Mathematicians Attack Dark Energy But New Model Fails Cosmic Tests

Sabine Hossenfelder

A mathematical challenge claiming the universe accelerates without dark energy falls flat because it fails to confront decades of precision cosmological data.

AI-assisted summary of The Dark Energy Mistake that Fooled Physicists' for 25 Years — original source. Check the original for full context.

Source published: 2026-07-14

Key ideas

A new mathematical paper argues that cosmic acceleration can emerge naturally from instabilities in general relativity without invoking dark energy or negative pressure. (0:00)
The authors challenge the cosmological principle by showing that a uniformly expanding matter-filled universe is unstable, inevitably fragmenting into patches with varying local expansion rates. (2:06)
Sabine Hossenfelder rates the paper a 6 out of 10 on her 'bullshit meter' because it offers rigorous mathematics without confronting precision observational datasets like the CMB, BAO, or supernovae. (4:13)

Detailed notes

## Background Published on YouTube by physicist Sabine Hossenfelder on July 14, 2026, this video examines a newly published mathematical paper that challenges the foundational necessity of dark energy. The description highlights that while physicists have long attributed the accelerating expansion of the universe to dark energy with negative pressure, the paper suggests that this multi-decade assumption may stem from a mathematical oversight rather than physical reality.

## TL;DR For twenty-five years, mainstream cosmology has explained the accelerating expansion of the universe by invoking dark energy—an unobserved substance with negative pressure that supposedly constitutes over 75% of the cosmos. A new paper by mathematicians argues that uniform expansion is dynamically unstable, meaning pure matter with small perturbations naturally splits into inhomogeneous regions where expansion accelerates locally without needing dark energy. However, while acknowledging the clever mathematics, Sabine Hossenfelder gives the proposal a 6 out of 10 on her 'bullshit meter' because it fails to fit the extensive body of empirical observational data—such as supernovae, the cosmic microwave background, and baryon acoustic oscillations—that keeps dark energy entrenched in modern astrophysics.

## Atmosphere & style The presentation is crisp, sardonic, and unapologetically pragmatic, characterized by Hossenfelder's trademark no-nonsense demeanor. She blends sharp scientific scrutiny with dry humor, moving smoothly from dissecting abstract dynamical systems to cutting through academic hype with grounded skepticism. The viewing experience feels like a candid, reality-checking masterclass where elegant theoretical abstractions are swiftly weighed against the messy, unyielding demands of experimental observational data.

## Bulletin - [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) A new mathematical paper argues that cosmic acceleration can emerge naturally from instabilities in general relativity without invoking dark energy or negative pressure. - [02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) The authors challenge the cosmological principle by showing that a uniformly expanding matter-filled universe is unstable, inevitably fragmenting into patches with varying local expansion rates. - [04:13](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=253s) Sabine Hossenfelder rates the paper a 6 out of 10 on her 'bullshit meter' because it offers rigorous mathematics without confronting precision observational datasets like the CMB, BAO, or supernovae.

## Key takeaways - [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) Approximately 25 years ago, astronomical observations revealed that the expansion of the universe is accelerating over time. - [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) Standard general relativity requires an exotic substance with negative pressure—dubbed dark energy—to produce cosmic acceleration. - [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) Dark energy is currently estimated to account for more than 75% of the total energy budget of the universe. - [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) Despite dominating the cosmos, dark energy has never been directly detected in laboratory experiments, leaving its physical nature unknown. - [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) Recent observational data suggest dark energy may change over time rather than behaving as a static cosmological constant, complicating theoretical models. - [02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) A new mathematical paper contends that standard cosmology took an unnecessary shortcut by assuming dark energy was present from the beginning. - [02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) Dynamical systems analysis of Einstein's equations indicates that a smoothly expanding matter-dominated universe is mathematically unstable. - [02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) The instability implies the universe would fragment into domains with differing local expansion rates, some of which naturally accelerate. - [02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) The paper challenges the cosmological principle, comparing the assumption of large-scale homogeneity to keeping a pencil balanced perpetually on its tip. - [02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) If the mathematical model is valid, our observable universe could merely be located inside an accelerating patch, removing the need for dark energy. - [04:13](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=253s) A primary flaw of the paper is its failure to compare its mathematical predictions against empirical observations such as Type Ia supernovae and the CMB. - [04:13](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=253s) The standard Lambda-CDM model remains entrenched because it successfully matches precision data across multiple distinct cosmological probes.

