораженията си, така както и той е признавал своите в случаите, в които е грешал.

Тази книга не е систематизиран наръчник, който ще ви даде основите и ще ви изведе на по-високо ниво в разбирането на света, в който живеем - има достатъчно книги, които се справят повече от задоволително с тази задача. Тази книга има за цел да ви обрисува картината, каквато я вижда Съскинд - не дистанцирано, сухо и методично, а с жарта и енергията на дете, откриващо един нов и фантастичен свят от възможности. Което не значи, че е неразбираем и ще има да се лутате в разсъжденията му. Разказвателната форма увлича, а естественият път на разкриване на светогледа на автора дава още по-голяма яснота и нови гледни точки върху въпросите, които разглежда.

Затова, ако искате не просто да сте наблюдатели, а да съпреживеете страстта и екстаза на откривателя, Съскинд е точно за вас.

(http://thingnothing.blogspot.com/2014...)

[Bill Leach · Rating 4 out of 5]

- A review of Feyman diagrams, propagators and vertex diagrams.
- The fine structure constant (alpha = 1/137 or 0.007297351) is an important constant of nature. It represents the probability that an electron will emit a photon as it moves along its trajectory.
- Feyman developed Quantum Electrodynamics (QED) which predicts the probability of any event based upon the propagators and the vertex diagrams, and upon coupling constants such as the fine structure constant.
- Quantum Chromodynamics (QCD) is the theory of quarks and gluons.
- There are 6 quarks - up, down, strange, charmed, top and bottom.
- Only the up and down quarks form the stable nuclei.
- A proton is 2 u and 1 d: Charge is 2/3 + 2/3 - 1/3 = 1
- A neutron is 2 u and 1 d: Charge is 2/3 - 1/3 - 1/3 = 0.
- QCD is the theory of strong interactions where gluons tie the quarks together.
- The numerical constant governing the emission of gluons is called the alpha-QCD and is 100 times larger than the fine structure constant.
- Weak interactions are another part of the Standard Model. Nothing in QED or QCD explains how a neutron can emit an electron and become a proton.
- Quarks and electrons can emit w-bosons, as can the neutrino.
- One of the 2 d quarks in a neutron can emit a w-boson and become a u quark, turning the neutron into a proton. The w-boson then splits into an electron and an anti-neutrino.
- The Standard Model makes use of about 30 fundamental constants. Extensions to the Standard Model and cosmological theory bring the number of constants to over a hundred.
- All evidence suggests that the constants do not vary over the observable universe.
- Einstein thought the universe to be stable and determined that an extra term was possible under General Relativity that would represent a force that would counteract gravity, which would otherwise act to pull the universe together. He denoted this cosmological constant as lambda. Unfortunately this resulted in an unstable equilibrium.
- Hubble discovered that the universe is expanding and the cosmological constant could be set to zero.
- Quantum mechanics predicts that empty space will be filled with fluctuations where particle pairs are created and annihilated over very short times (billion-trillionth of a second). These short lived particles are termed virtual particles and represent a vacuum energy.
- Fermions, such as electrons, contribute negative vacuum energy while bosons, such as photons, contribute positive energy.
- The vacuum energy exerts a force that is indistinguishable from the cosmological constant.
- Calculations of the vacuum energy produce a result that is vastly larger than what would be consistent with the observable universe.
- Super-symmetry (fermi-bose symmetry) suggests that there is a boson corresponding to every fermion (and vice versa) such that the vacuum energy nets to zero. However, there is no super-partner for the electron or other elementary particles.
- There are no viable theories as to why the vacuum energy is essentially zero.
- Steven Weinberg: The Anthropic principle: Some property of the Laws of Physics must be true, because if it wasn't we would not exist.
- Calculations show that if the cosmological constant is much different from what is empirically observed, the universe would not be suitable for our existence.
- The Planck mass, time and length are described.
- The quantum jitters of space occur on the scale of the Planck length and time. The Planck mass turns out to be equal to the smallest possible black hole.
- To a physicist a vacuum denotes a space where physics can take place.
- The Laws of Physics depend upon the values of the physical constants of a space.
- A field is the result of the coordinated movement of particles. Each particle has an associated field.
- Physicists discovered that the Standard Model is mathematically inconsistent, but could be made consistent by adding the Higgs particle.
- The mass / inertia of particles depend upon the value of the Higgs field. The exceptions are the two massless particles - the photon and the graviton.
- In the 80's, String Theory looked to be an elegant theory that would merge the Standard Model with gravity. However, since then 3 problems have emerged:
1. The number of mathematically consistent versions increased dramatically, opening up a stupendous Landscape.
2. The models became increasingly complex and less elegant.
3. All versions produce a non-zero cosmological constant.
- The Cosmological Principle - the large scale structure of the universe is homogeneous and isotropic.
- The galaxies are receding with a velocity equal to the product of their distance and the Hubble constant.
- Three possible geometries for space: zero, negative and positive curvature:
1. If the mass density is great enough to reverse the outgoing expansion, it will distort space into a 3 sphere. This is a closed and bounded universe or k=1 universe.
2. If the mass density is less than what is required to close the universe, it is insufficient to reverse the motion. It distorts space into a hyperbolic geometry. The universe expands forever, or k= -1 universe.
3. If right on the knife edge, the geometry of space is flat and uncurved. The universe endlessly expands, but at a diminishing rate. This is the flat or k=0 universe.
- A megaparsec is about 3 million light years, or 30 million trillion km - a little more than the distance to our neighboring galaxy Andromeda.
- The Hubble constant is about 75 km/sec per megaparsec.
- According to Hubble's Law, the Andromeda galaxy should be receding at 50 km / sec, but is moving toward us due to gravity.
- It would take only 10 E-25 kg/m3 to reverse the outward flow of the galaxies. This is roughly 50 protons / m3.
- The average cosmic density is around 1 proton / m3.
- Therefore, we appear to be living in an infinite open (k= -1) universe.
- The mass of the galaxies can be determined from their movement. Each galaxy is 10 times more massive than all of the visible stars and gas. The remaining mass is almost certainly not made up of ordinary matter. It is termed dark matter as it gives off no light. Dark matter is likely composed of some new, heavy elementary particles that have not yet been discovered.
- When including the dark matter, the amount of mass in the universe appears to be 5 times too small to attain a flat universe.
Hubbel calculated the age of the universe from the distances and speeds of the recession of the galaxies. Unfortunately, he calculated a billion years and rocks had been found that were 2 billion years old.
- Modern calculations put the age of the universe at 10 billion years. However, there are stars that appear to be 13 billion years old.
- If the vacuum energy were to amount to 30 protons / m3, it would solve the 2 biggest problems in cosmology:
1. A small cosmological constant would result, giving a flat universe which is what we observe.
2. The repulsive force would cause the expansion of the universe to accelerate. Run backward, the age would be calculated at 14 billion years, consistent with the ages of the stars.
- Type I supernovae always generate the same luminosity, and so observation gives both the distance and the rate of recession. The more distant supernovae are older, because of the time it takes light to reach earth. We observe a larger Hubble constant for older supernovae. These show that the expansion of the universe is accelerating. The value of the cosmological constant is just what Weinberg had predicted.
- The oldest light reaching earth has been Doppler shifted to microwave frequencies. The Cosmic Background Radiation (CMB) is very cold at 3 deg K.
- When detected from high altitude balloons, oscillating blobs can be seen. These are well enough known in theory that their size is known. Comparison of their known sizewith their apparent size allows measurement of a triangle and establishes that space is flat on scales of 10-20 billion light years,
- It appears that the universe inflated exponentially for a period in its earliest phases, and this has resulted in the surprisingly homogeneous nature of space.
- While expansion of the universe results in decreasing density of matter, that is not true of vacuum energy which is constant per volume of space.
- A chapter on the Anthropic Principle, how it requires a landscape of possible universes, and whether it is a valid scientific theory.
- Hadrons are the particles made up of quarks, anti-quarks and gluons.
- All hadrons belong to one of three families - baryons, mesons and glueballs.
- Baryons include protons and neutrons, and are made up of three quarks connected by strings.
- Energy can only be added in discrete steps.
- Mesons are made up of a quark and an anti-quark joined by a string.
- Glueballs are closed strings and can be formed when the quark and the anti-quark of a meson connect.
- A point particle moving through space-time gives a world line.
- A meson moving through space-time gives a world sheet and a close string gives a pipe. Junctions result where particles combine or separate.
- Particles exchange gluons so these sheets are made up of a fabric of lies representing the exchanges.
- String Theory requires 9 + 1 dimensions.
- Forces are the result of exchanging particles:
gravity - graviton
electromagnetic - photon
weak nuclear - pion
strong nuclear - gluon
- The strength of the forces depends on the mass of the messenger particle.
- The strings of String Theory vibrate at all modes (harmonics) of oscillation due to the quantum jitters. They appear to oscillate to the ends of the universe.
- String Theory was originally developed to describe hadrons. However, it has been expanded to describe all particles and forces, including gravity.
- Leptons are fermions that do not have strong interactions like quarks.
- Compactification - some dimensions are closed and compacted towards the size of the Planck length.
- Some particles move only in the compacted dimensions. Strings can be wound once or more around a compact dimension (winding number).
- The distance around a compact dimension is termed the winding scale, and is typically a few Planck lengths.
- The compact scale fixes properties such as the electronic charge and the masses of the particles. In effect, the compact scale determines the Laws of Physics.
- The 6 compact dimensions are rolled up in what are called Calabi-Yau spaces. Millions of possible C-Y spaces exist.
- The parameters that determine the shape of the C-Y spaces are called moduli, and number in the hundreds.
- The spaces can taper so that the dimensions vary from point to point. This is equivalent to saying that the Laws of Physics vary from point to point. Thus the C-Y spaces allow a Landscape of possibilities.
- Super symmetry is a concept whereby each fermion has a boson twin and vice-versa. However, there is no twin observed for the electron and other proposed particles do not appear to exist.
- Distortion may cause the twin partners to be different, perhaps very heavy. It may be that super symmetry may yet be applicable.
- Branes are membranes - 0-branes are points, 1-branes are surfaces, etc.
- String Theory may involve multi-dimensional branes that are compacted into the extra 6 dimensions.
- Fluxes, akin to fields, are now included in String Theory.
- de Sitter described an exponentially growing space. It would feature an event horizon representing the furthest distance at which points could be observed.
- Eternal Inflation is the idea that islands of vacuum energy form in an inflating meta-stable de Sitter space.
-These islands or bubbles could have Laws of Physics corresponding to any of the possibilities given in the Landscape of String Theory.
- The many worlds idea is that parallel universes have formed in these bubbles. This is the mega-verse.
- A review of complementarity and the Holographic Principle as applied to black holes.
- A review of various contemporary physicists and their views on String Theory and the Anthropic Principle.
- Susskind says that there are no serious alternatives to String Theory. Lee Smolin has a Loop Gravity theory but it may be an alternate formulation of String Theory, rather than an alternate theory.
- Many dislike the Anthropic Principle because it is too easy and may be akin to giving up. It may reduce the drive to explore more deeply.
- That the laws of nature are emergent is the idea of Robert Laughlin. He pictures a universe composed of a material like superfluid helium where the properties emerge only at the macroscopic levels. However, black holes do not work with this theory and Laughlin argues against some of the generally accepted properties of black holes such as Hawking radiation.
- Lee Smolin proposes a natural selection of universes whereby baby universes form inside black holes which are inside universes, etc. This repeated replication results in an evolution toward maximally fit universes.
- One problem with the Landscape is that String Theory loses it's predictive power. There are too many valleys in the Landscape to predict, for example, the mass of the top quark.
- Early inflation of the universe resulted in vacuum energy being converted to heat and particles. It is also theorized that some vacuum energy was converted to vast collections of entangled strings. These strings would not be visible as light or other electromagnetic radiation, but they would emit gravity waves. They may be detectable in the coming decade.
- Susskind sums up saying that there may yet be possibilities for testing String Theory that are not apparent today.

