String theory's rival: alive & well, YouTubers wrong again. #physics #universe

PBS Space Time, Fermi Lab, and other YouTube physics channels have all said we can test Strng's theory's main rival, Loop Quantum Gravity, by looking for a deviation from something called Lorentz Invaraincne. But what is Lorentz Invariance, and does Loop Quantum Gravity predict this?
Do new measurements rule the theory out, as Biran Keating claimed in a new video? Watch here to find out the truth, not the hype.
If you want to see what loop theorists say about the theory, watch our documentary starring Carlo Rovelli, Abhay Ashtekar, Lee Smolin, Francesca Vidotto, and Aurelien Barrau. They discuss the history of loop quantum gravity and what it means for big questions like what's inside a black hole and what happened before the Big Bang?
A timeline of this film is below
00:00 Introduction, Penrose and the singularity
00:15 Biran Keating's claims re loop quantum gravity and string theory
00:39 PBS Space-time claims
00:52 Fermilab claims
1:10 Carlo Rovelli refutes the Yotubers
A link to Brian's video is here:
A link to PBS Spacetime here
and to Fermi labs video here:

[DrBrianKeating]

Thanks, Phil. But expecting your audience to watch a documentary about angular momentum peculiarities from Carlo from five years ago is inefficient and wholly unrealistic.

Also, while I have a very popular YouTube channel, I am primarily the Chancellor’s Distinguished Professor of Physics at UC San Diego, an experimental astrophysicist with 30 years of experience, a fellow of the American Physical Society, the PI of the Simons Observatory, and author of 200 peer-reviewed publications and two US Patents. I’m not just some “popularizer”.

More importantly, had you thoroughly studied the video and references, you’d see that the leader of the LHAASO paper himself (i.e., certainly not a popularizer) is also convinced the result is correct with respect to its implications for disproving some models of LQG.

Lastly, I have hosted Carlo many times and proposed ways to improve LQG via experimental tests. He’s agreed to come back on The INTO THE IMPOSSIBLE Podcast to discuss my video — which you could have linked to - and the current situation with respect to LHAASO. Thanks

[louisnemzer]

Leonard: Sorry Leslie, I guess I prefer my space stringy not loopy.

Leslie: Well, I'm glad I found out the truth about you before this went any further.

[adreaminxy]

Keating’s dream in his own words: being the Joe Rogan of physics youtube

[tdsdave]

Was going to post this (keating account )to you, very fast response on your part, nice one .

[KirkKellnWasHere]

Hi Phil. Big B jumped the gun. Certain interpretations on whether or not LQG is sunk by these findings depends on how spacetime is understood. Loop Gravity Theory does not actually predict any change in the speed of light if spacetime is properly understood.

To understand this claim, I’ll introduce you to a Grand Unified Theory (GUT) that integrates elements of Loop Quantum Gravity (LQG) with a framework that emphasizes the role of consciousness in shaping our experience of the universe. This theory builds on foundational principles from physics but adds a critical layer: the interaction between the physical world and the world of forms, mediated by consciousness.

Let me explain this theory step by step, and I’ll make the strongest possible case for why it offers a compelling explanation for the nature of reality.

1. Spacetime as an Emergent Property
We begin by shifting our understanding of spacetime. In standard quantum gravity theories like LQG, spacetime is treated as a quantized, discrete structure at the Planck scale. This leads to predictions, such as possible variations in the speed of light for high-energy photons, because they would interact with the discrete fabric of spacetime.

However, this GUT suggests that spacetime is not inherently granular. Instead, spacetime emerges as a property that is imposed by consciousness as it navigates the block universe. The block universe is the complete, static structure of reality—a timeless and deterministic universe that contains all possible states of matter, energy, and events. But it is consciousness that generates the experience of time, change, and the perception of a granular spacetime.

Analogy: Think of spacetime like the grid on a video game screen. The game's world exists in its entirety within the game engine, but the grid (the discrete structure of space and time) only emerges as you interact with the game world through the controller. In this analogy, the game engine is like the block universe—complete and static. The grid you see on your screen is the emergent spacetime, shaped by how you interact with the game.

2. Consciousness Imposes Granularity
In the GUT, the granularity of spacetime—the discrete units predicted by Loop Quantum Gravity—is not an inherent feature of the block universe. Rather, this granularity is imposed by consciousness. Consciousness functions like a filter, interpreting the block universe in such a way that spacetime appears discrete to an observer.

This means that spacetime granularity is a product of observation, not a fundamental property of the universe. Therefore, when we observe the universe at high energies (such as when studying photons with wavelengths near the Planck length), it might appear that spacetime becomes "granular" because of how our consciousness interacts with and interprets these extreme scales.

