Hossenfelder Rebuts Musk Simulation Claim, Cites Superdeterminism

Sabine Hossenfelder

Delayed-choice double-slit measurements force physicists to choose between faster-than-light wave function collapse and superdeterminism, invalidating both textbook depictions of particle stripes and Elon Musk's video-game simulation theory.

AI-assisted summary of What everyone gets wrong about the double slit experiment — original source. Check the original for full context.

Source published: 2026-07-20

Key ideas

Popular science graphics showing the double slit interference pattern collapsing into two narrow stripes upon measurement are physically incorrect; observing the path produces two overlapping single-slit diffraction patterns. (0:00)
Delayed-choice double slit experiments demonstrate that wave function updates occur faster than light across spatial distances, leaving superdeterminism as the only alternative to Einstein's 'spooky action'. (3:00)
Transverse momentum is conserved in individual particle detections via quantum entanglement with the slit barrier itself, imparting an equal and opposite kick to the screen apparatus. (8:52)
Critiques of Elon Musk's simulation hypothesis highlight that quantum mechanics relies on irreducible randomness rather than deterministic pseudo-random algorithms used in video game rendering engines. (6:58)

Detailed notes

## Background Published on YouTube by physicist Sabine Hossenfelder on July 20, 2026, this video tackles the widespread misconceptions surrounding physics' most famous setup: the double slit experiment. As outlined in the description, Hossenfelder breaks down standard textbook animations and popular science fallacies to clarify what quantum mathematics actually demonstrates.

## TL;DR Hossenfelder deconstructs the common myth that detecting a particle at a slit collapses the interference pattern into two classical stripes, clarifying that particles still propagate as waves to produce overlapping single-slit diffraction patterns. She explains that the genuine quantum mystery stems from delayed-choice setups, which demand either faster-than-light wave function updates or superdeterminism to account for non-local or interaction-free measurements. Along the way, she dismantles Elon Musk's simulation hypothesis claims and New Age myths about human consciousness, emphasizing that inanimate detectors trigger measurement. Finally, she shows that momentum is conserved in individual particle runs through quantum entanglement with the slit apparatus, expressing exasperation that mainstream physics neglects the true tension between instantaneous collapse and relativity.

## Atmosphere & style The presentation carries Hossenfelder’s signature sardonic, no-nonsense delivery, pairing rigorous mathematical clarity with dry humor about internet misunderstandings and armrest-biting exasperation. Watching her feels like receiving a brisk, unapologetic reality check that cuts through decades of pop-science hype and tech-celebrity hot takes. Despite her trademark grumpiness, the tone remains pedagogically clear and urgently earnest about refocusing foundational physics on its real, unresolved problems.

## Bulletin - [00:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=0s) Popular science graphics showing the double slit interference pattern collapsing into two narrow stripes upon measurement are physically incorrect; observing the path produces two overlapping single-slit diffraction patterns. - [03:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=180s) Delayed-choice double slit experiments demonstrate that wave function updates occur faster than light across spatial distances, leaving superdeterminism as the only alternative to Einstein's 'spooky action'. - [08:52](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=532s) Transverse momentum is conserved in individual particle detections via quantum entanglement with the slit barrier itself, imparting an equal and opposite kick to the screen apparatus. - [06:58](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=418s) Critiques of Elon Musk's simulation hypothesis highlight that quantum mechanics relies on irreducible randomness rather than deterministic pseudo-random algorithms used in video game rendering engines.