## Detailed walkthrough ### [00:00](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=0s) The Postulation of Dark Energy and Its Growing Problems

About twenty-five years ago, astrophysicists uncovered evidence that the universe is not merely expanding, but that its expansion is speeding up over time. While incorporating time-varying expansion into Einstein’s field equations poses little mathematical challenge, resolving it physically proved troublesome. Producing an accelerated expansion within standard general relativity demands an exotic substance possessing negative pressure—a phenomenon unseen anywhere in known laboratory physics. To bridge this gap, physicists simply postulated that this entity exists and christened it "dark energy." However, a recent mathematical paper argues that this entire premise was an unnecessary detour, contending that the equations of general relativity generate accelerating expansion on their own without exotic ingredients. Sabine Hossenfelder emphasizes the stakes of this critique: “If they are right, that would be the ultimate embarrassment for physicists.”

Over the intervening decades, dark energy has evolved into a persistent conceptual headache. If real, it is not a marginal background effect; it must account for over three-quarters of the entire energy budget of the universe. Yet despite dominating the cosmos, it cannot be detected or measured in laboratories on Earth, and physicists remain completely in the dark regarding its underlying physical nature. Complicating matters further, recent observational datasets challenge the original, simplest hypothesis that dark energy acts as a static cosmological constant. Instead, emerging measurements imply that dark energy may vary over time, prompting astrophysicists to assemble ad-hoc theoretical justifications after the fact.