Example: Imagine looking through a microscope at a smooth surface. As you zoom in closer, your interpretation of the surface becomes more detailed, and eventually, it might appear pixelated because of the limitations of the microscope. The surface itself hasn’t changed—what’s changed is the level of detail at which you're observing it. In the GUT, spacetime behaves similarly. As you "zoom in" to higher energies, the granularity you detect is imposed by your observation—not by the physical universe itself.

3. Time and Experience are Generated by Consciousness
Now let’s talk about time. Traditional theories, like string theory and LQG, struggle with how to explain the emergence of time. Time seems to be woven into spacetime, but at the quantum level, time becomes harder to define. In this GUT, time is not a fundamental feature of the universe. Instead, it is generated by consciousness as it moves through the block universe.

The block universe contains all possible events, past, present, and future. However, time is experienced as consciousness "moves" through these fixed events, generating the illusion of change and progression. This explains why, in this theory, we don’t experience a singular, frozen reality but rather a flowing, dynamic world.

Analogy: Think of the block universe like a library containing every possible book. All the stories (events in the universe) are written and completed, but you experience the story only as you read it, moving from page to page. Your consciousness is the reader, generating the sense of time and sequence as it travels through the already-determined structure of the block universe.

4. Consciousness and the World of Forms
In this GUT, there is a distinction between the physical world and the world of forms. The physical world is finite, static, and inherently continuous. The world of forms, by contrast, is infinite and discrete—it represents the abstract principles, laws, and patterns that define the structure of the universe.

The world of forms governs the underlying order of the universe, but it is through consciousness that the experience of time and granularity (spacetime) emerges. The interaction between the physical world and the world of forms is mediated by consciousness, which serves as the bridge between these two domains.

This view contrasts sharply with string theory, which treats spacetime as a background in which vibrating strings exist and create particles. In the GUT, spacetime is an emergent phenomenon created by the conscious interaction with the block universe, not a pre-existing background in which matter and energy operate.

5. Why the Speed of Light Doesn't Change
Given this understanding of spacetime, let’s return to the prediction about the speed of light: In traditional LQG, the speed of light might vary at very high energies because light interacts with the discrete structure of spacetime. However, in the GUT, we now know that the granularity of spacetime is imposed by consciousness, not by the universe itself. Therefore, even as light approaches the Planck scale, it is not actually interacting with any physical limit or discrete structure inherent to spacetime.

The speed of light remains constant, because the granularity that might appear at high energies is a consequence of how we observe and interpret the universe. The block universe itself is smooth and continuous, and the perception of spacetime granularity is an artifact of our consciousness interacting with it at those extreme scales.

Example: Consider the way digital photos appear pixelated when you zoom in too far. The image might seem to have a "limit" in resolution, but that limit is imposed by the camera's sensor, not by the object being photographed. Similarly, in this GUT, the speed of light doesn’t change, because the perception of granularity in spacetime is analogous to the pixels we see in a photo—it’s part of our interpretive framework, not a feature of the physical world itself.

6. Density-Driven Inflation of Spacetime
The GUT also incorporates a model of spacetime inflation called Density-dragged, Limit-induced, Inflationary Model (DLIM). This model suggests that spacetime inflates at different rates depending on the density of mass and energy.

In regions of low density, spacetime inflates faster, while in regions of high density, spacetime inflates more slowly. This inflation is not caused by any external field (as in some string theory models), but rather by the interaction of matter and energy with the emergent spacetime. This provides a rich framework for explaining the large-scale structure of the universe.

Example: Think of spacetime like fabric being stretched. If the fabric is thick in some places (high density), it stretches more slowly, while in thinner places (low density), it stretches faster. This results in a universe that inflates at varying rates, consistent with observations of cosmic inflation, without needing additional fields or extra dimensions as required in string theory.

Furthermore, with the GUT, the faster-than-expected rotation of stars at the edges of super galaxies is explained by the density-dependent inflation of spacetime. In regions of lower density, spacetime inflates faster, providing the necessary boost to the stars’ orbital velocities without requiring the presence of dark matter.

7. The Superiority of the GUT
In summary, the Grand Unified Theory offers a comprehensive explanation for both the physical world and the subjective experience of reality. By placing consciousness at the center of the universe’s interpretation, the GUT avoids many of the conceptual difficulties faced by other theories, such as string theory’s need for extra dimensions or its struggle to explain the emergence of time.