[Mallon Khan · Rating 3 out of 5]

How do you explain theoretical physics with no equations? lots of metaphors. Susskind runs the gamut on theoretical physics in the early 21st century. A whole new ballgame sine the 50's. Our scope of the cosmos has just widened to unprecedented proportions. Anything is possible, even *GASP* God!!

This is the guy that disproved Stephen Hawkins' theory of black holes. He went to write about it and wrote this book instead. Why? Because after a hundred years of sucking Newton's throbbing laws and licking Einstein's sweaty theory, pumping away chasing that ever allusive grand unified theory. The Physics community just realized we can only see less than 1% of the universe. 80% of space is "dark matter or dark energy" it effects us, but we can't see it or measure it. Coupled with the possibility of 10 other dimensions, doesn't it make you feel less than a Man. So much for that Grand unified theory.

Also see "Large Hardon Collider"

[Anthony Tenaglier · Rating 4 out of 5]

This book was hard to put down because the presentation of string theory was excellent. It was easy to follow and understand with wonderful analogies and descriptions. Still not sure on how to wrap my head around the idea of "compactification" though, as this is such an important tool in string theory. How can dimensions be reduced to "practically" nothing and still call it something theoretical????

The book was great though, until there was a "hiccup" at the end with his bragging about how he proved Hawking was wrong with information lost in a black hole and that his new radical idea of information being transmitted with the outgoing Hawking radiation was the solution. Not quite sure how that really fits in with String Theory... I imagine he wants you to buy his book on waging "war" with Hawking.

Also, I recommend his books over his lectures on iTunes University. His skills in teaching are far better in writing than what I witnessed in his classroom presentations.

[Ana · Rating 5 out of 5]

Absolutely beautiful popular science book, right up the alley of someone who really wants to understand physics but lacks even the minimal basics. Susskind writes an easy-to-follow prose, a thing to be appreciated given the scope and importance of his subjects. Found some great references to other authors/works that I'd like to follow up with.

[Charles Daney · Rating 5 out of 5]

This is quite a remarkable book. In 380 pages physicist Leonard Susskind gives a concise but easily understandable overview of a wide range of topics in physics and cosmology. The topics include basic quantum theory, quantum electodynamics (the theory of light, electricity, and magnetism), quantum chromodynamics (the theory behind nuclear energy), and general relativity (the theory of gravity). But that's just to get started on the main topic.