## Key takeaways - [00:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=0s) The common textbook claim that unobserved particles act like waves while observed particles act like tiny billiard balls is fundamentally flawed. - [01:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=60s) When a detector observes which slit a particle traverses, the particle continues to behave as a wave, generating a standard single-slit diffraction pattern rather than a sharp line. - [02:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=120s) Mathematically, the double slit pattern arises from an interference cross-term; measuring which slit was traversed eliminates this cross-term, leaving the simple sum of individual diffraction probabilities. - [03:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=180s) The genuine mystery of quantum mechanics lies in delayed-choice experiments, where path measurement decisions are made after the particle has departed the source. - [04:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=240s) Interaction-free measurements, such as a detector remaining silent at one slit, instantaneously collapse the wave function to the opposite slit without any physical interaction. - [04:30](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=270s) To avoid faster-than-light wave function collapse, physics must accept superdeterminism, implying that future measurement choices are predetermined prior to emission. - [06:58](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=418s) Elon Musk's comparison of quantum measurement to video game rendering fails because the simulation hypothesis lacks a rigorous, falsifiable scientific definition. - [07:30](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=450s) Video games rely on deterministic pseudo-random algorithms, whereas true quantum processes are fundamentally non-deterministic and irreducibly random. - [08:05](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=485s) Measurement does not inherently confer 'positional certainty'; measuring an alternative observable like momentum yields momentum certainty while leaving position entirely indeterminate. - [08:30](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=510s) Human consciousness plays no role in quantum measurement; inanimate physical detectors achieve the exact same wave function collapse. - [08:52](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=532s) Individual off-center particle impacts conserve transverse momentum because the particle entangles with the slit barrier, transferring an equal and opposite momentum kick to the macroscopic apparatus. - [09:30](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=570s) If slit barriers are made small enough to detect this recoil momentum, such as using individual atoms, path information is revealed and the interference pattern is destroyed. - [10:15](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=615s) Mainstream physics neglects the critical foundational task of reconciling instantaneous wave function updates with the cosmic speed limit of special relativity.

## Detailed walkthrough ### [00:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=0s) The "Two Stripes" Myth and What the Math Actually Says

The double slit experiment is widely considered the most famous experiment in physics, but it is simultaneously the most misunderstood. Sabine Hossenfelder opens by pointing out that standard textbook and popular science animations mislead people right from the start. The textbook narrative typically claims that if particles lacked quantum mechanics, they would act like tiny billiard balls and form two simple stripes on the detection screen behind the slits; but because they exhibit wave properties, they form an alternating interference pattern that builds up particle by particle. Sabine dismisses the notion that particles behaving like waves is inherently mind-boggling: particles simply spread out, pass through both slits simultaneously, and interfere with themselves.

