a short reviewhttp://physicsworld.com/cws/article/multimedia/2015/dec/15/book-of-the-year-2015
----Messaggio originale---- Da: John Clark <[email protected]> Data: 23/04/2016 23.54 A: <[email protected]> Ogg: Trespassing On Einstein’s Lawn I just finished Amanda Gefter’s new book, Trespassing On Einstein’s Lawn, physicist Sean Carroll called it “The most charming book ever written about the fundamental nature of reality” and I think he’s right. Gefter is obsessed with answering the question “why is there something rather than nothing?" ; needless to say she hasn't found a definitive answer but I have found 46 points in the book that may have some relevance to the question: 1) A good definition of "nothing" is infinite unbounded homogeneity. 2) A “thing” is defined by it’s boundaries; a blank paper is not a picture until a line is drawn on it. 3) Godel’s Theorem is a good thing because it provides a boundary and without a boundary there is no thing. 4) The boundary of a boundary is zero so everything you need to know about the interior of a thing is on the boundary. 5) Something and nothing are not opposites just different ways of looking at the same thing. 6) A person’s light cone might provide the boundary to turn nothing into something. 7) The Big Bang happened everywhere. 8) Bits are the fundamental building blocks of reality. 9) Paradoxes always crop up when you try to describe physics from a God’s eye view, so such a view can not exist. 10) Spacetime curvature does not require a God’s eye view, it can be measured from within. 11) For electromagnetism you have to expend energy to make a large electrical charge but with gravity it’s the opposite, it wants to make things lumpy so unlike electromagnetism gravity has a negative contribution to total energy in the universe. 12) The universe has zero energy. 13) But zero is too precise a number for Quantum Mechanics because "nothing" is unstable. 14) The vacuum’s virtual field gives quarks 95% of their mass, the Higgs field does the rest. 16) Quantum particles don’t have positions in spacetime only probabilities. 17) Something is ultimately real only if it is invariant. 18) Progress in physics comes from discovering what was thought to be real is actually observer dependent. 19) A inertial observer in free fall sees a straight line through space time. 20) Others see the person accelerating in a gravitational field tracing out more and more space in less time. and thus producing a curved world line. 21) You can turn a curve into a straight line by stretching the paper, gravity stretches spacetime. 22) A curved world line in flat spacetime is exactly the same as a straight world line in curved spacetime. 23) A gauge force fixes the mismatch between observers, gravity is a gauge force as are all the fundamental forces in physics. 24) The local curvature of spacetime cancels out energy and momentum, and that’s why mass curves spacetime. 25) In General Relativity mass (and because E=MC^2 energy too) is only defined within reference frames, it is observer dependent. 26) Entropy is a measure of hidden information, and a event horizon can hide information. 27) Entropy is not conserved. 28) The more symmetric something is the less information it contains. 29) The Entropy of nothing is zero. 30) The very early universe was smooth and symmetrical and thus had low Entropy. 31) Gravity wants to make the universe lumpy and thus increase it’s Entropy. 32) The maximum number of bits of information inside a sphere is equal to one fourth the area of the surface in Planck Areas. 33) A Black Hole contains as much information as any volume can, although its amount is proportional to the Black Hole's surface not its volume. 34) Hawking radiation is observer dependent. 35) A unmeasured bit of quantum information can not be perfectly copied, if you could then you could outsmart the uncertainty principle. 36) Quantum Mechanics says information can’t be destroyed but General Relativity says it can be, the confrontation comes to a head in Black Holes. 37) A outside observer would say information never crosses the Event Horizon of a Black hole but stays on the surface. 38) A observer falling into the Black Hole would say information does cross the Event Horizon without incident and nothing unusual happens until the Singularity is reached. 39) A black hole the mass of our sun, would take about 10^67 years to evaporate by Hawking Radiation. 40) Hawking Radiation contains information on what went into a Black Hole. 41) The time needed to decode Hawking Radiation increases exponentially even with a Quantum Computer. 42) It would take not 10^67 but 10^10^67 years to compute what went into the Black Hole from the Hawking Radiation that came out of it, and the Black Hole would be long gone by then. 43) The location of information is observer dependent, so nobody can see the same quantum bit at 2 different locations at the same time because no observer can see both inside and outside a Black Hole horizon at the same time. 44) If Quantum Mechanics and General Relativity don’t contradict each other that must mean that if you haven’t finished the computation then the information is not there yet. 45)The only thing that's invariant is nothing 46) Reality is observer dependent, and the weirdness in physics doesn’t come from non-locality but from non-reality. 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