All of these topics are just the background for the big questions: How did the universe get started? Why is the universe the way it is, and in particular, how is it a suitable place for life as we know it? Is the universe that is now visible in our telescopes actually all that exists, or is it just a small part of an ensemble of many separate "universes" – a "multiverse"?

In order to describe a possible answer to those questions, Susskind first addresses, in the same concise, understandable way, other topics: string theory, the "cosmological constant" (also known as "dark energy"), and "cosmic inflation" (a once speculative theory that explains several otherwise susprising facts abou our universe). All of this just leads up to the book's real topics: the "anthropic principle" and the "cosmic landscape".

The anthropic priniciple is simply that whatever theory is used to "explain" the universe, the theory must be able to account for an indisputable fact: sentient, "intelligent" life exists. And not just any type of life. It must be our type of (human) life. That is: life based on the element carbon, which requires liquid water to function, and which takes a long time to evolve to what we're familiar with (probably a few billion years).

Despite its name, the cosmic landscape does not refer to the physical space we're familiar with. Instead it is an abstract space of extremely high dimension. How high? Quite possibly 10^500 (1 followed by 500 zeroes) dimensions. That is the abstract space of all independent parameters that might describe in full detail the exact topology (i. e. shape) of the smallest building blocks that make up the 9 spatial dimensions of string theory. (In addition to the 3 dimensions we can perceive, there are 6 more dimensions in the minuscule building blocks.)

What happened to string theory itself? Wasn't that supposed to be the "theory of everything"? The theory was tasked with accounting for the array of "fundamental" particles and forces of the "Standard Model", along with about 30 specific values for particle masses and force strengths that have been measured in high-energy physics experiments. What happened is that when it was realized such a huge number of independent parameters might be involved there was no obvious way to figure out how they determined the details of the Standard Model. String theorists kept hoping that some new mathematical principles would do this job, but after over 40 years of theorizing, absolutely nothing has turned up. String theory is a fine, consistent mathematical theory, but it doesn't (yet) explain basic physical facts.

This is where the cosmologial constant comes in. It is the added term in Einstein's fundamental equation of general relativity which, with no experimental failures so far, seems to perfectly describe the force of gravity – as a consequence of the curvature of 4-dimensional space-time. Einstein added it as a mere afterthought, hoping it could explain why the universe didn't collapse under its own gravity. That was misguided, but when it was determined (about 90 years ago) that the universe was rapidly expanding, the cosmological constant turned out to be essential in explaining the rate of expansion.

"Dark energy" is a form of energy that may permeate space that is perfectly empty of matter. It could be what is responsible for the cosmological constant. However, the cosmological constant has now been very accurately measured since 1998 by astronomical observations, and it is incredibly small compared to what is predicted by the Standard Model – about a factor of 10^120 too small. Alternatively, if a conjectured physical symmetry called "supersymmetry" exists and is not "broken", then the dark energy and hence the cosmological constant should be exactly 0. But that is most definitely not what is observed. And on top of that, there is so far no experimental evidence for supersymmetry that is either unbroken or just slightly broken.

Now, the cosmological constant as measured just happens to have almost exactly the right value for life as we know it to exist. If it were a bit smaller, the universe would have collapsed in much less than the roughly 4 billion years it has taken for our form of intelligent life to evolve. If it were a bit larger, the universe would have expanded too rapidly for stars and galaxies to form. In that case, neither carbon nor oxygen (needed for water) – which as far as we know are only formed inside stars – could exist. Stars are also (probably) needed for rocky planets with liquid water. And so, mysteriously, the cosmological constant seems to be almost just right as a necessary (though not sufficient) condition for our form of life to exist. Steven Weinberg had already noticed this about 10 years before an accurate measurement of the cosmological constant.

The idea of cosmic inflation was proposed 35 years ago (by Alan Guth) and is now accepted by most cosmologists, even though definitive evidence for it is still somewhat scanty. It's widely accepted since it does explain a lot, such as the extreme "flatness" and homogeneity of space. It's also a key ingredient of the cosmic landscape hypothesis. An extension of the inflation idea – "eternal inflation", due to Andrei Linde – proposes that not just our universe, but an unending series of "pocket universes" come into existence over time by basically the same mechanism as originally conceived. And in each of those pocket universes most physical constants, including the cosmological constant, can have random different values.

The cosmological constant is the key, since it may be the amount of energy in "empty" space. As an energy it can have almost any value. In almost all cases it is probably very large to begin with – much too large for our form of life to exist. But no matter how large it starts out, it can also drop rapidly by quantum tunneling into a lower energy level of the landscape, almost like water running downhill. However rarely this happens, the constant can become small enough for us, so here we are. Other physical constants of the Standard Model can also vary.

Another important constant is the "fine structure constant". It controls the strength of the electromagnetic field. This has to be right so that chemistry essential to life can occur. Another constant regulates the strong nuclear force, and it has to be right in order for carbon to form in stars (assuming stars exist in the first place). Besides those things, the strength of gravity (which is extrememly weak compared to other forces) has to be weak enough (together with the cosmological constant) so that the universe doesn't collapse almost as soon as it forms. And there must be other things that must be "just right" as well. (Martin Rees' Just Six Numbers: The Deep Forces That Shape the Universe is a good reference on this.)

The anthropic principle is a credible tool only if all the right conditions don't "just happen" at the instant a new pocket universe forms. There are just far too many variables (potentially 10^500) that have to be just right. So there needs to be a mechanism that allows a pocket universe to "evolve" over time to successively lower values of the cosmological constant (the energy of empty space). All possible values of each variable exist in the cosmic landscape by definition. However, hardly any are associated with existing pocket universes. But when there is a pocket universe in a particular state, to transition to a "nearby" state of lower energy, which will also have different values of all other variables, it can do so by the mechanism of quantum tunneling. Eternal inflation guarantees that there's enough time for an infinite number of pocket universes to exist. So, eventually, at least one but possibly infintely many will exist that could be like "ours".

Susskind's book was published in 2006. It's fair to ask what has happened with the cosmic landscape idea in the last 10 years. In that time there don't seem to have been any dramatic discoveries, comparable to the measurement of the cosmological constant, that either significantly add or remove support for the landscape idea. But, Susskind says, even in 2006 cosmologists mostly had a positive attitude toward the idea. That still seems to be true now, though there definitely are exceptions. The attitudes of physicists, however, were more mixed in 2006, and probably still are. Some physicists are still hopeful that eventually some new mathematical development may yet make it possible to construct a "theory of everything", based on string theory, that will be simple and elegant and nail down all of the variables to make a universe exactly like ours. Other physicists are exploring different theories that will, at least, unify gravity and quantum mechanics and also yield a universe like ours.

Yet many physicists do share Susskind's view. It's important to note that Susskind is not only a physicist himself, but in fact was actually the originator of string theory (although at least two others independently had similar ideas about the same time). However, Susskind gradually gave up on the possibility that string theory by itself could explain "everything" – in particular the exact values of all variables, leaving no arbitrary values that could be discovered only by experiment. Many physicists still pin their hopes on that possibility, somehow or other. But perhaps the multiverse and the landscape, however much they lack in simplicity and elegance, is how things really are.

