**spoiler alert** I enjoyed this book and read it in only a few days.
It disappointed me in a couple of places, however. In the "Battle of Santa Barbar**spoiler alert** I enjoyed this book and read it in only a few days.
It disappointed me in a couple of places, however. In the "Battle of Santa Barbara" Susskind introduces the Black Hole Complementarity Theory. Part of the theory uses the Equivalence Principle to describe what would happen to someone who falls throught the Horizon. "Obviously, at least one of the endings must be wrong since they say opposite things. Nevertheless, I have come to tell you the impossible: Neither story is false. They are bothe true -- in complementary ways."
The Equivalence Principle is simply not absolutely true. (Note 1) It can be a good approximation for some calculations. But measurement of tidal forces (or gravitational gradient) within any frame of reference will identify whether the frame of reference is an accelerating frame far away from gravity sources or whether it is in a strong gravitational field. Even the difference between a free-falling frame of reference and a frame in a distant orbit can be determined because the falling one has a much higher time-rate-of-change of the gravitational gradient than the orbital one. So "Equivalence" in my mind is a "flat-earth" approximatation, quite useful in block-size civil engineering, but unacceptable when building the Channel Tunnel. (See Asimov's "The Relativity of Wrong."
I expected some discussion from Susskind about how Equivalence isn't strictly true, but it is still good enough at the Horizon. But he seemed to treat Equivalence as a rock solid principle that will not be invalidated near a black hole. Maybe it won't, but some discussion is needed.
Another weak spot in his story was what does "Steve" observe of the Black Hole and its horizon and environments as he approaches and falls throught it. He is undergoing time dialation before falling in, and he would have to report some of those affects if he were reprieved at the last moment.
And what was completely missing is what does "Dave" (my invention) see who is sentenced only to orbit the Black Hole eliptically and pass very close to the Horizon and return to report his observations.
The book made me think.
Note 1: (From Wikipedia:Equivalence Principle: So the original equivalence principle, as described by Einstein, concluded that free-fall and inertial motion were physically equivalent. This form of the equivalence principle can be stated as follows. An observer in a windowless room cannot distinguish between being on the surface of the Earth, and being in a spaceship in deep space accelerating at 1g. This is not strictly true, because massive bodies give rise to tidal effects (caused by variations in the strength and direction of the gravitational field) which are absent from an accelerating spaceship in deep space.
**spoiler alert** I consider this one of the best, most though provoking books, I've ever read.
It brings together an eclectic mix of concepts from Ast**spoiler alert** I consider this one of the best, most though provoking books, I've ever read.
It brings together an eclectic mix of concepts from Astronomy, Geology, Paleontology, Climatology, Genetics, and Evolotionary Biology.
The thesis is simple: That life in the Universe is probably more common that we though 20 years ago, but that intelligent life is probably much more rare than we thought.
He doesn't offer proof, but he presents several independent concepts why the process of evolution created intelligent life needs some "luck".
One case in point. The MOON is important/essential? for the development of intelligence on Earth. The MOON??? Our Moon is an "outrigger" on the rotation of the earth, stabilizing its axis to point more or less in a narrow range of angles with respect to the sun for a couple of billion years. This allows for stability of climate. Without a moon, for some significant portions of Earth's history the axis would be a much higher angles of incidence, causing large portions of the earth to be in daylight or night for months at a time. Having most portions of the earth experiencing cycles of Antartic and Saharan conditions every year would not be conducive to the development of intelligence. Yet the moon, a comparitively large body in relation to the body it orbits, is itself a very unlikely development. We have learned how the moon could have been formed, but it requires collisions of bodies early in the solar system's development of just the right size, at just the right speed and angle of impact, that it would make an odd's maker in Las Vegas blanch.
**spoiler alert** I just recounted to my 16 year old three stories from this book, then went and fetched it from my bookshelf. I read it in 1985. The**spoiler alert** I just recounted to my 16 year old three stories from this book, then went and fetched it from my bookshelf. I read it in 1985. The three stories were:
RF as the supervisor of the "computer room" at Los Alamos. "These army privates would rather be fighting overseas. Let me tell these soldiers what they are doing and why its important." Soon the soldiers were running the place better than he could.
RF's first visit to the Y-12 Plant. Sees test vats of UF6 without concern for avoiding arrangements that would cause critical mass." RF: "Aren't your afraid the real stuff will explode?" "Explode?!?!" No one had told them what they were doing other than processing a chemical.
RF's second visit to the Y-12 Plant: Blueprints everywhere. Safeguards builtin everywhere. No criticality possible anywhere. But its all coming way to fast. RF does not understand the blueprints. Is that square thing a valve or a window? It's way to late to ask now. Points to a square on the diagram (hoping to find out what it is), "What happens if that valve is closed?" 30 seconds of bable, then "Oops! We'll fix it and get back to you."
**spoiler alert** This was one of those bargain-shelf treasures you find now and then. It is a more or less chronological account of the discovery and**spoiler alert** This was one of those bargain-shelf treasures you find now and then. It is a more or less chronological account of the discovery and study of the first naked eye supernova in 383 years.
What I particularly remember from the book is the passage of what someone orbiting such a star would see. In short: nothing... First, the only planets to have survived the star's earlier Red Giant stage would have to be at Neptune's orbit or beyond. Secondly, the neutrino flux from the colapsing core is a couple of hours ahead of the surface breakout of the extream ultra-violet flash. In those hours, the neutrino flux would be so dense that it would cause a beta-decay radiation dose in the magnitude of 10,000 rads. Human beings receiving such a dose are "incompacitated immediately and die within a week." pg 234....more