The widespread misconception arises when popularizers explain what happens when an observer measures which slit the particle went through. Popular graphics routinely show the interference pattern collapsing into two neat, sharp stripes of particle impacts. Sabine emphasizes that this is physically false: “If you observe which slit the particle goes through, say the right one, then the particles still behave like a wave.” The particle does not turn into a little ball; it behaves as a wave passing through only one slit, producing a standard single-slit diffraction pattern (which itself is an interference phenomenon). If you monitor which slit particles traverse and pool the data, the screen shows the smooth overlap of two diffraction patterns—never two narrow stripes.

```mermaid flowchart TD accTitle: Double Slit Wave Function Math vs Misconception accDescr: Diagram contrasting how single-slit diffraction patterns combine versus unmeasured quantum interference with cross-terms.

subgraph StandardObserved ["Observed Slit (Which-Way Known)"] A["Wave through Left Slit: ψ₁"] --> C["Probability: |ψ₁|²"] B["Wave through Right Slit: ψ₂"] --> D["Probability: |ψ₂|²"] C & D --> E["Total Pattern: |ψ₁|² + |ψ₂|²<br/>(Sum of individual diffraction patterns)"] end

subgraph Unobserved ["Unobserved Slits (Superposition)"] F["Total State: ψ₁ + ψ₂"] --> G["Total Probability: |ψ₁ + ψ₂|²"] G --> H["Expanded: |ψ₁|² + |ψ₂|² + Interference Term (2 Re[ψ₁* ψ₂])"] end ```

The mathematical distinction between both slits being open versus knowing the path comes down to basic quantum mechanics: - When both slits are unmeasured, the total wave function is the linear combination of the wave functions from both slits: $\psi_{\text{total}} = \psi_1 + \psi_2$. - The probability distribution on the screen is given by the squared magnitude: $P = |\psi_1 + \psi_2|^2 = |\psi_1|^2 + |\psi_2|^2 + 2\text{Re}(\psi_1^* \psi_2)$. - The square of the sum is not equal to the sum of the squares; the extra cross-term represents quantum interference. - When you detect which slit the particle passes through, you destroy the cross-term, yielding simply the direct addition of individual single-slit diffraction patterns ($|\psi_1|^2 + |\psi_2|^2$).

---

[03:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=180s) The Real Mystery: Delayed Choice, Spooky Action, and Superdeterminism

The true conceptual puzzle of the double slit experiment is not that particles produce single-slit patterns when observed; it is the fact that an experimenter can delay the decision to measure which slit the particle traverses until *after* the particle has already departed the source and passed the barrier. If a detector placed at one slit (for instance, the right slit) is turned on mid-flight, the system must account for that measurement before hitting the screen.

If the particle was sent with both paths open and no initial measurement, its state was described by a wave function traversing both slits. Turning on the detector forces an instantaneous update across spatial separation. The wave function must abruptly collapse from being in both slits to being strictly in either the left slit or the right slit. This update occurs faster than light: measuring or detecting at one slit instantaneously alters the physical state associated with the other slit.

Crucially, this collapse happens even when the detector does *not* click. If the right-slit detector remains silent, the experimenter immediately deduces the particle took the left slit. Sabine underscores the paradoxical nature of this interaction-free measurement: “If it doesn't go into the detector, you know it must have gone through the other slit. But if the particle went through the other slit, you never interacted with it.” To evade this faster-than-light update (Einstein's "spooky action at a distance"), the only alternative within standard spacetime is superdeterminism—the idea that the particle already "knew" whether the detector would be turned on before the experimenter consciously decided to switch it on. Sabine summarizes the dilemma: “You either have to accept a faster than light update of the wave function, the spooky action, or you have to accept that the future is fully determined already.”

---

[05:28](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=328s) Mid-Roll Interlude: The Armrest and the FlexiSpot Chair

Sabine steps away from the physics to address a running gag among her viewers: people frequently mock her for biting into her armrest whenever someone misrepresents quantum mechanics on the internet. She introduces the sponsor, FlexiSpot, and showcases their C7 Max ergonomic office chair.

