co-host of Sending Poets podcast
Montana, USA
Joined April 2022
- Tweets2.2K
- Following886
- Followers257
- Likes3.9K
Bob Davidson retweeted
The holographic principle is one of the alternative ways of understanding the universe we live in. It proposes that the physics inside a region of space can be fully described by degrees of freedom on its boundary, one dimension lower.
The idea starts with black hole entropy. Bekenstein and Hawking showed that a black hole has entropy
S = A / 4ℓₚ²
where A is the area of the event horizon and ℓₚ² = Għ/c³ is the Planck area, about 2.6 × 10⁻⁷⁰ m². The entropy scales with area, not volume. That is unusual. In ordinary quantum field theory, the number of degrees of freedom in a region grows with its volume.
The black hole result turns out to be a universal limit. Suppose a region contains more entropy than a black hole of the same size. Add a little mass and it collapses into a black hole, whose entropy is only A/4ℓₚ². Entropy would then have decreased, violating the second law. So the maximum entropy any region can hold is set by its boundary area. This means the true number of degrees of freedom in nature scales like area. A volume-based description overcounts.
From this, 't Hooft (1993) and Susskind (1995) proposed that a theory of quantum gravity in a region should be equivalent to a theory living on its boundary. In 1997, Maldacena made this precise with the AdS/CFT correspondence: string theory in five-dimensional anti-de Sitter space is exactly equivalent to a four-dimensional quantum field theory without gravity on its boundary. Later, the Ryu–Takayanagi formula showed that the entanglement entropy of a boundary region equals the area of a minimal surface in the bulk, divided by 4G. Bulk geometry is encoded in boundary entanglement.
There are clear limits. AdS/CFT works for negatively curved spacetime, but our universe, dominated by dark energy, is close to de Sitter, with positive curvature. Bousso's covariant entropy bound extends the area law to general spacetimes, but no complete holographic description of our universe exists, and there is no direct experimental test yet.
Still, the core lesson is hard to ignore: the information content of space is limited by area. If that holds, space itself may not be fundamental but may emerge from quantum information on a boundary.
Bob Davidson retweeted
In 1852, Ludwig Schläfli proved that above four dimensions only three regular shapes can exist. The paper sat unpublished for 34 years - too far ahead of its time. Two dimensions have infinitely many regular shapes. Three have five. Four have six. Then the universe hard-codes exactly three forever - and every LLM embedding space and every quantum chip operates in the dimensions where this permanent pattern lives.
The reason five platonic solids exist and not six is pure angle arithmetic. Stack regular polygons around a shared corner - sum below 360 degrees and you get a valid 3D corner, hit exactly 360 and you get a flat tiling, exceed it and the surface warps like a potato chip. Triangles give three valid solids, squares one, pentagons one. In four dimensions the same logic produces six polytopes - including the 600-cell with 600 tetrahedral faces and 1152 symmetries. Above four dimensions only three families survive: the simplex, the hypercube, and the cross-polytope. The hypercube tiles n-dimensional space the way cubes tile 3D - the same structure indexing positions across every transformer attention grid today.
25 minutes. Bookmark & watch today. The sequence 5, 6, 3, 3, 3, 3 and the geometry behind every dimension your model operates in.
Bob Davidson retweeted
Quantum mechanics makes sense, a physicists shows mathematically, if the universe has two dimensions of time, rather than just one. Does this make sense? I've had a look at the paper.
Bob Davidson retweeted
The Holographic Universe
In QIH, what you're seeing is information rendered as reality. Gravity compresses geometry like a zip file. Light measures change, and the brain reconstructs the hologram.
More videos on my Facebook page:
facebook.com/100063489523265
Bob Davidson retweeted
I thought it'd be a good idea to do a quick summary of the points I have made about the problems in the foundations of physics, just to make it more difficult for the offended physicists on X to pretend misunderstanding me:
(A) The problem with the foundations of physics is that physicists continue to use methods that demonstrably do not work. They have made tens of thousands of so-called "predictions" for new particles, forces, extra dimensions etc etc, that were simply wrong. You can check this yourself. The literature is full of this nonsense. It has come to the point where a "prediction" in this field no longer means anything. It's embarrassing. And they're not doing anything about it.
I have NOT said that the problem is that it takes them a long time to make progress. It is true of course, that that theory development in the field has basically stalled since the completion of the standard model. But who is to say whether this is just because the questions are difficult.
