- Physical Review D - Remembering Stephen Hawking ()
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- Remembering Stephen Hawking (1942-2018)
- The Black Hole Wars: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics

The world is made up of physical A good introduction to the debate in physics regarding on whether information was lost when it entered a black hole. The world is made up of physical objects on which "information" can be coded by means of differing physical configurations of said physical objects. But it is the physical objects, it seems to me, that are the primary ones and about whom physics can be done. It may be mathematically and conceptually easier to think of these physical configurations as containing "information", but said "information" cannot exist apart from the physical objects in their respective configurations.

Thus, it is not "information" which gets or doesn't get lost when it enters a black hole, but rather an ensemble of physical particles in particular configurations. The book also mentions the holographic duality principle: wherein all the physical happenings on a particular chunk of space can be coded on any surface which surrounds said chunk of space.

Using this principle, the author claims that the universe is a hologram, with the real physics going on at the boundary of space-time. But this claim goes too far, I think. Just because we can recover some of the physical information about solid objects from shadows on a wall does not mean that the shadows are more real or have primacy over the solid 3-dimentional objects. Why do physicists want to make this jump and state that the real physics is happening at the boundary while the things going on inside the volume are as incorporeal as a hologram? Why is it not the other way around? Mildly interesting book, if you can ignore those two confusions.

Could the King of physics be wrong about black holes? For 30 years Hawking and Susskind debated whether or not information disappears once it is sucked into a black hole. I commend Susskind for his courage not in debating Hawking, but in explaining concepts like Quantum Mechanics, Quantum Gravity, and String Theory to regular people like me. If you want to learn more about your universe and you don't want to spend a lot of time on the math - this is the book. These black hole ideas are important Could the King of physics be wrong about black holes?

These black hole ideas are important because if Hawking is right and information really does disappear once the black hole evaporates then we too disappear - erased forever! One day we will all be at the horizon of a black hole and eventually at the singularity - and sucked in!

Susskind proves his own argument theoretically using Gerardus 'et Hoofts "holographic principle" and Hawking is forced to make a statement that gives Susskind victory once Suskind proves the math. This book is a twisty, unexpected, real-life story about real people who set physics on a new path.

## Physical Review D - Remembering Stephen Hawking ()

You'll learn physics terms and a lot about influential people who changed the way we see the world today. Jul 16, Isk rated it really liked it. Started a year ago, finally finished! Hate Susskind's writing -- shut the fuck up with your inane and bloated "war" metaphor that appears every other page.

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And no, you don't need to constantly remind that why you were always so sure you were right and that you couldn't believe all the other physicists were too dense to see why the war was important. But the cool physics is inside. Hawking: seemed to prove that information is irretrievably lost in a black hole.

Also, empty space full of super-flee Started a year ago, finally finished! Also, empty space full of super-fleeting black holes that pop in and out of existence almost instantaneously and these quickies do erase info. Susskind: WTF!

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Einstein's equivalence principle: You can't distinguish between accelerating e. So, e. Pollywog dumb hole-illustration of black holes: Doppler effect. The pollywog falling into the sinkhole does fall, but the pollywog watching the doomedee sees the doomedee taking an infinite amount of time to reach the horizon. Minkowski space and proper time: the proper time between two events along a worldline in Minkowski space is the amount of time passed according to a stopwatch that travels along that worldline.

According to this proper time metric, a straight worldline between two events has the largest proper time! Quantum jitters: put a bunch of particles in a super-tiny box, and then cool the box down to absolute zero. Classically, you'd think that this means the particles have velocity zero, but by the Uncertainty Principle, these particles are jittering! Black holes can be thought of as regions of maximally compressed information.

Bekenstein showed that adding one unit of entropy to a black hole by sending a photon whose wavelength is equal to the radius of the horizon -- this ensures that all we know is that the photon is somewhere in the black hole, not where increases the mass of the black hole such that the surface area of the horizon increases by one square Planck unit.

So the entropy of a black hole in bits is proportional to the surface area of its horizon in Planck units. But note that the horizon is supposed to be indistinguishable to someone passing through -- this disparity is fundamental to the BHW. It used to be thought that black holes of any fixed size were indistinguishable from one another. But Hawking showed that black holes have a temperature, and thus, that they must radiate electromagnetic radiation i.

Two kinds of jitters: quantum jitters and thermal jitters the latter are due to excess energy.

Thermal jitters are due to real photons that bombard our skin and transfer energy to it; quantum jitters are due to virtual photon pairs which are created and then quickly disappear. One member of a virtual photon pair may be inside the horizon, while the other may be outside -- but someone outside the horizon can't see the photon trapped inside. So what someone near the horizon detects as quantum jitters will look like thermal jitters to someone outside the horizon.

From Hawking's formula for the temperature of a black hole, temperature is inversely related to mass, so that smaller black holes are hotter and larger black holes are colder. But if black holes evaporate, what happens to the information that gets sucked into them? Hawking says that this information disappears.

## Remembering Stephen Hawking (1942-2018)

But to Susskind, this violates the law of information conservation, which he thinks is always satisfied. Einstein's Principle of Relativity: physics is the same in all reference frames moving with uniform velocity relative to each other. But how can you make this compatible with Maxwell's Principle that the speed of light is constant? Also, Einstein's Equivalence Principle: the effects of gravity and acceleration are indistinguishable. What happens to someone falling into a black hole? By quantum mechanics and quantum jitters , an observer sees the poor dude evaporating as he crosses the horizon since particles near the horizon must be super energetic, since after all they're escaping from a black hole!

## The Black Hole Wars: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics

By relativity and the Equivalence Principle, the person falling into the black hole survives until hitting the singularity. Which is right? Complementarity, as in the complementary particle-wave nature of photons. If a photon is trapped inside a box say, by making the sides of the box mirrors , then as the box gets smaller, the photon's wavelength must also get smaller since the photon's wavelength can't be larger than the sides of the box. This means that the energy in the box increases, so its max increases.

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So smaller is heavier. Holographic principle. There is a 2-dimensional scrambled representation of our 3-dimensional world for out on the boundaries or beyond of our universe. Take any spherical region of space. The maximum amount of entropy this region of space can contain is given by the entropy of a black hole, which is proportional to the surface area of the black hole's horizon. How to tell whether a particle is elementary or not? One way: see if you can spin it. If so, then it's not elementary. String theory: there are two applications.

One is 'large-scale'.

Mesons are two quarks connected by a string made of gluons. Quarks can come in six flavors up, down, strange, charmed, bottom, top and three colors red, blue, green. Gluons have a positive and negative pole, and each pole has a color red, blue, green. Glueballs are closed string-gluons without quarks.