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The Nobel Prize in Physics 2020

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Re: The Nobel Prize in Physics 2020

#141

Post by pbhjpbhj »

mongol wrote: post #105
melling wrote: post #74

Earlier quoted context omitted.

He has also written a few books. https://www.amazon.com/Roger-Penrose/e/B000AQ045A%3Fref=dbs_...

Has anyone read his writings on consciousness? When I was young and still believed in free will I imagined that consciousness used quantum mechanics as a way to generate free will. I later learned that Penrose had theories that sounded similar. But have not read about it.

IIRC be wrote about that in The Emperor's New Mind a formative book for me (even though I was still at highschool when I read it) but one I haven't really returned to now I've a more academic understanding of the subject matter. To-do!

Re: The Nobel Prize in Physics 2020

#142

Post by pbhjpbhj »

dnautics wrote: post #91
wenc wrote: post #64

Earlier quoted context omitted.

I somehow always had the impression that Roger Penrose was a numerical computation guy (Moore-Penrose pseudoinverse). I did not realize he had this vast of scope of a contributions in physics. Certainly quite impressive.

penrose tilings is a contributions to pure mathematics, too

Veritasium YouTube channel has a good video on Penrose tiles that my kids just watched, https://youtu.be/48sCx-wBs34 .

Re: The Nobel Prize in Physics 2020

#143

Post by centimeter »

sharpneli wrote: post #117
centimeter wrote: post #104

Earlier quoted context omitted.

I have heard of space becoming timelike, but have never heard of time becoming spacelike in a black hole. Do you have more information on that?

PBS Space Time is pretty decent and understandable source if one doesn’t want to wade trough the maths. I heavily recommend the whole black holes playlist. https://www.youtube.com/playlist?list=PLsPUh22kYmNBl4h0i4mI5...

I do want to wade through the maths, and I have to some degree, and I've never come across time becoming spacelike (which would imply rotation past the null vector, which afaik is not something that happens in a black hole).

Re: The Nobel Prize in Physics 2020

#144

Post by a1369209993 »

pbhjpbhj wrote: post #96
pa7x1 wrote: post #46

Earlier quoted context omitted.

The radial direction of the inside of the Schwarzschild Black Hole is timelike. This means that; inside the event horizon, the inevitable passage of time becomes the inevitable move towards the singularity at the center of the Black Hole. To answer your question in clear terms: No, you cannot move freely in the radial direction. Only towards the center, in the same way you cannot move freely forward or backwards in t…

Considering a point particle, what constrains it from orbiting [which is what I'm assuming we're meaning here as all matter has to move radially to cross the event horizon]? If it had a tangential component to its momentum prior to meeting the event horizon (EH) wouldn't it continue to orbit past the EH?

> what constrains it from orbiting

Not quite what you seem to be asking, but the event horizon is the point where[0] the escape velocity is equal to the speed of light; the orbital velocity at that distance is greater (by a factor of ln 2 IIRC, so v_orbital ≈ 1.44c). There's a more distant distance, called the innermost stable orbit or the photon sphere, where the orbital velocity is equal to c (so photons will orbit if you emit them tangentially at this height), but the escape velocity is only ~0.69c.

0: It's not quite right to say that that's because the escape velocity is equal to c, though.

Re: The Nobel Prize in Physics 2020

#145

Post by a1369209993 »

Isinlor wrote: post #90
kryptiskt wrote: post #41

Earlier quoted context omitted.

Not necessarily, a supermassive black hole can have quite bearable gravity at the event horizon (as the event horizon radius depends linearly on the mass and the gravity declines quadratically with distance). You still wouldn't be able to communicate your experiences though.

What is supposed to happen with different types of chemical bonds? If half of a molecule is inside a black hole and half is outside, the half inside is necessarily constrained to the black hole, while a molecule outside does not have such constraint. The chemical bonds should be also necessarily broken at least for a moment, since an atom inside black hole can not exert electromagnetic effects on an atom outside blac…

> If half of a molecule is inside a black hole and half is outside,

You know how the universe is expanding, such that the milky way is moving away from (sufficiently) distant galaxies faster than the speed of light? But chemistry still works fine here? When you fall into a black hole, you accelerate until you're moving away from the rest of the universe faster than light, but all your atoms are still (relatively, assuming the black hole is large enough to have negligible tidal forces) stationary relative to each other. The event horizon is just the point where your speed relative to the effectively-distant[0] outside universe exceeds the speed of light. Any signal you emit can't be moving facter than c relative to you, so it will always be moving away from the outside universe (v0: "Nothing can move facter than c" refers to relative motion of objects near each other, which is why the Hubble expansion of the universe doesn't contradict that either.

Re: The Nobel Prize in Physics 2020

#146

Post by a1369209993 »

pbhjpbhj wrote: post #140
pas wrote: post #76

Earlier quoted context omitted.