She notes its practical advantages, particularly during heat waves where you do not stick to the fabric, and highlights that every component is fully adjustable: the armrests, the headrest, the seatback, and the overall height. She mentions that on her previous chair, she had to sit on an extra pillow constantly because the factory cushion was so thin it felt like sitting directly on steel. The standout feature for her is the integrated footrest, adding wryly that the only negative consequence is that her children now demand one for themselves. The chair includes a five-year warranty and a 30-day return policy.

---

[06:58](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=418s) Debunking Elon Musk’s Simulation Take and Consciousness Myths

Returning to physics, Sabine reiterates the real lesson: the mystery is not that particles possess wave-like nature, but that delayed-choice measurements require either superdeterminism or faster-than-light wave function updates. She uses this framework to critique a public statement made by Elon Musk, who claimed that the double slit experiment provides evidence for the simulation hypothesis because objects render with definite properties only when observed, analogous to video game optimization.

Sabine deconstructs Musk's claim across three distinct points: 1. **Meaninglessness of the Simulation Hypothesis:** Sabine notes that nobody can rigorously define what the universe being a computer simulation actually means, making it unfalsifiable. She remarks: “It's not even wrong, as Pauli said so aptly.” 2. **Pseudo-randomness vs. Quantum Randomness:** In practical game engines, random number generators are deterministic algorithms designed to look unpredictable (pseudo-random). Quantum processes are fundamentally, irreducibly random. If particles were computed via pseudo-random video game code, quantum mechanics could be simulated deterministically, overturning the standard interpretation: “If it were the case that particles in a double-slit experiment were indeed generated like in video games, that is, following a deterministic algorithm, then you'd be able to predict individual measurement outcomes.” 3. **Measurement and Definite Properties:** Musk claimed measuring an object gives it "positional certainty." Sabine points out that certainty is entirely contingent on the observable measured: measuring momentum yields momentum certainty while leaving position completely indeterminate.

Furthermore, Sabine dismantles the persistent New Age myth that quantum measurement requires human consciousness. Conscious observation is entirely unnecessary; an inanimate physical detection apparatus interacting with the particle provides the exact same measurement result.

---

[08:52](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=532s) Momentum Conservation and Why Sabine Is Grumpy

Sabine addresses a final subtle puzzle that confuses even professional physicists: momentum conservation in single particle runs. If an incoming particle travels perpendicular to the barrier, its initial transverse momentum is zero. Yet, after clearing the slits, it deflects at an angle to land on an off-center region of the interference pattern. While the average momentum over thousands of runs sums to zero, it appears on the surface that individual particle impacts violate conservation of momentum.

Sabine explains that momentum is strictly conserved in every single run because the particle becomes quantum-mechanically entangled with the slit apparatus itself. When a particle receives a transverse momentum kick toward one side of the screen, the double slit screen itself receives an equal and opposite momentum kick: - The kick imparted to the barrier is unmeasurable in practice solely because macroscopic slits are trillions of times more massive than an elementary particle. - If the slits are engineered to be tiny enough that their recoil momentum can be tracked—such as using individual atoms as slits, as demonstrated in recent experiments—that measurement entangles path information and destroys the interference pattern.

She concludes with why she remains permanently exasperated with the field: the endless cycle of pop-science nonsense and pseudo-philosophical confusion obscures the real foundational challenges. Physicists are not actively resolving the true mathematical problem: reconciling instantaneous wave function updates with Einstein's cosmic speed limit ($c$). Sabine considers this the single most pressing research problem capable of revitalizing the foundations of physics, yet it remains largely neglected by mainstream researchers.

