Roger Penrose refutes his critics: defending the singularity theorem

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Roger Penrose won the Nobel Prize for showing black holes are real and General Relativity predicts the existence of a singularity at their center. But recently, another black hole pioneer, Roy Kerr, claimed there was a mistake in Penrose's proof. This was hyped widely across the media by the likes of Sabine Hoseenfelder, PBS Spacetime, Anton Petrov, and Ethan Siegel. Sabine Hossenfelder especially praises Kerr's work.
However, leading relativists say Kerr makes simple errors, and his conclusion is totally unfounded. Here, we talk to these experts and explain how science popularisers got their physics so badly wrong. Nobody claims that singularities are real, but the singularity theories are powerful signposts to new physics, probably requiring a quantum theory of gravity to resolve.
A timeline of the video is here:
00:00 introduction
01:20 Need for quantum gravity
02:20 geodesic
5:00 types of geodesics
5:35 types of time
6:20 affine parameter
8:16 Kerr's argument
10:37 Highly misleading
12:28 Finding Kerr's core error
15:18 PBs space-time
17:50 The mistake of the Popularisers
20:40 We are not idiots
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Wow. That was a real beat down. I love this. Well done everyone. 👏👏

MISTERASMODEUS
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Very brave to show massive physics channels getting it wrong. May you not be affected by any backlash from the fans. I really appreciate your willingness to get into the weeds and explain what the disagreement is.

Cat_Woods
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Penrose has an extremely profound mind and everything he says must be deeply analyzed and understood before criticizing it, before he's usually correct.

ekekonoise
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From a 72. Year old searcher of how everything is connected thank you the public needs sources like this.

bobdobs
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I followed Sir Roger Penrose and I finally just rested on only numbers. During my journey. Yes! He is so absolutely timeless

brendawilliams
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Sir Roger Penrose is amazing in so many regards but what defy imagination is his simple way of speaking about complicated subjects and make them clear. I hope to be as alert as he is when I'll get his age.
Thanks for this video, great and interesting subject 🤗 as Always 🤩

kevinbarbe
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Let me be the first to say any self-respecting cosmology student should actually watch this from start to finish. This channel rocks!!

BenMargiotta
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The term "affine" is used in many areas, including computer science, mathematics, and machine learning. It has interesting definitions in each field.

picksalot
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Haven't finished watching the video, but I will say that I appreciate that a video like this, with a critical look at Kerr's paper, has come out. At first, I was hyped up when I first saw Kerr's paper (admittedly part of the reason is that I am desperate for a breakthrough in theoretical physics 😬), but reading it I was quite unimpressed, and left confused at what Kerr wrote that either hadn't already been addressed long ago (when the definition of a "singularity" in GR was established in the 60s, and is well explained in the Hawking & Ellis book from 1973), or that simply didn't address what Penrose's theorem actually says. But anyway, I hoped there was more to Kerr's paper than I got the impression of, considering that we were talking about, well, Roy Kerr, after all. For that reason, I was happy when I saw that the paper was finally mentioned by popular science media. But after having thought about it more and reading from the perspective from other theoretical physicists, confirming part of my suspicion and also clearing up exactly what the null geodesics that Kerr considered corresponded to in the Kerr spacetime, I came to the conclusion, that, indeed, the paper was hollow and based on a misunderstanding. So now I've come around to say I'm glad to finally see popular science media that present a critical look at his paper!

Edit: Great job interviewing relevant physicists on the area, especially Penrose himself!

frede
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I'm currently reviewing 2 books I've had since their release, Shadows of the Mind & The Emperor's New Mind by Professor, Sir Roger Penrose, for a thread I'll write soon as I've spent most of my life studying mathematical physics as an amateur (studied O level in both). I'm a big fan of Roger Penrose because I like his original thinking & visual spatial methods of communication so have a timeless quality. Regards Claire

clairecsmith
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Thanks to great physicists, explaining with examples, I could finally grasp the meaning of affine parameter of null geodesic that has been in news recently!

Mukulindo
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Great contribution this video is.
Also, I might add that it is trivial to prove that an affine parameter is always a linear function of proper time (not coordinate time, but proper time). So if one is bounded so is the other.
One can imagine their relationship as this: We can use a rotated line (affine parameter: applicable to light too) to index points on the original line (proper time: which for light is unusable); The reason we use the rotated line is that the original line had a bad/difficult/unusable direction (the so-called light-like direction);



Sorry Prof. Kerr

itsawonderfullife
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Awesome episode again. This channel should be more popular than Sabine or PBS. And hey! There's footage of skydiving in it, finally!

hiroki
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Sir Roger Penrose arguably the most accomplished person on the planet! Thank you Sir Roger for your brilliant mind!

jozincarnate
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I have been waiting for this subject to get covered by someone since the Kerr paper came out. THANK YOU

johnburke
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In this world there are only three certainties: Einstein, Penronse and death.

LuisAldamiz
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Good stuff indeed! It is amazing that we can hear these discussions from the authors themselves. Thanks for birnging them to us!

vin
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Nothing & Everything:

Several hypothesis and theories propose that at some point in time, all matter and mass in the universe will be swallowed by black holes, then all of the information about the matter is evaporated as hawking radiation and becomes photons. Roger Penrose has a very strong hypothesis called Conformal Cyclic Cosmology that I highly recommend studying.