There are, incidentally, several more recent books that also have good accounts of the landscape and the multiverse – Brian Greene's The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos and Max Tegmark's Our Mathematical Universe: My Quest for the Ultimate Nature of Reality, for example.

[Book Shark · Rating 4 out of 5]

The Cosmic Landscape: String Theory and the Illusion of Intelligent Design by Leonard Susskind

"The Cosmic Landscape" is an informative, provocative theoretical physics book about how the world came to be the way it is. Dr. Leonard Susskind takes the layperson behind the scenes of an on-going debate among physicists and cosmologists; it's a battle between those who believe that the laws of nature are determined by mathematical relations, and those who believe that the Laws of Physics have been determined by the requirement that intelligent life be possible. This book is educational and sometimes challenging but ultimately satisfying. This stimulating 416-page book includes the following thirteen chapters: 1. The World According to Feynman, 2. The Mother of All Physics Problems, 3. The Lay of the Land, 4. The Myth of Uniqueness and Elegance, 5. Thunderbolt from Heaven, 6. On Frozen Fish and Boiled Fish, 7. A Rubber Band-Powered World, 8. Reincarnation, 9. On Our Own?, 10. The Branes behind Rube Goldberg's Greatest Machine, 11. A Bubble Bath Universe, 12. The Black Hole War, and 13. Summing Up.

Positives:
1. A well-written, accessible book for the masses.
2. The fascinating topic of cosmology in the hands of subject-matter expert.
3. Even though the Dr. Susskind is obviously a string theorist he does a commendable job of being fair and even-handed.
4. Does a wonderful job of introducing the Laws of Physics to the readers at an enjoyable and accessible level. Dr. Susskind takes pride in educating the public on very difficult and esoteric topics. Very few equations, those of you math-adversed do not fret.
5. Explaining the theories that best explain the universe. "Inflationary cosmology, which is our best theory of the universe, is leading us, sometimes unwillingly, to a concept of a megaverse, filled with a prodigious number of what Alan Guth calls "pocket universes."
6. Despite the intellectual battles on contentious cosmological debates among scientists there seems to be a great deal of respect, honor and most importantly drive to find the answers to our biggest cosmological questions. Dr. Susskind is very complimentary to his brethren. An all-star cast of physicists. "I have always admired the clarity and depth of Steven Weinberg's physics. In my opinion he, more than anyone, can lay claim to being the father, of the Standard Model."
7. Making elementary particles accessible to the masses via Feynman's pictures.
8. The cosmological constant in perspective. Was it truly Einstein's "biggest blunder"?
9. Cosmic Landscape in proper context. "It denotes a mathematical space representing all of the possible environments that theory allows".
10. Elegance in science. "The best theory would be not only a theory of everything, but it would be the only possible theory of everything."
11. Is the universe finite and bounded as Einstein thought, or is it unbounded filled with an endless infinity of stars and galaxies? What is the geometry of space? Find out.
12. The great achievements of cosmology. "The connection between the quantum theory of the microscopic world and the large-scale structure of the astronomical and cosmological world is one of the greatest achievements of cosmology."
13. Dismantling intelligent design...always a personal favorite.
14. Stirring up the hornet's nest with "The Anthropic Landscape of String Theory". Dr. Susskind explains his baby, String Theory. Three chapters of everything String Theory.
15. In defense of the populated Landscape. "Mechanisms that rely on well-tested physical principles gave rise to a huge, or even an infinite, number of pocket universes, with each and every valley in the Landscape being represented."
16. The chapter on the black hole war covers beautifully the behind the scenes battle among scientists. Stephen Hawking eat your heart out..."If Gerard is conservative I would have to say that Stephen Hawking is the Evel Knievel of physics."
17. Really closes out the book with a bang. The Summing Up chapter summarizes beautifully the essence of this book.
18. Love how Dr. Susskind goes over the most prominent physicists of the day and their contributions, including the younger generation. His admiration for Gerard `t Hooft is palpable.
19. An excellent epilogue.
20. A helpful glossary.

Negatives:
1. How scientific is modern cosmology? String theories? A lot of it has that sci-fi feel to it, no matter how hard Dr. Susskind tries to sell it as scientific.
2. Let's face it, there are some topics in physics and cosmology that are truly "far out" and are bound to be over your head. Branes will challenge your brain.
3. Very few endnotes.
4. It requires an investment of your time.
5. No formal bibliography.

In summary, despite some of the challenging topics I really enjoyed this book. Dr. Susskind did a very good job of introducing basic principles and concepts while not shortchanging the public on many of the perplexing challenges that physicists/cosmologists face to describe how the world came to be. The book captures the on-going debates in the physics community and describes quite well where the scientists stand. My biggest concern has to do with how well the theory really captures reality. How sound is the science? That aside, and while some topics are bound to go over your head with curiosity and perseverance it will ultimately educate and satisfy. I recommend it!

Further recommendations: "Hidden In Plain Sight: The simple link between relativity and quantum mechanics" by Andrew Thomas, "Farewell to Reality: How Modern Physics Has Betrayed the Search for Scientific Truth" by Jim Baggott, "Spectrums" by David Blatner, "The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory" and "The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos" by Brian Greene, "A Universe from Nothing: Why There Is Something Rather than Nothing" by Lawrence M. Krauss, "About Time: Cosmology and Culture at the Twilight of the Big Bang" by Adam Frank, "Higgs Discovery" and "Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions" by Lisa Randall, "The Grand Design" by Stephen Hawking, "The Quantum Universe: (And Why Anything That Can Happen, Does)" by Brian Cox, "The Blind Spot" by William Byers, and "The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us" and "God and the Atom" by Victor Stenger.

[Stefano · Rating 3 out of 5]

Mi sono trovato un po' spiazzato - mea culpa - per il cotenuto.
Mi aspettavo un saggio più incentrato su una cosmologia divulgativa, invece è fortemente incentrato su quelle basi della fisica che hanno portato ai più recenti sviluppi teorici (teoria delle stringhe, teoria M, universo-bolla), con particolare attenzione alle particelle fondamentali (elettroni, quark, bosoni, fotoni e compagnia bella).
Dico divulgativo, ma in realtà è abbastanza specifico. Non si addentra in digressioni matematiche con l'utilizzo di formule incomprensibili per i profani, ma nei suoi ragionamenti dà per scontati dei concetti che (credo) per la stragrande maggioranza dei lettori non professionisti siano oscuri. Allo stesso modo, sorvola rapidamente sulle sue spiegazioni visuali di problemi fisici, come se il lettore medio riuscisse a immaginare del tutto agevolmente una 3-sfera che si dilata all'infinito, oppure una brana della teoria M che si avvolge lungo l'asse y toccando l'infinito sulle altre dimensioni, o ancora una stringa a 9 dimensioni. Tutto questo porta, in moltissime situazioni, a non comprendere affatto le concluioni tratte su alcuni dei punti fondamentali delle discussioni.
Non mi sento di consigliare questo saggio a chi sia semplicemente curioso o a chi voglia avvicinarsi alle più recenti evoluzioni della fisica e della cosmologia, lasciandolo invece a chi abbia una infarinatura un minimo solida in fisica delle particelle.