## Notable quotes > [03:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=180s) You either have to accept a faster than light update of the wave function, the spooky action, or you have to accept that the future is fully determined already. — Sabine Hossenfelder

> [00:00](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=0s) If you observe which slit the particle goes through, say the right one, then the particles still behave like a wave. — Sabine Hossenfelder

> [06:58](https://www.youtube.com/watch?v=npc6Mn2CZV8&t=418s) If it were the case that particles in a double-slit experiment were indeed generated like in video games, that is, following a deterministic algorithm, then you'd be able to predict individual measurement outcomes. — Sabine Hossenfelder

## Mentioned Sabine Hossenfelder, FlexiSpot, C7 Max, Albert Einstein, Elon Musk, Wolfgang Pauli

## Video description Upgrade your setup with up to 50% Off during FlexiSpot's Mega Summer Sale! Enter my exclusive code 'C750' and save an extra $50 on the C7 Max chair! Shop through FlexiSpot C7 famliy!：https://go.flexispot.com/4qISRf -us https://go.flexispot.com/UTG9Xz -ca

In today's video I talk about some commonly misunderstood points in the double slit experiment.

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[Source](https://www.youtube.com/watch?v=npc6Mn2CZV8)

中文简报

霍森菲尔德驳斥马斯克模拟假说，援引超决定论延迟选择双缝测量迫使物理学家在超光速波函数坍缩与超决定论之间做出抉择，这既否定了教科书中关于粒子条纹的描绘，也推翻了埃隆·马斯克的电子游戏模拟理论。霍森菲尔德破除了一个常见误解，即在狭缝处探测粒子会使干涉图样坍缩为两条经典的粒子条纹；她澄清粒子仍会以波的形式传播，产生重叠的单缝衍射图样。她解释称，真正的量子谜团源于延迟选择实验，这类实验需要借助超光速波函数更新或超决定论，来解释非局域或无相互作用的测量。在此过程中，她驳斥了埃隆·马斯克的模拟假说以及有关人类意识的新时代神话，强调无生命特征的探测器同样能触发测量。最后，她指出在单个粒子的运行中，通过与狭缝装置的量子纠缠保证了动量守恒，并对主流物理学忽视瞬时坍缩与相对论之间真正的张力表示愤慨。科普图表中展示的“测量后双缝干涉图样坍缩为两条狭窄条纹”在物理学上并不正确；观测路径实际上会产生两个重叠的单缝衍射图样。 (0:00) 延迟选择双缝实验表明，波函数的更新跨越空间距离的速度快于光速，超决定论因此成为爱因斯坦所谓“鬼魅般的超距作用”的唯一替代选项。 (3:00) 在单粒子探测中，横向动量通过与狭缝屏障本身的量子纠缠得以守恒，对测量装置施加了大小相等、方向相反的反冲。 (8:52) 对埃隆·马斯克模拟假说的批评指出，量子力学依赖的是不可约简的随机性，而非电子游戏渲染引擎中使用的确定性伪随机算法。 (6:58)

Reading summary

Sabine Hossenfelder argues that popular science misrepresents the double-slit experiment by focusing on wave-particle duality and consciousness, obscuring the genuine foundational conflict between instantaneous wave function collapse and relativistic speed limits. The Two Stripes Fallacy and Diffraction Math (0:00) Popular science graphics frequently claim that observing which slit a particle traverses forces it to act like a classical billiard ball, producing two distinct impact bands on a detector screen. Hossenfelder clarifies that particles continue to behave as waves even when measured; detecting the path merely forces the particle to travel through a single slit, producing a standard single-slit diffraction pattern. When data from both monitored slits are compiled, the screen shows the smooth overlap of two diffraction patterns rather than two sharp stripes. The difference between observed and unobserved paths is mathematical. An unobserved particle enters a superposition where the total wave function is the sum of both paths, producing an intensity distribution that includes a quantum interference cross-term. When path detection occurs, this cross-term is eliminated, resulting in the direct sum of the individual single-slit diffraction probabilities. Delayed-Choice Measurement and Spooky Action (3:00) The deeper conceptual challenge in the double-slit setup arises during delayed-choice configurations, where an experimenter decides whether to activate a detector after the particle has departed the source and passed the slit barrier. Because the particle initially travels as a wave function passing through both slits, turning on a detector mid-flight requires an instantaneous physical update across space, forcing the wave function to collapse entirely to one slit or the other. This update occurs even during interaction-free measurements. If a detector placed at the right slit fails to click, the experimenter deduces the particle used the left slit despite never physically interacting with it. Hossenfelder stresses that avoiding this faster-than-light collapse requires accepting superdeterminism—the postulate that the particle's trajectory and the experimenter's measurement decision were predetermined before the run began. Deconstructing Simulation Hypotheses and Observer Myths (6:58) Hossenfelder critiques claims that the double-slit experiment supports the simulation hypothesis, such as Elon Musk's assertion that particles render definite values upon