Yes, it could, and yes, it theoretically [in some models] contains/radiates information. But the "radiation" happens right at the event horizon, the particles that get emerge have been "created" on the outer side. https://www.youtube.com/watch?v=XT_iZ7QEit8

This seems as good a place as any to ask: when the particle-antiparticle pairs are made at the event horizon, one falls in, the other is emitted as radiation. Why don't the p & ap produced then pair up with and annihilate with other ap and p created in the vicinity such that it wouldn't really be detectable over ordinary vacuum activity. This could happen both inside and outside the horizon. It seems like Hawking rad…

The particle []or[] antiparticle (only one avoids falling in) produced usually does pair up and annihilate with another (anti)particle, but that happens above the event horizon, so the photon resulting from that annihilation sometimes is pointed away from black hole and escapes. It's only very small black holes where the pair-production particles themselves have sufficient height and speed to escape.

Re: The Nobel Prize in Physics 2020

#147

Post by pas »

pbhjpbhj wrote: post #140
pas wrote: post #76

Earlier quoted context omitted.

Yes, it could, and yes, it theoretically [in some models] contains/radiates information. But the "radiation" happens right at the event horizon, the particles that get emerge have been "created" on the outer side. https://www.youtube.com/watch?v=XT_iZ7QEit8

This seems as good a place as any to ask: when the particle-antiparticle pairs are made at the event horizon, one falls in, the other is emitted as radiation. Why don't the p & ap produced then pair up with and annihilate with other ap and p created in the vicinity such that it wouldn't really be detectable over ordinary vacuum activity. This could happen both inside and outside the horizon. It seems like Hawking rad…

Good question, but I have no idea, and ... it's ... complicated. Basically don't think about it in that way, because the math uses QM and frequencies.

https://math.ucr.edu/home/baez/physics/Relativity/BlackHoles...

http://www.scholarpedia.org/article/Hawking_radiation#The_or...

Re: The Nobel Prize in Physics 2020

#148

Post by tegeek »

simiones wrote: post #94
tegeek wrote: post #39

What is more poetic than a mathematical model of a black hole? Look at this A "finished" black hole (The end state of the gravitational collapse) doesn't have a volume or any density. This is the mathematical solution first obtained by Schwarzschild in 1916. So standard mathematical solutions of the black holes are vacuum solutions. There is "nothingness" inside the event horizon. The outside observer would see a col…

You shouldn't forget that, since the mathematical equations have a singularity at the center of a black hole, we can be reasonably sure that they are in fact incomplete and can't accurately describe the internal structure of a black hole. So, take any such description with a grain of salt. It's much more correct to say that our current models can't accurately predict what is happening past the event horizon of a blac…

First there is nothing called center of a blackhole. What mathematics tells us is exactly what is a black hole. After crossing the event horizon, there is no time so there is no "information" exists. Its the end of "everything" which I wrote "nothingness". Thats what is in the black hole. Thats the structure.

Re: The Nobel Prize in Physics 2020

#149

Post by thisrod »

animationwill wrote: post #58

> Roger Penrose used ingenious mathematical methods in his proof that black holes are a direct consequence of Albert Einstein’s general theory of relativity. Where can I learn more about these ingenious math models in a way that an adult can understand, but one that's been out of math for a while? Is there a good YouTube video? I'm searching but it's coming up with many hour-long lectures by Roger Penrose that seem u…

> an adult can understand, but one that's been out of math for a while?

That might not be possible. I remember struggling with the proofs of the singularity theorems, in the last year of my physics degree, after two semesters of differential geometry. Some of the things that people win the Nobel Prize for are genuinely hard.

The Large Scale Structure of Space-Time is the classic. However, it's the book that Hawking was referring to in his joke about every equation halving the sales.

Re: The Nobel Prize in Physics 2020

#150

Post by gizmo686 »

tegeek wrote: post #148
simiones wrote: post #94

Earlier quoted context omitted.

You shouldn't forget that, since the mathematical equations have a singularity at the center of a black hole, we can be reasonably sure that they are in fact incomplete and can't accurately describe the internal structure of a black hole. So, take any such description with a grain of salt. It's much more correct to say that our current models can't accurately predict what is happening past the event horizon of a blac…

First there is nothing called center of a blackhole. What mathematics tells us is exactly what is a black hole. After crossing the event horizon, there is no time so there is no "information" exists. Its the end of "everything" which I wrote "nothingness". Thats what is in the black hole. Thats the structure.

There is very much time after crossing the event. It happens to not correspond to the "t" coordinate that a distant observer would call time, but it still exists.

The mathematics describes 2 singularities with black holes. 1 singularity occurs when describing the black hole using the coordinate system of an observer at constant distance. This is a coordinate singularity and goes away under an appropriate change of coordinates.

Another singularity occurs at what the constant distance observer would describe as the "center" of the black hole. This is not a coordinate singularity. The curvature there goes infinite regardless of your coordinate system.

Whether or not you want to call this singularity the "center" is a matter of opinion. An observer within the event horizon would describe the singularity as a time, not a location, so "center" certainly has some connotations that you may want to avoid. On the other hand. In the coordinate system that I normally see used to describe the interior of black holes, the singularity occurs at the surface r=0; which sounds kind of center-ish.

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