In this scenario, spacetime ceases to exist because photons do not experience time or space. In the absence of spacetime, all photons become a single, unified photon capable of exceeding the speed of light through quantum tunneling and entanglement. This leads to an infinite overlap of all points in the universe, creating a paradox where the universe simultaneously ends and begins. The exact moment everything becomes a photon is the exact moment everything becomes matter again, demonstrating a paradox where GR and QM overlap, and the universe exists in a state of both physical and non-physical infinity.


This is an extreme scenario where all matter in the universe converts to photons, resulting in a universe composed entirely of massless, virtual particles. Given that photons travel at the speed of light and do not experience time or space. This conversion of matter into energy leads to the cessation of spacetime. Due to quantum tunneling, entanglement, and the absence of spacetime constraints, all photons unify into a single photon capable of exceeding the speed of light, leading to the simultaneous end and rebirth of spacetime. This is where E=mc², and m=E/c² come into play. c² is the square of the speed of light, which only happens when there is no vacuum.

1. What we know about Photons
   - Photons are massless particles that always travel at the speed of light. According to special relativity, photons do not experience time or space; there is no interval between their point of emission and absorption in their frame of reference. If the universe becomes a unified photon, spacetime, as traditionally understood, ceases to exist.
   - The cessation of spacetime means that the conventional dimensions of time and space lose their meaning because there is no mass to curve spacetime, and photons themselves do not require spacetime to exist in the conventional sense.

2. The Singularity Illusion
   - In a photon-only universe, without the usual constraints of spacetime, all photons can be considered as part of a single, unified quantum state. This unified state implies that all photons are entangled with each other, sharing the same quantum properties and existing as a singular entity, resulting in a super position.
   - Quantum entanglement allows for instantaneous correlations between particles regardless of distance. In the absence of spacetime, the distance and time separation between entangled photons becomes meaningless, allowing them to behave as a single, unified photon.

3. c²
   - With spacetime ceasing to exist, the unified photon state is not constrained by the speed of light limit. In a spacetime-less state, photons can "tunnel" across the entirety of what would be considered the universe without restriction. This process is known as quantum tunneling.
   - This unified photon state also allows quantum entanglement to exist simultaneously across all points, effectively exceeding the speed of light. The photon’s wave function would encompass the entire universe instantaneously, creating a state where all spatial and temporal coordinates overlap, and the moment the wave function collapses is the moment the physical universe is created.

4. Endless cycle of Birth, Death, & Rebirth
   - In this state where all photons are unified and spacetime has ceased, photons can interact through quantum fluctuations and collisions, leading to pair production. This process would spontaneously generate particle-antiparticle pairs (such as electrons and positrons), reintroducing mass into the universe.
   - The moment mass is reintroduced, spacetime is reinstated. The paradox arises because the exact moment spacetime ceases is also the moment it begins again. The absence of spacetime allows the unified photon to exceed conventional limits, while its interactions simultaneously recreate matter, restoring spacetime. Time is the measurement of matter as it moves in space.

In a universe where all matter converts into photons, the cessation of spacetime allows for the formation of a single, unified photon state. This state enables photons to exceed the speed of light through quantum tunneling and entanglement, resulting in an infinite overlap of all points and moments in the universe. The universe reaches a paradoxical state where its end and rebirth occur simultaneously. The instant spacetime ceases due to the lack of mass, the unified photons vibratory rate exceeds the speed of light leading to the immediate re-emergence of matter and spacetime.

At the exact moment when everything becomes photons and spacetime ceases, photons unify and exceed the speed of light, creating a state of infinite simultaneity where the end of the universe overlaps with its beginning. The universe’s fabric collapses into a singular quantum state, where the cessation of spacetime is indistinguishable from its rebirth through pair production. This unified state of everything is consciousness.

- Physics falls apart

This hypothesis challenges the traditional limits of physics, suggesting that without spacetime, the universe can transcend its normal physical laws. The super position state of the unified photon, enabled by quantum entanglement and tunneling, allows for behavior beyond conventional speed limits and dimensional constraints.

- The Paradox
The unified photon state’s ability to exceed the speed of light in the absence of spacetime leads to a condition where all events and locations are superimposed. The instantaneous reintroduction of matter via pair production ensures that the universe does not remain in this state. Instead, it transitions back to a state with spacetime, creating a loop where the cessation and existence of spacetime are one and the same.

- Paradox
The cessation of spacetime, combined with the unified photon state’s super position behavior and quantum properties, creates a paradoxical infinity where the universe’s physical and non-physical states coexist. The concept of time does not pass between these two states, creating a moment that is both an end and a beginning, a state of infinite simultaneity and unified existence.

OfTheVoid
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I remain puzzled. The problem for me is the statement that light experiences no Affine Time. The obvious example is the red shift caused by the expansion of space through which it moves. Though I would also wonder about the change that occurs during its creation and as it interacts with some mass.

richardderekadams
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I would love if you did a video on the EP equals epr paper by maldacena and the difference in looking at an object from the outside or from observing it from within. Also how the complexity inside of a black hole can increase at a rapid pace. Which is one of the reasons they say you cannot Traverse a wormhole. Personally I always thought when an electron and positron come into being there is some sort of Wormhole between them which apparently is something they're studying.

Epoch