observation like video game optimization. She points out that the simulation hypothesis lacks a rigorous, falsifiable definition. Furthermore, video game engines generate pseudo-random numbers using deterministic code; if quantum events followed deterministic rendering algorithms, individual measurement outcomes would be predictable, which contradicts fundamentally irreducible quantum randomness. She also notes that measurement does not confer universal positional certainty, as measuring momentum renders position indeterminate. Additionally, Hossenfelder rejects the New Age concept that human consciousness causes wave function collapse. Measurement does not depend on a conscious observer; an inanimate physical detection device produces the exact same collapse and measurement outcomes. Momentum Conservation via Barrier Entanglement (8:52) A common point of confusion among physicists involves transverse momentum conservation. A particle fired perpendicular to the barrier enters with zero transverse momentum but frequently deflects at an angle to strike off-center interference fringes. Hossenfelder explains that momentum is conserved in every individual run because the particle entangles with the slit barrier, imparting an equal and opposite momentum kick to the apparatus. In standard experiments, this recoil is impossible to measure because macroscopic slit barriers are trillions of times more massive than an elementary particle. However, if an experiment employs atomic-scale slits capable of recording recoil momentum, tracking that physical recoil automatically yields path information, which subsequently destroys the quantum interference pattern. Hossenfelder concludes that popular science tropes and philosophical distractions divert research away from the most pressing foundational problem in modern physics: mathematically reconciling instantaneous wave function updates with Einstein's cosmic speed limit.

精炼阅读摘要

物理学家 Sabine Hossenfelder 指出，双缝实验常年遭受科普动画与流行文化的严重误导：对粒子路径的测量并不会使其变成形成“两条细纹”的微型台球，而是呈现单缝波衍射图样；该实验真正的物理学核心难题，在于延迟选择测量带来的超光速波函数坍缩与超决定论困境，而非神秘的意识参与或模拟宇宙假说。双条纹科普误区与单缝衍射数学本质 (0:00) 教科书和科普读物通常声称，如果没有量子力学，粒子会像经典小球一样在屏幕上打出两条笔直的条纹；而观测粒子穿过哪条狭缝会导致干涉图案消失，坍缩成这两条细纹。Hossenfelder 强调这一描绘在物理上完全错误。即便实验者观测到粒子穿过特定的一条缝（例如右缝），粒子依然表现为波，它穿过单一狭缝并展现出标准的单缝衍射图样（单缝衍射本身也是一种干涉现象）。若将测量两缝路径的数据汇总，屏幕上呈现的是两个平滑重叠的单缝衍射图样，绝不会收缩成两条锐利的小球撞击条纹。这一差异可以通过基础量子力学波函数严格解释。当两缝均处于未测量状态时，系统的总波函数是两缝波函数的线性叠加（ψ_total = ψ₁ + ψ₂），到达屏幕的概率分布由其模的平方决定，即包含干涉交叉项（2Re[ψ₁* ψ₂]），正是该交叉项构成了明暗相间的干涉条纹；一旦实验者探测并确定了粒子的路径，该干涉交叉项便被彻底摧毁，屏幕上的总概率仅为各自独立单缝衍射概率的直接相加（|ψ₁|² + |ψ₂|²）。粒子并未转变为实体小球，而是其波函数的叠加性在测量中发生了改变。延迟选择困境与超距波函数坍缩 (3:00) 双缝实验真正的概念谜题并非粒子具有波粒二象性，而是实验者可以在粒子已离开光源并穿过狭缝屏障之后，才“延迟决定”是否进行路径测量。如果在粒子飞行途中突然开启置于某一狭缝处的探测器，整个量子系统的波函数必须在粒子撞击屏幕前瞬间完成全局更新。这意味着原本弥散在两条狭缝的波函数，会即时坍缩至其中单一路径，这种状态的重置跨越了空间距离，其演化速度超越了光速。更具悖论意味的是“无相互作用测量”现象：假设在右侧狭缝设置了探测器，但该探测器并未被触发，实验者即可立即推断粒子必定穿过了左侧狭缝。尽管探测器从未与粒子发生任何实际的物理接触，左侧波函数依然发生了瞬间坍缩。Hossenfelder 指出，面对这种超越光速的瞬时波函数更新（即爱因斯坦所指的“鬼魅般的超距作用”），在现有标准时空框架下的唯一替代解释是“超决定论”（Superdeterminism）——即假定在粒子发射之初，整个宇宙的初始条件就已经预先确定了实验者未来的开启决策。物理学界必须在瞬时超光速波函数更新与完全被决定的未来之间做出抉择。对模拟宇宙假说及意识论的反驳 (6:58) Hossenfelder 针对埃隆·马斯克（Elon Musk）将双缝实验引申为“宇宙是一场计算机模拟”的言论提出了严厉反驳。马斯克曾主张物体仅在被观察时才被渲染出确定属性，类似于现代电子游戏为了节省算力而采取的视锥体优化机制。Hossenfelder 从三个科学层面解构了这一说法：首先，模拟假说本身缺乏严格的数学与操作性定义，在科学上是不可证伪的，正如泡利（Pauli）的名言所指“连错误都算不上”；其次，电子游戏引擎使用的是确定性算法生成的“伪随机数”，而量子力学的随机性在本质上是不可简化的绝对随机，若量子力学真由游戏代码驱动，人类理应能推导出确定性规律并预测单次测量结果；最后，测量所赋予的确切性完全依赖于具体观测量，测量动量只能带来动量确定性，同时会导致位置极度不确定，绝非通用的空间位置优化渲染。此外，针对长期盘踞在流行文化中的“新时代”（New Age）神秘主义观点，Hossenfelder 明确反驳了“人类意识导致波函数坍缩”的说法。量子力学中的测量纯粹是指微观系统与宏观环境或检测仪器发生相互作用并产生退相干，任何无生命的物理测量装置都可以独立产生完全相同的测量效应，与人类意识的存在与否毫无关联。单粒子动量守恒与狭缝装置纠缠 (8:52) 即使是专业物理学家，也常常对单粒子运行下的动量守恒感到困惑：若入射粒子完全垂直于狭缝屏障飞来，其初始横向动量为零；但在穿过狭缝后，粒子往往以一定偏转角击中偏离中心的屏幕区域。尽管成千上万次撞击的平均横向动量统计值为零，但在单次实验中，粒子似乎凭空获得了侧向动量，表面上违反了动量守恒定律。 Hossenfelder 阐明，在每一次单独的粒子撞击过程中，动量都得到了绝对严格的守恒，这是因为粒子在穿越狭缝时与双缝屏障本身发生了量子纠缠。当粒子向一侧偏转获得横向动量时，双缝屏必然获得一个大小相等、方向相反的反冲动量；宏观双缝装置的质量比基本粒子大上万亿倍，导致该反冲在常规实验中无法被直接探测到。然而近期的前沿物理实验表明，如果将狭缝微缩为单个原子以使其反冲动量能够被测量，那么对狭缝反冲的精确测量将不可避免地锁定粒子的路径信息，进而彻底摧毁屏幕上的量子干涉图样。 Hossenfelder 总结认为，科普领域层出不穷的错误图景与伪哲学炒作转移了大众的视线，掩盖了量子力学真正的基础性危机。主流物理学界长期回避了核心数学矛盾：即波函数的瞬时空间更新如何与爱因斯坦狭义相对论的光速上限（c）实现自洽协调。她呼吁理论物理学家停止纠缠于无意义的臆想，重新直面这一能够彻底革新物理学基石的重大未决难题。

Source quotes

[3:00] Sabine Hossenfelder: You either have to accept a faster than light update of the wave function, the spooky action, or you have to accept that the future is fully determined already. [0:00] Sabine Hossenfelder: If you observe which slit the particle goes through, say the right one, then the particles still behave like a wave. [6:58] Sabine Hossenfelder: If it were the case that particles in a double-slit experiment were indeed generated like in video games, that is, following a deterministic algorithm, then you'd be able to predict individual measurement outcomes.

