I’m a great fan a popular science books, particularly when the topic is cosmology or fundamental physics. Susskind’s “The Cosmic Landscape” was particularly enjoyable, though I will take issue with a few things in later posts. For now, here are a few highlights:
I love a good illustration:
A rocket-propelled lemon moving away from you might have the color of an orange or even a tomato if it were going fast enough. While its moving toward you, you might mistake it for a lime.
This is simply the Doppler effect, which we’ve all observed for sound as an ambulance drives past. It works for light as well, but you have to be going close to the speed of light. Using the right formula from Einstein’s special relativity, we find that you must fire a lemon at a tenth of the speed of light to make it look red. About the same speed, but moving toward you, will make it look green.
Susskind gives an excellent account of the fine-tuning of the universe for intelligent life.
[T]he Laws of Physics may not only be variable but are almost always deadly. In a sense the laws of nature are like East Coast weather: tremendously variable, almost always awful, but on rare occasions, perfectly lovely. … One theme has threaded its way through our long and winding tour from Feynman diagrams to bubbling universes: our own universe is an extraordinary place that appears to be fantastically well designed for our own existence. This specialness is not something that we can attribute to lucky accidents, which is far too unlikely. The apparent coincidences cry out for an explanation.
In particular, he takes the discussion to the cutting edge of particle physics, discussing the gauge hierarchy problem:
Physicists puzzled for some time about why the top-quark is so heavy, but recently we have come to understand that it’s not the top-quark that is abnormal: it’s the up- and down-quarks that are absurdly light. The fact that they are roughly twenty thousand times lighter than particles like the Z-boson and the W-boson is what needs an explanation. The Standard Model has not provided one. Thus, we can ask what the world would be like is the up- and down-quarks were much heavier than they are. Once again – disaster!
… the cosmological constant problem:
Throughout the years many people, including some of the illustrious names in physics, have tried to explain why the cosmological constant is small or zero. The overwhelming consensus is that these attempts have not been successful.
… fine-tuning of cosmic inflation needed to give the universe the right amount of lumpiness:
A lumpiness of about 10^-5 is essential for life to get a start. But is it easy to arrange this amount of density contrast? The answer is most decidedly no! The various parameters governing the inflating universe must be chosen with great care in order to get the desired result.
… and even supersymmetry:
The biggest threat to life in an exactly supersymmetric universe [has to do] with chemistry. In a supersymmetric universe every fermion has a boson partner with exactly the same mass, and therein lies the trouble. The culprits are the supersymmetric partners of the electron and the photon. These two particles, called the selectron (ugh!) and the photino, conspire to destroy all ordinary atoms. … in a supersymmetric world, an outer electron can emit a photino and turn into a selectron. … That’s a big problem: the selectron, being a boson, is not blocked (by the Pauli exclusion principle) from dropping down to lower energy orbits near the nucleus. … Goodbye to the chemical properties of carbon – and every other molecule needed by life.
Susskind is also clear to distinguish between the landscape of string theory and a multiverse (or megaverse):
The two concepts – Landscape and megaverse [a.k.a. multiverse] – should not be confused. The Landscape is not a real place. Think of it as a list of all the possible designs of hypothetical universes. Each valley represents one such design. … The megaverse, by contrast, is quite real. The pocket universes that fill it are actual existing places, not hypothetical possibilities.
All in all, the Susskind’s book is highly recommended.
Letters to Nature 
Luke, I can endorse your recommendation, at least as far as readability is concerned. I read this book several years ago and, even though I am a total layperson in cosmology, I found it fascinating and easy to understand.
I look forward to your comments on where you disagree with him.
A question regarding fine tuning.
Compare if you will the idea of getting life the equivalent of drawing a particular set of cards from a deck. Evidently, you need a particular combination to get life – namely, heavy elements and other circumstances.
The odds of getting that combo approach zero. Oh well.
My question is, so what ? Surely, if the laws were different, there would be other phenomena instead of life which we do not have now. An entire universe of anti-matter, maybe.
Why do we fixate on getting this improbability when so many others were missed out ? Isn’t that just life being important to us simply because we happen to live and those things don’t ? What makes you think we’re special, and our intelligence or replication somehow makes us more special than the countless things that might have been ?
Second question. Assume if you will that the universe is fine-tuned via actual design, and not a multiverse scenario. Would the specificity of the information of those constants in bits in the mind of the creator be not exactly equal to the reciprocal of the probability of generating the combination of the constants in the right values by sheer chance ? How is this an improvement ?
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