[Michael Huang · Rating 5 out of 5]

Fine-tuning in cosmology refers to the apparent problem that many of the physical constants appear fine-tuned in that even if they change a little bit, some serious consequences follow. Maybe galaxies won’t form. Perhaps chemistry can’t start. In short, we won’t be here. There were many books on the “fine-tuning” of the universe. Some explains the issues (e.g., Just six numbers). Others offer up explanations (e.g., A fortunate universe) that included theism or simulation. Scientists (e.g., Sean Carrol in Big Picture) would tell you why immediate embracement of theism (a common reaction) does exactly nothing to help explain it. Yet others tell you why the notion of fine-tuning is blown out of proportion to begin with (e.g., The fallacy of fine-tuning). Susskind’s book took the issue in a full frontal manner and tried to convince you why anthropic principle should be dropped.

But let’s start with a criticism first. To be honest, the biggest problem with the book is that the anthropic principle (AP for short) is not clearly defined — or at least the nuances should have been exposed early on. On page 7, this is how AP is introduced: “a hypothetical principle that says that the world is fine-tuned so that we can be here to observe it”. This is in fact very vague. If we emphasize the intentionality (the “so that” part), one can interpret this to be God/author-of the-simulation-in-which-we-find-ourselves left this as a subtle clue to his/her existence. But AP could also stand for a completely different interpretation: say our current, fine-tuned universe is highly unlikely and the universe is much more likely to be in a different state with physical constants that can’t support (intelligent) life; then we won’t be there to see it. This is just a long way of answering the fine-tuning observation with “so what”.

To recap, the 1st AP interpretation is just wrong — you’re welcome to believe anything you want, just don’t use fine-tuning to “prove” it. The 2nd AP interpretation is unsatisfying. It’s a non-answer. This book provides a legit alternative to AP. The answer is not simple — cosmologists haven’t yet converged on all details, but it’s quite convincingly presented. First of all, really just one physical constant is genuinely fine-tuned. That is the cosmological constant (made famous by Einstein). Vacuum energy is another name. And the popular press is more likely to use “dark energy”. And it *is* fine-tuned. It’s not quite 0 in our universe, but it has 119 zeros following the decimal point. But a straightforward mechanism can explain why it’s so peculiar. The gist is that string theory may be the answer. If the theory is right, a universe can pop out of “quantum fluctuation” and, depending on its specific configuration, can have any one of roughly 10^500 configurations. Most of these universes are out there beyond our current ability to detect. Heck even our little “pocket universe” is way bigger than what we can see (the visible universe). So the true totality of all that is out there should be called a megaverse, multiverse, or something like that. Susskind calls it the cosmic landscape. Perhaps 10^120 of these configurations can support life. We just happen to be in one of them.

Is the answer right? Well we don’t know. And it’s possible we may never know. However, back in the 1850s, evolution by random mutation and natural selection does not even exist. Even after Darwin’s book, it was ridiculed. But today some 160 years later, our scientific understanding of it is on much firmer ground. 160 years from now, it’s conceivable that this string theory based cosmic landscape hypothesis is either confirmed or falsified. Unfortunately we are probably not around to learn about it. But Susskind’s book is a pretty good exposition of the hypothesis.

[Micah Johnson · Rating 4 out of 5]

This book is about one of the most shocking ideas in modern physics. Susskind's argument goes a little something like this: There are certain measurable physical constants in the universe that we inhabit that can be quantified. These constants represent things like how strongly particles are attracted to one another or how far an electron is from the nucleus of an atom. Lately, some physicists have come to the conclusion that if even one of these numbers was even minutely different, then life and therefore intelligent life could never have existed at all. Furthermore, these values are so very exactly known and within such small tolerances that they seem to have been "tweaked" by some outside agency. Yikes. Now we veer into religion.

To me, this seems like some really awesome ammunition for the intelligent design crew. (Remember, you can't spell "IDiot" without "ID.") Obviously, the tweaker in this case would be the Intelligent Designer and there are some high level physicists who posit this exact scenario. Not so, says Susskind, who then goes on to describe our universe as just one out of an unimaginably large number of universes, maybe even as high as 10 to the 500th power, and out of that many, it stands to reason that there would be a universe exactly like ours which we just happen to inhabit. And though these other universes exist, there's no way to ever observe them or prove it. Make sense? I know I'm probably screwing up the details, but for me, I just can't get past his idea that there really might be something un-knowable about the universe or the multiverse for that matter, should it turn out to exist. It turns my core beliefs into the same kind of superstitions and dogma that I have tried to avoid. I give it four stars because I'm still thinking about it, even months after I read it. Incredible ideas, sad conclusion.

[-uht! · Rating 5 out of 5]

We've got 'The Rare Earth' and now we've got 'The Rare Universe.' This book details Leonard Susskind's theory that our universe one of 2-500X (2 to the 500th power) possible universes. He goes through some of the current theories on how 'pocket universes' form and exactly what would be possible in order for those universes to support life. 'The Cosmic Landscape' is his coined term for the multiverse, or the higher-dimensional space within which our universe was created and for the 'landscape' of possibilities for universes in general. There's some great discussion about why 3 extended space dimensions is conducive for life and probably the best explanation about the Planck length/time I've ever heard (changing the units leading to one of the greatest quantum insights ever). Brilliant shit. But the most interesting part of the book (for me) was the anthropic principle. I'd read about the weak/strong anthropic principle before but always viewed it as a copout. But Susskind is so passionate that 'this universe is exactly how it is because we are here to contemplate it' that he really has won me over. Yes, we still need to figure out why and how, but ultimately life was able to form because this rare universe did what it did. This got me thinking about epistemology and the problem of 'the external world.' In a sense, we each create the entire universe anew every day and when we die, that particular universe is gone. Think about it.

[David · Rating 3 out of 5]

In this book noted physicist Leonard Susskind presents an emerging paradigm of cosmology based on modern string theory. This cosmology addresses the difficult question of why our universe appears to be so specially constructed. For instance, the "cosmological constant" of the universe appears to be the sum of two terms, which cancel to 120 decimal digits, yet fail to cancel in the 120th digit! What can be the explanation for such phenomena? Susskind then discusses developments in modern string theory, which (by his own admission) has miserably failed to provide a simple crisp explanation of our modern world. To the contrary, string theory suggests that there are 10^500 possible universes. Susskind then suggests that maybe this failure is the way out of the paradox. Perhaps our universe appears so extraordinarily well designed is merely an instance of the "anthropic principle" in action -- sure, we are a one-in-10^120 chance; but in an ensemble of 10^500 universes, hey it is bound to happen at least once.

It should be noted that other physicists are dead-set opposed to this line of thinking, which they regard as a complete surrender of the quest for a crisp falsifiable theory. See for instance Smolin's "The Trouble with Physics".