Original transcript

[0:00] The double slit experiment is the probably most famous experiment ever and also the most misunderstood one. In this video I'll tell you why it confuses even physicists, what the double slit experiment has to do with Einstein's spooky action, what Elon Musk got wrong about it, and why Sabina is permanently grumpy. The typical illustration of the double slit experiment looks something like this: if particles did not have quantum properties, they'd behave like little just form two stripes on the screen. But if they do have quantum properties, they form an interference pattern which builds up from single particles. Okay, but so what? All this shows is that particles have wave-like properties. Particles aren't little points, they spread out like waves, so they can go through both slits at the same time. And that's why the parts of the wave coming from each single even for a single particle. That's what creates the pattern. The only thing that's weird is that some people think elementary particles should behave like little balls. Well, the explanation goes, the weird part is that if you observe which of the slits the particle went through, then the particles stop behaving this way. They form just two stripes on the screen. That is allegedly stop behaving like waves or form two stripes on the screen. This just never happens. If you observe which slit the particle goes through, say the right one, then the particles still behave like a wave. It's just that it's now a wave that goes through only one slit. It'll then form a diffraction pattern on the screen, which is also an interference effect. And likewise for the right slit. If you observe the particles, they will not give you two stripes on the screen. Instead, overlap of the two diffraction patterns. What's correct is that if you know which slit the particle went through, you do not get an interference from both slits. You get a sum of left slit and right slit. So what happens in the double slit experiment is that if you take the result of only the right slit and add it to the result of only the left slit, you do not get the same as having both slits open at once. The mathematical reason for this is rather simple. If you have two slits, functions from each slit, but the probability is the absolute square, and the square of the sum is not the sum of the squares. So for the double slit, you get an extra term. That's the interference term. But then the double slit experiment just seems to say that if you know the particle only goes through one slit at a time, then you get the pattern from only one slit at a time. And again, surprising about the double slit experiment. It's that you can decide whether or not to measure which slit the particle goes through after you send the particle on the way. Suppose you send the particle from here. There are always some particles that hit outside the slits, but these are not relevant, so we can just ignore them. And you put a detector in one of the slits, let's say the right one. You can either leave the detector off or you turn it on after the particle left the and before it appeared on the screen. Now we've just seen that to explain what happens on the screen. If we don't know which slit the particle went through, it needs to go through both slits. And if we do know which one it goes through, it goes through only one. The issue is then, that if you turn the detector on, the wave function of the particle must suddenly update on both slits. It must jump from a wave function that goes through both slits at once to one that either goes left or goes right but not both. And that update is instantaneous faster than night. slit and the wave function on the other slit changes immediately. And note that this is the case even if the particle does not trigger the detector. If it doesn't go into the detector, you know it must have gone through the other slit. But if the particle went through the other slit, you never interacted with it. You didn't touch the particle. It just knew you were trying to. The only way that you can avoid this faster the light update is that the particle knows whether you'll measure it before you've made the decision whether to [5:00] to measure it or not. This is what's called super determinism. And this is what's so weird about the double slit. You either have to accept a faster than light update of the wave function, the spooky action, or you have to accept that the future