- Accelerated cosmic expansion was discovered roughly 25 years ago via astronomical observations. - Standard physical models require an unobserved form of energy with negative pressure to drive this acceleration. - Dark energy is calculated to comprise more than 75% of the total energy density of the universe. - Recent observational datasets increasingly suggest dark energy may change across cosmic time rather than staying constant.

```mermaid flowchart TD accTitle: Standard Model vs Mathematical Alternative accDescr: Flowchart comparing the standard cosmological model relying on dark energy with the mathematicians alternative based on gravitational instabilities.

subgraph StandardModel["Standard Cosmological Model"] A["Cosmological Principle<br/>(Homogeneous & Isotropic)"] --> B["Smooth Matter Expansion"] B --> C["Requires Dark Energy<br/>(Negative Pressure)"] C --> D["Accelerated Cosmic Expansion"] end

subgraph NewPaper["Mathematicians' Dynamic Formalism"] E["Matter with Inhomogeneities"] --> F["Even Expansion is Unstable<br/>(Pencil Balanced on Tip)"] F --> G["Inhomogeneous Patching"] G --> H["Local Accelerating Region<br/>(No Dark Energy Needed)"] end ```

---

[02:06](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=126s) The Mathematical Challenge to the Cosmological Principle

The central contention of the mathematicians' paper is that the physics community took a flawed mathematical shortcut. Typical cosmological frameworks assume that dark energy was present from the beginning of time. The authors of the paper take a different tack, asking what happens if the universe starts purely with matter containing tiny initial deviations from an otherwise smooth distribution. In standard cosmology, dark matter alone causes the expansion to decelerate as gravity pulls matter together into stars and galactic clusters. However, utilizing dynamic systems analysis to evaluate the stable states, unstable states, and attractors of Einstein’s equations, the authors find that a uniformly expanding matter-dominated cosmos is fundamentally unstable.

Because this perfectly uniform expansion is physically unrealistic, a matter-filled universe would inevitably fragment into distinct domains with wildly differing local expansion rates. Within some of these patches, the expansion naturally accelerates. Under this framework, our observable universe merely happens to reside inside one of these accelerated sectors, obviating any requirement for dark energy. This divergence from standard astrophysics stems directly from abandoning the cosmological principle—the longstanding foundational axiom that the universe is homogeneous and isotropic on large scales. The authors liken assuming a perpetually uniform expansion to expecting a pencil to remain perpetually balanced on its sharp tip: an abstraction existing solely in mathematical idealizations. As Hossenfelder notes of their core thesis: “The authors of the new paper say that physicists have simply screwed up the mathematics.”

- The standard assumption that dark energy was present at cosmic inception is discarded in favor of analyzing pure matter distributions with initial perturbations. - Dynamical systems analysis demonstrates that uniform, smooth matter expansion is mathematically unstable. - The cosmos naturally splits into sub-regions exhibiting differing rates of expansion, some of which accelerate. - The critique strikes directly at the cosmological principle, treating large-scale homogeneity as an unphysical idealization.

---

[04:13](https://www.youtube.com/watch?v=u61NFqZPpcQ&t=253s) Observational Reality Checks and Practical Solutions

While praising the paper's mathematical rigor, Hossenfelder points out a critical shortcoming: the mathematicians derived formal differential equations without confronting them with real observational data. Overturning standard cosmology requires far more than demonstrating an instability in an idealized model; any replacement theory must match the vast body of precision cosmological measurements collected over decades. These include data from Type Ia supernovae, the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), gravitational lensing, and large-scale structure formation. The prevailing Lambda-CDM model remains the standard not out of an affection for mysterious components, but because its calculations successfully align with this diverse empirical evidence. Summarizing her verdict, Hossenfelder remarks: “This is why I give the paper a 6 out of 10 on the bullshit meter: nice maths, not much physics.”