[Stefano · Rating 4 out of 5]

Mi era già capitato di leggere qualcosa sul paesaggio, sugli universi-bolla inflativi e sulla rivalutazione del principio antropico. Devo ammettere che resto piuttosto scettico a riguardo e, anche se Susskind ce la mette tutta per dimostrare la validità di queste teorie, rimane sempre il dubbio che sia solo il tentativo di salvare trent'anni di lavoro sulla teoria delle stringhe. La scoperta dell'esistenza di una piccola costante cosmologica positiva, ha messo seriamente in crisi gli stringhisti. Dalla speranza di trovare una teoria unica si è passati rapidamente ad un proliferare di innumerevoli teorie differenti (il paesaggio). E tutto per far rientrare in qualche modo nel modello i risultati degli ultimi dieci anni di cosmologia sperimentale. E' francamente difficile non pensare ad una forzatura, a maggior ragione se ciò che ne risulta è una teoria così intrinsecamente poco predittiva.
Ciò non toglie che il libro sia avvincente, davvero ben scritto e intriso di quella passione per la ricerca che già avevo apprezzato in "La guerra dei buchi neri".

[Diego · Rating 5 out of 5]

Leonard Susskind uno de los padres de la teoría de las cuerdas y uno de los físicos más prominentes de la actualidad presenta su visión de la evolución del universo. Susskind hace un recuento de los pilares de la física moderna, la mecánica cuántica y la teoría de la relatividad general para luego tratar de explicar como la teoría de cuerdas busca reconciliar estos dos lados de la física.

Desde los diagramas de Feynman, la QED que este demostró y la QCD de Gell-Mann así como la culminación del modelo estándar por parte de Steven Weinberg, Susskind trata de explicar su idea de un paisaje ( un espacio de posibilidades) para explicar porque el universo es como es y como es apto para la vida.

Susskind trata de encontrar una forma de explicar el llamado principio antropico partiendo solo de 3 ideas, la mecánica cuántica, la relatividad general y la ley de los grandes números.

[Lisa · Rating 3 out of 5]

An interesting read, with some excellent explanations of physics. My quibble is how heavily the author leans on a flavor of the Anthropic Principle which seems to put the cart before the horse. In this Panglossian paradigm, the universe has been 'fine-tuned' for our benefit. It seems to me that reverses the logical cause and effect- since we have evolved in this universe, obviously the physical constants and laws must permit our existence. We are fine-tuned to our universe, not vice versa. The author ultimately concludes that there is a 'Landscape of possibilities, populated by a megaverse of actualities', and that like Laplace his hypothesis does not require a god, but that seems rather at odds with his prior explanations of the anthropic principle.

[Bria · Rating 4 out of 5]

Four years of physics curriculum, and I understand more about it after two chapters of this book. Nobody actually takes the time to sit down and explain everything to you. They just throw out equations and words and concepts and bark at you to move it! Susskind actually tells you how it all fits together.

Oh yeah, and then there's all those other universes.

[Paweł · Rating 5 out of 5]

Absolutnie najlepsza książka naukowa, jaką czytałem :D Polecam wszystkim!

[Raymond Lam · Rating 4 out of 5]

Suskind's accessible, lucid, and lively science writing rivals Hawking. When he is recounting stories of meeting colleagues at universities or conferences, his writing is as engaging as a novelist's writing. This book on a String Theory take on the Anthropic  principle is not only useful and needed, but is very enjoying to read due to Suskind's prose.

Suskind offers in the beginning a very clear explanation of the Feynman diagram to be used as a tool for explaining particle physics. He also provides a brilliant account of the significance of the cosmological constant to the fine tuning of the universe. If the constant were negative, galaxies and stars would collapse leading to a collapse of the universe. If it is an order of magnitude greater than the 123 decimal places of the value for this universe,  the repulsive force would prevent the forming of galaxies and star systems.

Suskind uses the notion of "landscape" to set up his treatment of the fine tuning problem.  Landscape is the idea of the variation of the environments of the universe. Each environment has its own constants, laws of physics, and particles based on the fields it has. For instance, if the Higgs field is different, the mass of the elementary  particles and the laws of physics would be different. Variation of fields would offer a diversity of multidimensional landscape in the universe or the "megaverse". The universe features a variation of environments of different vacuum energies. Some of them can be like ours while many aren't. This richness of the landscape variation is how Suskind sets up the problem.

To introduce String Theory, Suskind recounted the interesting story of how he got started on String Theory. He was looking at Veneziano's S Matrix equation on Hadrons collision that Hector Rubenstein introduced to him. He was not at all interested in the particle physics surrounding S matrix  but found the equation oddly looked like about harmonic oscillator. Later he saw that the equation depicts two open end strings colliding with the ends featuring a quark and anti-quark. He called the string "rubber band" because of elasticity. So String Theory started out as a theory about hadrons. Initially there are the baryons string configurations with three strings joined at one end while a quark is on the other end. There is also the simpler meson configuration with a quark and anti quark on each end of the string. When a string replaces a particle in a Feynman diagram and traces out a time elapsed history, a sheet resembling a cylinder results which is called a "world sheet". That is the origin of how the interesting Calabi Yau manifold geometry evolves into many shapes and configurations. String Theory connects with and utilizes General Relatvity's compactification of space to account for how extra dimensions can be compactified. For instance, the cylindrical world sheet seen in a very small scale would appear like a line thereby compactifying 2 dimensions to 1 dimension. Further, using Kaluza-Klein theory of extra dimensions of space being rolled up, String Theory adds 6 more rolled up dimensions to make up 9 dimensions plus time to be the 10th dimension. The distance around a compactified surface is called the compactification scale, which fixes the charge and mass of the particles. In other words, the scale of the surface would vary the laws of physics. Recall that the quantised vibration features of the strings determine the kinds of particles there are.

In 1995, Witten introduced a M theory that modified the String Theory into a version that utilizes membranes instead of string. Membranes are the sheets version of strings. A string in a one dimensional space which is just a 1-brane. The 10 space directions of M theory feature 9-branes.  As indicated above, there are 6 dimensions rolled up in the initial 3 spatial dimensions in String theory. The variations of the Calabi Yau manifolds that can result from the branes offer 10 to the 500 environments or vacuums for String Theory.  The landscape offering these environments are the possibilities that megaverse can take shape literally. How do these possibilities get actualised into pockets of multiverses to constitute the megaverse? It is by  metastability of the vacuums and space cloning which use eternal inflation as the driving mechanism.  Metastability refers to the idea that properties of vacuums that can spontaneously changed into pockets of actual miniverse populating the landscape each of which with a unique own cosmological constant. Space cloning is the replicating of empty space by a bubbling process filling the gap. This cloning process grows exponentially through an inflation process that eventually actualises pockets of miniverse. With pockets of miniverses each with different cosmological constant which produces its own laws of physics and particles, the finetuning of the anthropic principle is easily explained. In a cosmic landscape of possibilities populated by a megaverse of actualities, one of the actualities or miniverses would have the proper cosmological constant and associating law of physics like our observable universe that has the galaxies, stars, and planets to sustain life. It is in effect disarming the notion of fine tuning. Among all the pocket universes,  at least one of them would work. Suskind thinks String Theory is powerful to address the anthropic principle because it has the wealth of numerous Calabi Yau manifolds to offer the millions of vacuum possibilities to be populated into pocket miniverses, thereby showing fine tuning is no more than an actual pocket miniverse among many that has the right working condition.  Suskind did an excellent and lucid job in elaborating this approach.