is fully determined already. And no, this actually has nothing to do with what happens on the screen. The screen is just the evidence for what happened at the slits. Thank you. I know you've been making fun of me for biting into my armrest each time someone gets quantum mechanics wrong, which is why I'm happy to say that I have a new chair from today's sponsor, FlexiSpot. This chair is called the C7 Max and it's absolutely great. For one thing, it's super comfortable to sit in, even during a heat wave. You don't stick to the chair and you can adjust everything about it. The armrest, the headrest, the seat on the back and of course the height. I actually had a pillow on the old chair most of the time because the cushion was so thin it was basically sitting on steel. Now what do I do with the pillow? But the coolest part is this. It has a footrest. Only downside is that now my kids want one too. I'm happy to recommend the chair from FlexiSpot. It's simply a great product and it comes with a five year warranty and a 30 day return policy. And yes, of course, I have a special offer. Had to FlexiSpot.com and use my code for an amazing discount. And now back to the physics. goes through, it uses its wave properties, it's that the particle must have known whether you'd measure it or not before you yourself knew. That, or faster than light, spooky action. Speaking of misconceptions, here is what Elon Musk recently had to say about the double set experiment: "It's consistent with the simulation hypothesis. Like a video game, objects are observed. The simulation hypothesis is the idea that the entire universe, including us, is a computer simulation. The problem with the idea is that no one knows what this means. This is why everything is compatible with it. It's not even wrong, as Pauli said so aptly. The second problem is that objects in a video game are usually not truly randomly generated. While this is possible in principle, in practice, it's rarely done because the only truly random processes are quantum mechanics. Usually video game algorithms are pseudo-random, which means they're created algorithmically just by an algorithm that's very hard to predict. If it were the case that particles in a double-slit experiment were indeed generated like in video games, that is, following a deterministic algorithm, predict the current standard interpretation of quantum mechanics. And I'd really like to know the algorithm. And third, it's not true that measuring an object gives it positional certainty that depends on what you measure. If you measure momentum, then it's the momentum that obtains certainty, not the position. While I'm at it though, there are two other common misunderstandings consciousness. That just isn't so. The measurement doesn't have to be done by a conscious observer. Some operators will do. The other thing that even physicists are often confused about is momentum conservation. Because suppose the initial particles you sent went straight ahead and at the plate, but then you measure a particle over here. Clearly that's changed its direction, but that should be at the average of all the particles, then the total momentum again goes straight ahead and that's fine. But it still seems that in single runs it isn't conserved. That is wrong. What actually happens is that the particle becomes entangled with the double slit itself. If the particle gets a small momentum kick into this direction, then the screen gets a little kick into the other direction run. It's just that because the double slit is so much heavier than a single particle, you can't measure this tiny kick. And the corollary is, if the slit was so small that you could measure its momentum, then that would at least partially destroy [10:00] the interference again. You can do this if you use individual atoms as the slits. Indeed, this was done in a recent paper, which I talked about in an earlier video. So the reason why Sabine is constantly grumpy is that most of the talk about why quantum mechanics are supposedly weird is just nonsense. And each time I look, there's more nonsense. And all this nonsense is why we aren't the instantaneous update of the wave function compatible with Einstein's speed of light limit. This is a perfectly obvious research problem that basically no one's working on, despite the fact that it's the one topic that could actually return the foundations of physics to relevance. But at least I have a new chair now. Life is good. So head to flexisport.com and grab yours. By the way, to support this channel. Thanks for watching. See you tomorrow.