Spacetime is not a fixed, background entity but an emergent property of the interaction between the block universe and consciousness. Time is generated by consciousness as it moves through the block universe, solving the problem of how time emerges in a static universe.
The speed of light remains constant because the granularity of spacetime is imposed by consciousness and doesn’t reflect a physical limitation in the universe. The universe’s inflation is driven by density variations, explained by the emergent nature of spacetime, without the need for extra fields or dimensions.

Conclusion:
The Grand Unified Theory surpasses traditional quantum gravity and string theory models by integrating the role of consciousness into the very fabric of the universe. It explains why we experience spacetime, time, and change while maintaining the deterministic structure of the block universe. This approach offers a unified framework for both the physical laws of the universe and the experiential nature of reality, providing a robust and compelling model for understanding the totality of existence.

[TheMemesofDestruction]

Aren't there different versions of LQG?

[momo]

Can we get Dr. Rovelli to say something about the recent outburst of sensationalized video content?

[nickmhc]

As a complete casual, I think I agree with Brian Keating’s comments… it sounds like all the videos you cited only discussed evidence against loop quantum gravity, which you’re treating as law.

Matt O’Dowd, who I think is heading up the best active YouTube channel on the platform right now, also produced an entire video exploring loop quantum gravity.

[Nightscape_]

Bummer that string theory was a red herring. Still, knowing is half the battle.

[yojihagiya]

in constructing a unified theory, I think that bogus general relativity must be eliminated, or we will never be able to construct a proper theory anytime soon.

[Sciolist]

To be honest I didn't get head or tail of this

[Openskylook]

This youtubers think they have monopoly over popularizing science. They quickly jumped to ridicule lqg. But they dont come up with thier own better idea and theory against string theory

[Mentaculus]

But are you going to refute someone who “lost the Nobel Prize”❗️Besides, even if there was an effect, would it be some function that “asymptotically” approaches a limit as the photon energy approaches the Planck energy? So it seems that the photon energies that would exhibit an effect would have to be much higher than what has been ever been observed. Keating’s response is that the infinitesimal effect gets to “integrate” over billions of light years. So it seems that “somebody’s” math doesn’t conceptually apply.

Also Anton Petrov has a new youtube video that seems to have the conclusion that “the experimental results are just providing a much lower limit on the energy where quantum gravity might start exhibiting certain effects”! AND “is still not a complete violation because in this case the actual signal from this Lorentz invariance violations are expected to be super tiny so maybe this was just not detected because it was just much smaller than what the scientists measured”!

I think a longer explanation is needed. Thank you for the alternative explanation (but I am still not clear what is going on). Carlo Rovelli was literally a bit hand-wavy and you have excellent explanations for the “rest of us”.

[monkerud]

I think its a trivial to resolve issue really, is there a prediction of a difference in propagation speed or not, its simple, does the vacuum behave this way or that way, like an ideal dielectric material with perfect transmission but shifted phases that depends on wavelength or not?

In principle a theory like models of lqg could be in either camp, you have to ask how it deals with light propagation in the vacuum, simple as that. I'm not that familiar with all models of blinking winking lqg, but the basic idea i can imagine going either way, and the reason i belive that to be true is kind of simple, i have constructed many models of light propagation in vacuum, and you can so to speak make the elephants tail wiggle in any way you like to paraphrase von neumann. The question is a question of economic principles, starting wkth the basic idea of quantized spacetime in LQG, what do you have tk modify to go one way or the other, or add on in terms lf complexity, and before having actually done this work myseuvased on LQG only having done a crude review, i think it should be possible to do either without twisting yourself into pretzels.

[zhavlan]

❤New tape measure for measuring the Universe❤. Let's work with the postulates of Einstein's theory of relativity.
And if we apply new technologies for this, using the experience of Michelson Morley on the airplane fixing speed 200, 300, 400 m/s., we will see how quantum gravity works. Such measurements are impossible on the satellite due to weightlessness.

[CosmoPhiloPharmaco]

Whoa! I can't believe these Youtubers (so-called "experts") missed that.

[monkerud]

The assertion that some theory has some prediction, should be evident in references, but when done in a public forum like this, should be explained in detail, even if you can only do it in a video like this using a toy version wkth the same implications flr the purposes of demonstration, its not so useful tk leave it up to the kmagknauof th audience, which might not be able to work it out from the sources provided, whether they are accurately represented in the video or not.

[elliotpolanco]

What is the name of the female voice in the video, i like her videos.

[siqueirabarros]

Good. Not only all these guys talk greek, they also talk wrong. We are all doomed. 🤦

[HarryNicNicholas]

i watch keating for his guests, when he stops moaning about not getting a nobel i might watch him again.