[Boris Bereček · Rating 4 out of 5]

This book is definitely worth reading. The ideas presented in the book really open up the views to the reader, whether they are right or wrong (I'm not competent to comment on that).

[Last Ranger · Rating 5 out of 5]

Mapping the Void:

This book is endlessly fascinating, frequently frustrating and is, hands down, one of the most difficult books I've ever read. The only reason I was able to get through it at all was Leonard Susskind's ability to clearly communicate complex ideas to the layman reader. Nonetheless, "The Cosmic Landscape" was a real chore to read. String Theory has been around, in one form or another, since the 1960s and has evolved into the many different forms we see today. Like Quark Theory, Quantum Mechanics and some other branches of Theoretical Physics, String Theory is purely a mathematical construct. No one has ever observed an actual "String" or, for that matter, a "Quark" either. But both theories are alive and well, and the subject of ongoing research, to this very day. In "The Cosmic Landscape" Susskind gives the reader a kind of "primer" on these difficult subjects and traces their research history as well. Along the way Susskind introduces several unfamiliar concepts: Condensed Matter Physics, the S (or scattering) Matrix, reading and understanding Exchange Diagrams. The way that Susskind writes is very low key but it's also like taking a corse in Theoretical Physics and listening to Professor Susskind give one of his lectures. Mixed in with the hard science are references to other scientists and their theories, thoughts on his colleagues and past interaction with them. His colorful analogies help the reader to visualize some very abstract concepts. Is he partial to his own thoughts and theories? Of course he is, that's why he wrote the book in the first place. It's up to the reader to take it to the next level and consult other writers for any, possibly alternative, conclusions. Susskind closes his book with a chapter on Summing Up and an Epilogue in which he does some speculating on the future of Theoretical Physics, String Theory and various odds and ends. He also talks about some of his fellow scientists and their thoughts, pro and con, on the theories in this book. The Kindle edition does not include any bibliography for other works in this field though the author does recommend a couple of book in his Notes. There is no cross reference index so you're kinda on your own for any book search. All in all this was a very challenging book but it was well worth my time and it provided me with lots of food for thought, I highly recommend it. While I had no downloading problems with the Kindle edition I did notice a problem with the "chapter notes" that the reader should be aware of. Normally, when there's a chapter note to be read, it's indicated by a number in the text that you click on and the system takes you to that particular note. In this edition, however, when you click on, say, #5 the system will take you to #6. At that point all you have to do is back page to the correct note. Still, the editors should have done a quality-control review before publishing the e-book. No biggie, but just saying.

Last Ranger

[Mark · Rating 4 out of 5]

In this book, theoretical physicist Leanard Susskind, considered to be the father of string theory, discusses various topics such as the Anthropic Principle, string theory, the cosmological constant problem, the string theory landscape, and the holographic principle in ways that can be understood by the general public by using helpful analogies with Darwinian theory, supercooled water, and even the crystalline structure of "ice-nine" from Kurt Vonnegut's sci-fi novel "Cat's Cradle" (!), etc.

Early chapters in the book deal with topics such as quantum electrodynamics, Feynman diagrams and quantum chromodynamics. Then, the cosmological constant problem is introduced, and Susskind explains how the concept of of the string theory landscape / the multiverse and a certain formulation/version of the Anthropic Principle can solve the cosmological constant problem.
I've used ChatGPT 4.x to explain further and in more detail some of the themes, concepts and topics covered in this book and to put everything together:

Vacuum energy is the energy that remains in empty space due to quantum fluctuations, even when no particles are present. In quantum field theory, the vacuum is not truly empty but is instead filled with virtual particles that spontaneously pop in and out of existence. The energy associated with these fluctuations is called vacuum energy, and it is thought to have a significant role in cosmology.

-Gravitational Effects of Vacuum Energy:
Vacuum energy exerts a pressure and has a gravitational effect because, according to Einstein's theory of General Relativity, energy and mass contribute to the curvature of spacetime. However, in everyday contexts, the gravitational effect of vacuum energy is extremely small and undetectable. On cosmological scales, though, vacuum energy is believed to be responsible for the accelerated expansion of the universe. This is often modeled as a form of dark energy.

- Relationship to the Cosmological Constant:
The cosmological constant (denoted as Λ) is a term that Einstein originally introduced in his equations of General Relativity to allow for a static universe. After the discovery that the universe is expanding, Λ was thought to be unnecessary. However, in the late 20th century, observations of distant supernovae suggested that the expansion of the universe is accelerating. Vacuum energy is a potential source of this acceleration, and the cosmological constant is now interpreted as a measure of the energy density of empty space, closely linked to vacuum energy.

As described earlier, vacuum energy is the energy associated with the quantum fluctuations of empty space. When physicists attempt to calculate the value of the vacuum energy density using quantum field theory, the result is extremely large, on the order of 10^120 times larger than the value implied by astronomical observations of the accelerated expansion of the universe. This calculation leads to a huge discrepancy between theory and observation, which is the essence of the cosmological constant problem.

- Vacuum Energy and the String Theory Landscape:
In string theory, the vacuum energy can take on different values depending on how space is compactified—this is part of the so-called string theory landscape. There are potentially a vast number of vacuum states (sometimes referred to as "vacua"), each corresponding to a different possible configuration of space and energy. This large diversity of possible vacuum states provides different values for vacuum energy in different universes.

One potential explanation for the cosmological constant problem comes from string theory and the idea of the string theory landscape. As mentioned earlier, string theory suggests that there are many possible vacuum states, each with different values for vacuum energy. The vast number of possible vacua in the landscape could, in principle, produce a wide range of values for the cosmological constant, including the small value we observe in our universe.

However, string theory does not yet provide a concrete mechanism for why our universe should have the particular vacuum energy it does, making this an unsolved aspect of the problem.

-Anthropic Principle:
The anthropic principle comes into play when considering why the vacuum energy in our universe has the value that it does. If the vacuum energy were significantly larger, the universe would have expanded too rapidly for galaxies, stars, and planets to form. Conversely, if it were much smaller, gravitational forces might have caused the universe to collapse. The anthropic principle suggests that the observed value of the vacuum energy is one that allows for the existence of life (or observers), because in universes where vacuum energy takes on other values, observers could not exist.

This anthropic reasoning is sometimes used to explain why we observe such a small vacuum energy in a vast multiverse, where many different vacuum energies could exist in other universes.

The anthropic principle offers one way of addressing the cosmological constant problem. In the context of a multiverse with many different possible values for the cosmological constant, we might expect that only universes with a small enough cosmological constant would allow for the formation of galaxies, stars, planets, and ultimately life. According to the anthropic principle, the reason we observe such a small value for the cosmological constant is because we live in a universe where conditions are favorable for life to exist.

In other words, in universes with very large cosmological constants, space would expand so quickly that galaxies and stars could not form, and observers like us would never exist to measure the cosmological constant. This reasoning, while controversial, provides a possible explanation for why the vacuum energy is so much smaller than predicted by quantum field theory.