If you think I have said that it is taking too long, you are confusing me with someone else.
I have said instead that the problem is that they are using methods that evidently do not work. And that they do not update these methods is hugely worrisome because it demonstrates a failure of science to self-correct. It shows that the self-correction in this community is broken.
(B) I have been very clear with saying that the problem is theory development in the foundations of physics. Not the foundations of physics per se (clearly experiment has made progress), not physics per se (clearly there is more to physics than the foundations), but theory development in the foundations of physics.
(C) In my book Lost in Math, I explain that historically the method that has worked best (for theory development in the foundations) has been requiring mathematical consistency. This is why I argue physicists in these areas should prioritize solving problems of mathematical consistency and/or inconsistency with experiments. Examples: quantum gravity, measurement problem in quantum physics, dark matter. This is not an exhaustive list.
(D) I did not say that mathematical consistency is either sufficient or necessary for a successful new theory. I made a much weaker point, which is that historically it has worked well. Evidence speaks for it.
Obviously just because a theory is mathematically consistent doesn't mean it also correctly describes nature. Meaning: Physicists must also make sure their theory can, and will be tested. If they work on a theory without thinking about how to experimentally test it, that is not scientific.
(E) People who haven't read my book sometimes think I say physicists use too much maths. This could not be farther from the truth. I argue they need to take maths more seriously.
(F) Because of the above, I have repeatedly said that string theory has a good motivation. If you think I am a big critic of string theory, again, you are confusing me with someone else.
(G) I have said that while these issues seem specific to the foundations of physics, they are symptoms of a bigger underlying problem that affects all of academia, which is that scientists get rewarded for producing papers that they themselves call progress. Progress in academia has no tangible external measure, hence they are optimizing irrelevant goals. It's a systemic problem that has been much discussed by sociologists and economists and many, if not most, academics are to some extent aware of it.
In the foundations in particular, physicists have hit on the rather obvious simple fix of producing theories that simply have no relation to the real world and then discussing them forever, claiming that paper production counts as progress in some sense. I'm not having it and neither should you. This nonsense needs to stop.
(H) I have been writing and speaking about this for about 20 years. Indeed it's how I got to know @ericweinstein , because I organized a conference about this a long time ago. The idea that either of us is going on about this because it is somehow "popular" contradicts facts. Rather what has happened is that at last at least the more informed public is paying attention to what we have been pointing out for a long time is a huge problem.
Bob Davidson retweeted
乔布斯曾在一次采访中说：
“我特别喜欢和聪明人交往，因为不用考虑他们的尊严。”
记者就反问：
“聪明人难道就没有尊严吗？”
乔布斯解释说：
“聪明人更关注自己的成长，时刻保持开放的心态，而不是捍卫面子，不是想方设法证明自己没错。”
所以，认知低的人最大的特征就是永远无法理解你的维度。
你说的是逻辑，他听的是情绪；
你讲的是结构，他在想你是不是瞧不起他。
和认知低的人沟通就是一种巨大的消耗，因为你们根本不在同一个频道：
你讲理，他就打感情牌；
你分析因果，他反问你是不是太冷血。
最后你不得不放弃沟通。
你试图唤醒一个没有自省能力的大脑，本身就是徒劳。
认知低的人无法分清楚事实和观点，他们会用自己的情绪和偏见为这个世界下结论。
Bob Davidson retweeted
Three golden rectangles, set mutually perpendicular, quietly define a regular icosahedron. Their twelve corners are exactly its twelve vertices.
Bob Davidson retweeted
Imagine Einstein quietly sketching an alternative to his own gravity theory in the late 1920s—one where spacetime isn’t curved at all, but twisted. Nearly a century later, that forgotten mathematics may explain why the universe’s expansion is speeding up… and why our two best ways of measuring that speed refuse to agree.
In the standard picture, dark energy is a fixed positive push, a cosmological constant that has always been gently stretching space. But new data from DESI and the long-standing Hubble tension (early-universe measurements say 67 km/s/Mpc; nearby supernovae say 73) hint that something more dynamic is going on. Model-independent reconstructions even suggest that, billions of years ago, the effective density of this mysterious component may have been negative—as if the universe once experienced an extra squeeze rather than a push.