Consequently, dark energy is not going anywhere in mainstream astrophysics in the immediate future, both because it satisfies observational constraints and because the scientific community is already heavily invested in the current framework. Transitioning from cosmological scale problems to mundane practical ones, Hossenfelder shifts to discussing travel connectivity. She highlights Saily, an electronic SIM (eSIM) service designed to bypass expensive international carrier roaming fees by provisioning local cellular data packages directly through an app. The service is also handy for repurposing older smartphones that lack physical SIM cards or establishing virtual locations.

- A valid cosmological framework must fit diverse observational datasets: supernovae, cosmic microwave background, baryon acoustic oscillations, gravitational lensing, and cosmic structure growth. - The video awards the paper a score of 6/10 on the "bullshit meter" for delivering elegant mathematics that lacks observational physical verification. - Dark energy remains the standard model fixture because of empirical utility and institutional momentum. - Saily offers eSIM data plans to eliminate overseas roaming charges, featuring app-based setup, 24/7 technical support, a money-back guarantee, and an exclusive 15% discount using promo code `SABINE`.

## Mentioned Sabine Hossenfelder, Albert Einstein, Saily, Patreon, Substack, Donorbox, Spotify, YouTube

## Video description 🌎 Get an exclusive 15% discount on Saily data plans! Use the code SABINE at checkout. Download the Saily app or go to: https://saily.com/sabine ⛵

About 25 years ago, astrophysicists noticed that the universe’s expansion is accelerating. To account for this observation, physicists came up with a new type of energy – called dark energy – which supposedly makes up more than 75% of the universe, and also has negative pressure. In a new paper, mathematicians claim that dark energy isn’t needed to explain that accelerating expansion, and physicists have been barking up the wrong tree for decades. Let’s take a look.

Paper: https://doi.org/10.1098/rspa.2025.0912

#science #physics #universe #cosmos #sciencenews

👕T-shirts, mugs, posters and more: ➜ https://sabines-store.dashery.com/ 💌 Support me on Donorbox ➜ https://donorbox.org/swtg 👉 Transcript with links to references on Patreon ➜ https://www.patreon.com/Sabine 📝 Transcripts and written news on Substack ➜ https://sciencewtg.substack.com/ 📩 Free weekly science newsletter ➜ https://sabinehossenfelder.com/newsletter/ 👂 Audio only podcast ➜ https://open.spotify.com/show/0MkNfXlKnMPEUMEeKQYmYC 🔗 Join this channel to get access to perks ➜ https://www.youtube.com/channel/UC1yNl2E66ZzKApQdRuTQ4tw/join 📚 Buy my book ➜ https://amzn.to/3HSAWJW Did physicists make a mistake with dark energy? See why new math suggests we might not need this theory to explain universe expansion.

This video explores a recent claim by a group of mathematicians challenging the foundation of dark energy. If their calculations hold up, it would signal a major shift in modern astrophysics. We break down the original observations from 25 years ago that suggested the universe expansion is accelerating and compare them against these new mathematical findings.

[Source](https://www.youtube.com/watch?v=u61NFqZPpcQ)

中文简报

数学家挑战暗能量理论，但新模型未能通过宇宙学观测检验一项声称宇宙无需暗能量即可加速膨胀的数学挑战宣告受挫，因其未能经受住数十年精确宇宙学数据的检验。二十五年来，主流宇宙学一直通过引入暗能量来解释宇宙的加速膨胀；暗能量是一种具有负压强的未被观测到的物质，据推测占宇宙的75%以上。数学家们的一篇新论文提出，均匀膨胀在动力学上是不稳定的，这意味着带有微小扰动的纯物质会自然分裂成非均匀区域，在这些区域内无需暗能量即可局部加速膨胀。然而，尽管认可其数学上的巧妙之处，Sabine Hossenfelder仍在她的“胡说八道测量仪”上给该提议打了6分（满分10分），因为它无法契合大量的实证观测数据——例如超新星、宇宙微波背景辐射以及重子声学振荡，而正是这些数据让暗能量在现代天体物理学中牢固确立。一篇新的数学论文指出，宇宙加速膨胀可以自然地由广义相对论中的不稳定性产生，而无需引入暗能量或负压强。 (0:00) 作者对宇宙学原理提出质疑，表明一个均匀膨胀且充满物质的宇宙是不稳定的，必然会碎裂成具有不同局部膨胀速率的碎片区域。 (2:06) Sabine Hossenfelder在她的“胡说八道测量仪”上给这篇论文打了6分（满分10分），因为该论文虽提供了严谨的数学推导，却并未经受CMB、BAO或超新星等精确观测数据集的检验。 (4:13)

Reading summary