-Summary of Connections:

Vacuum Energy: Quantum fluctuations in empty space.

Gravitational Effects: Contributes to the expansion of the universe, acting as dark energy.

Cosmological Constant (Λ): The energy density of empty space, linked to vacuum energy.

String Theory Landscape: A multiverse of possible vacuum energies corresponding to different configurations of space.

Anthropic Principle: Suggests that our universe has a vacuum energy compatible with the existence of life, explaining its observed value.

-Summary of the Cosmological Constant Problem:

Vacuum Energy: Theoretically predicted value is extraordinarily large due to quantum fluctuations, implying a much stronger gravitational effect than observed.

Cosmological Constant: Observational evidence (based on the expansion of the universe) suggests a much smaller value than predicted.

String Theory Landscape: Suggests that different possible universes with different values of vacuum energy may exist, offering a framework to explore the problem.

Anthropic Principle: Proposes that we observe a small value for the cosmological constant because only such values allow for the existence of life.

In essence, the cosmological constant problem is a clash between quantum theory and cosmological observation, where the small observed value of vacuum energy (via the cosmological constant) challenges our understanding of the universe at the most fundamental level. Despite many proposed solutions, the problem remains one of the deepest mysteries in modern theoretical physics.

Putting all of this together with the holographic principle, Susskind describes the Cosmic Microwave Background map as a "scrambled hologram of an infinity of pocket universes..."

[Brett · Rating 3 out of 5]

This book contains interesting theories of origin concerning the universe as a whole, as well as the various quantum particles the universe is understood to be comprised of. This book gives its theories free of the God-of-the-gaps explanation that: "God made it so", which I agree is completely sensible and expected in a real science book, since science deals with matters of the physical world and only its most necessary constituents, not matters of faith or philosophy.

The book contains many profound facts on elementary particles and fundamental forces, and it is an interesting read on these points alone, however the "the Illusion of Intelligent Design" part of the title should have never been published as part of the title as there is ZERO argument against intelligence or its uncanny ability TO design, that doesn't surpass the sophistication of: "it appears designed, but it really isn't" unless you believe the mere existence of particles and equations to be sufficient evidence to reject intelligence, in which case, in my humble opinion such a claim backfires because it takes intelligence to even make sense of 'particles and equations' in the first place...I was so waiting for this "illusion" to be revealed, and it never happened.

I'm sure having that as part of the title helped sell more copies though...

The fact is, there is no force, either guided or unguided that can create the level of sophistication that we see 'intelligence' doing every day in all manner of disciplines and creative ways. Until one comes along, I'll be a major skeptic of those who belittle it's scope and capability.

A person can decry the validity of intelligence to CREATE something you'd PREFER to be blindly natural, but that hardly stands as any more compelling proof than accepting the opposite based on inferring from what we know intelligence is already capable of. In my opinion such a rejection of common experience offers far LESS proof.

[Yael · Rating 5 out of 5]

THE COSMIC LANDSCAPE tells the intriguing story of the gradual acceptance by physicists of the implications of certain weird aspects of quantum mechanics, implications that entail an infinite multiverse or megaverse comprising endless populations of universes of every conceivable form and variety. Here, too, is the story of the battle between the proponents of Intelligent Design, who draw on quantum mechanics to try to show that our universe is uniquely fashioned for life and intelligence, and scientists who believe that our universe arose as a result of natural processes, its hospitability to life and intelligence a product of scientifically comprehensible phenomena. When Susskind was a student, he was laughed at by his scientific idols for his ideas -- ideas which are now the solid stuff of physics. Over the last century, physical science has growth from Newtonian mechanics to Einsteinian relativity to a quantum-mechanical wonderland, a process that Susskind details beautifully in this fascinating book. For newcomers to quantum mechanics, it's slow going at first, but Susskind's patient, step-by-step discussion of basic concepts is understandable to any intelligent reader, and soon the novice has enough of the new concepts under his belt such that the reading begins to go faster and faster. By the end, one is whizzing through the brave new multiverse the author has introduced to us, delighting in every parsec of it. I got my copy through the Science Fiction Book Club; that's how accessible it is even to laymen. I loved it.

[James F · Rating 3 out of 5]

Leonard Susskind is the co-discoverer of string theory, and has many other physics accomplishments to his credit. Unfortunately, being a good popular writer does not seem to be one of them. This book is somewhat rambling and repetitive; it does not explain string theory as understandably to the layman as Brian Greene, or the Anthropic Principle as well as Lee Smolin. There was very little new in this book that I hadn't read before. To be fair, though, the book was not intended simply as a popularization of physics, but as a discussion of how the concept of the Landscape affects the meaning of the Anthropic Principle as a philosophical concept -- how it answers the problem of "the illusion of intelligent design." On the positive side, the book was very straightforward and focused on the science -- none of the "gosh-wow" that turns me off to some popularizers -- and it was interesting to see how a leader in the field interprets some of the ideas that I have read about by other authors. The final chapter deals with his dispute with Steve Hawking on Black Holes and information; I will be reading his book on that subject next.

[Drchak · Rating 3 out of 5]

String theory has a multitude of solutions resulting in many possible universes each with its version of physics - the "cosmic landscape" is the solution space of all possible universes. Some are friendly to life and many others that do not. What is special about our universe? A potential answer relies on the anthropic principle that has gone out of fashion a few hundred years ago. Susskind and others incl Weinberg have embraced this - meaning our universe is one of many. From a layman's perspective I can believe this given what seems to be the evidence. But as with quantum theory this notion seems very alien to us.

Interesting perspective on how the universe is not "elegant" with a mish mash of particles, forces, dark matter, dark energy etc. Sometimes the book touches on a few tantalizing subjects and moves on - I was left scratching my head on quite a few topics. The penalty of being a layperson i guess!

[Ushan · Rating 2 out of 5]

Both the fundamental constants of nature (the mass of an up or down quark divided by the mass of an electron, the fine structure constant etc.) and the initial conditions of the Universe at the time of the Big Bang seem very fine-tuned for our existence; if they had been even slightly different, organized matter would not exist. Susskind says that perhaps there are many universes, each with its own constants, but only those where the constants are close to ours have beings like ourselves. I don't get it. If the fine structure constant is different in different universes, it must have been drawn from some probability distribution, which we cannot estimate because we only have one sample. So instead of one number for which we don't know where it came from we have many numbers, the moments of the distribution. Are these numbers the true constants of nature, or are they themselves drawn from some distributions? Is it turtles all the way down?

[David Hammond · Rating 4 out of 5]

This book is a wonderful review of 20th and 21st century physics. Susskind does an amazing job of explaining things so that a layman such as myself can understand them, or at least get a better sense of what truly understanding them would mean. Although I know that I will forget many of the finer points in short order, I at least feel that I now have a better grasp of many of the major advances in physics from the last century.

Susskind spends a great deal of time and energy in this book defending the anthropic principle, and I found these parts of the book the least interesting. Perhaps I am not embroiled enough in the debate to totally get the point of it. As he explains it, the anthropic principle is a framework for explaining and exploring the properties of our universe. It is not, I don't think, the only framework for doing so. Oh, well, that's not for us laymen to argue about.