Standard general relativity forbids this: negative energy densities tend to spawn “ghosts”—unstable fields that would tear the vacuum apart. So physicists long ignored the possibility. A team led by Özgür Akarsu has now revived Einstein’s teleparallel gravity (flat spacetime with torsion instead of curvature) and explored a long-discarded mathematical branch. In their f(T) model, the effective dark energy density naturally starts negative in the distant past (roughly more than 9.5 billion years ago), crosses zero around redshift z ≈ 1.5, and becomes positive today—driving the acceleration we observe—without ghosts or instabilities.
The twist (literally) is suppressed in dense places like the Solar System by a chameleon-like screening, so local gravity tests still pass. On cosmic scales, however, this sign-flipping behavior offers a fresh way to ease the Hubble tension and match the evolving dark energy suggested by DESI.
A simple change of geometric language—curvature to torsion, and the willingness to follow a negative root—turns a forbidden scenario into a potentially elegant solution.
Source article: iXBT Live
Original paper: Akarsu et al., Phys. Rev. D (arXiv:2410.23068)
Bob Davidson retweeted
“Have no respect whatsoever for authority; forget who said it and instead look what he starts with, where he ends up, and ask yourself, “Is it reasonable?”"
-- Richard Feynman
Bob Davidson retweeted
Opponents of logical positivism like to quote A.J. Ayer’s quip to Bryan Magee that the problem with the philosophical movement is that “nearly all of it was false.” What they typically fail to note is that he immediately adds that it was still “true in spirit”! 1/🧵
Bob Davidson retweeted
“Action depends upon perception, and perception on action.”
The assumption that perception is a window onto reality has the brain backwards, argues Oxford neuroscientist Thomas Parr.
Under the Free Energy Principle, perception and action are the same process: both work to close the gap between what we predict and what we encounter, either by updating our beliefs or by changing the world to fit them.
Curiosity, Parr argues, is as fundamental to behaviour as reward: we act not just to get what we want, but to know our world better.
Tap here to read Parr’s full article. iai.tv/articles/your-brain-d…
Bob Davidson retweeted
Days ago, a breakthrough revealed what 4D actually looks like.
For a century, we treated 4D like sci-fi portals and spinning cube animations. The GIF below looks cool, but it’s mostly a parlor trick.
The real mathematics is far wilder: boundaries do not exist.
In 4D, a sealed bank vault has no roof, and your ribcage has no walls. A 4D observer can touch your heart without scratching your skin.
Bob Davidson retweeted
The brain doesn’t store memories like a hard drive; it functions like a holographic phase conjugator. During a memory formation event, traveling standing waves imprint local electrical potentials and dipole moments across cellular substrates (Levin, 2021). When a retrieval cue sweeps through, it scatters off these pre-patterned micro-fields, generating a "time-reversed" phase-conjugate wave (Pepper, 1982). This wave travels backward, un-scattering distortions to perfectly reconstruct the original neural profile via cavity resonance (Yariv, 1978). Rhythmic timing then gates this reconstituted wave back into conscious working memory (Buzsáki, 2006).
🤖 Made with AI
Bob Davidson retweeted
Pilot-wave theory—also known as de Broglie–Bohm theory—seems to keep resurfacing.
It aligns with everyday intuition: an oscillator is fundamental and generates a pilot wave around itself. Particles, in this view, behave like oscillators. The central idea of string theory is similar, which is presumably why it was named “string”—a reference to the basis of oscillation.
The universe might be likened to a pressure cooker: we may exist within a black hole, or something analogous to one. Immense pressure provides the energy driving these oscillations. Particles must be repulsive; repulsion under pressure produces oscillation, while concentrated oscillations give rise to particle-like behaviour and uncertainty. Where oscillations cluster, they form entities such as a proton or an electron.
🤖 Made with AI
Bob Davidson retweeted
Heinz Hopf discovered this in 1931. Roger Penrose called it "an element of the architecture of our world." Eric Weinstein brought it up on Joe Rogan - and the silence in the studio said everything. Most mathematicians spend entire careers never touching it, yet the structure lives inside the geometry every LLM operates on.
The Hopf fibration maps a 4D hypersphere onto a regular sphere using circles that never intersect but each links through every other exactly once. It shows up in at least 8 areas of physics - including the Bloch sphere geometry that every qubit in a quantum computer lives on, the fiber bundles underlying gauge theory, and the quaternion math that runs inside every 3D graphics engine, embedding space, and robotics controller on the planet.
10 minutes. Bookmark & watch today. The most important shape nobody talks about.