A new mathematical study argues that accelerating cosmic expansion can emerge naturally from gravitational instabilities without invoking dark energy, though Sabine Hossenfelder emphasizes that the proposal remains untested against real observational data. The Persistent Conceptual Dilemma of Dark Energy (0:00) Accelerated cosmic expansion, uncovered through astronomical observations roughly 25 years ago, forced physicists to adapt standard general relativity by introducing an unobserved substance with negative pressure called dark energy. Today, dark energy is calculated to comprise more than 75% of the total energy density of the universe. Despite its cosmological dominance, it has never been detected in terrestrial laboratories, leaving physicists uncertain about its fundamental nature. The theoretical challenge has deepened with recent observational datasets that challenge the simplest hypothesis of a static cosmological constant. These emerging measurements suggest dark energy might change across cosmic time, forcing astrophysicists to devise ad-hoc theoretical justifications to keep the standard model intact. Mathematical Instability and the Cosmological Principle (2:06) The mathematical critique targets the longstanding cosmological principle, the axiom that the universe is homogeneous and isotropic on large scales. While standard models assume dark energy was present from cosmic inception, the authors analyzed what occurs when Einstein's field equations govern a universe filled purely with matter containing slight initial density deviations. Using dynamical systems analysis, they found that perfectly uniform cosmic expansion is mathematically unstable. According to the authors, assuming perpetual smooth expansion is as physically unrealistic as expecting a pencil to remain balanced on its tip. Instead, a matter-filled cosmos naturally fragments into separate domains with differing local expansion rates, some of which accelerate. If our observable universe resides inside such an accelerating patch, general relativity accounts for the observed acceleration without requiring any exotic, negative-pressure dark energy. Empirical Constraints and Theoretical Evaluation (4:13) While acknowledging the mathematical elegance of the paper, Hossenfelder stresses that deriving formal differential equations is insufficient to displace established physics. The reigning Lambda-CDM framework remains the standard model not out of theoretical preference, but because it accurately fits a comprehensive body of precision empirical data, including Type Ia supernovae, the cosmic microwave background, baryon acoustic oscillations, gravitational lensing, and large-scale structure formation. Because the authors developed their model in isolation from these observational datasets, Hossenfelder assigns the study a score of 6 out of 10 on her 'bullshit meter,' summarizing the work as strong mathematics with little physical grounding. Consequently, the physics community's reliance on dark energy is expected to persist until alternative models can reproduce the observational successes of the standard framework. Dark energy remains entrenched in mainstream astrophysics due to institutional momentum and its empirical alignment with extensive cosmological data. For any mathematical alternative based on gravitational instabilities to succeed, it must move beyond theoretical derivations and match precision observational measurements.

精炼阅读摘要

物理学家兼科普作家 Sabine Hossenfelder 指出，尽管最新数学论文主张无须引入暗能量即可通过引力不稳定性解释宇宙加速膨胀，但因其缺乏与实际天文观测数据的对照，目前尚不足以推翻现有的标准宇宙学模型。暗能量假说的提出与困境 (0:00) 大约 25 年前，天文学家通过观测发现宇宙正在加速膨胀。在爱因斯坦的标准广义相对论框架下，产生加速膨胀需要一种具有负压强的奇特物质，而这种性质在已知实验室物理中从未被发现。为了填补这一理论空白，物理学界假设存在这种物质并将其命名为“暗能量”。根据现有计算，暗能量占据了整个宇宙总能量预算的 75% 以上，但物理学家至今无法在地球实验室中对其进行检测，对其物理本质也一无所知。近年来暗能量模型面临越来越大的理论挑战。早期最简单的假设认为暗能量是恒定的宇宙学常数，但最新的观测数据集显示暗能量可能随着宇宙演化时间而发生变化，迫使天体物理学家事后拼凑各种特设性理论来进行解释。如果暗能量假设最初就是不必要的理论弯路，对整个物理学界而言将是一次巨大的尴尬。数学动力学对宇宙学原理的挑战 (2:06) 最新发表的一篇数学论文指出，物理学界此前可能在数学推导上走入了误区。标准宇宙学模型建立在宇宙学原理之上，即假设大尺度宇宙是均匀且各向同性的，并认为暗能量从宇宙开端就已存在。然而，该论文作者采用动力学系统理论分析爱因斯坦场方程的稳定性状态与吸引子，探索如果宇宙初始仅由纯物质构成且存在微小扰动时会发生什么。该研究发现，一个由物质主导且完全均匀膨胀的宇宙在数学上是极其不稳定的，论文作者将其比作一根试图用笔尖永久直立的铅笔。由于完美均匀膨胀在物理上难以维持，物质宇宙将不可避免地分裂成具有不同局部膨胀速率的独立区域。在某些区域内，膨胀会自然发生加速。论文作者认为，人类所处的观测宇宙恰好位于其中一个加速膨胀的局部区域，从而完全无须借助暗能量的存在。缺乏观测验证的理论局限 (4:13) 尽管该数学论文在形式推导上具有严密性，但 Hossenfelder 认为其存在致命缺陷：作者仅推导出了形式化的微分方程，完全没有结合实际的天文观测数据进行验证。要替代现行的标准模型，仅证明理想化模型中的不稳定性是远远不够的，新理论必须能够拟合过去数十年累积的大量高精度观测数据，包括 Ia 型超新星、宇宙微波背景辐射（CMB）、重子声学振荡（BAO）、引力透镜以及大尺度结构形成等证据。主流学界之所以坚持包含暗能量的 Lambda-CDM 模型，并非出于对神秘成分的偏好，而是因为它在定量上成功吻合了上述多维度的经验观测。Hossenfelder 据此给这篇论文打出了“废话指数” 6 分（满分 10 分）的评价，称其展现了“漂亮的数学，但缺乏物理实质”。由于经验实用性以及科研体制的既有投入，暗能量在短期内依然不会被主流天体物理学抛弃。该论文展示了仅凭非均匀物质分布产生加速膨胀的纯数学可能性，但由于缺乏与超新星、宇宙微波背景辐射等核心观测数据的定量拟合，暗能量目前仍是解释宇宙加速膨胀最具实证支撑的标准范式。

Original transcript

[0:00] Physicists may have made a huge mistake when they introduce dark energy. [0:05] This is what a team of mathematicians say after looking at the equations. [0:11] Because they find that actually dark energies are necessary. If they are right, [0:16] that would be the ultimate embarrassment for physicists. Let's have a look. About 25 years ago, [0:23] astrophysicists noticed that the universe does not just expand. The expansion is getting faster too. [0:30] This doesn't sound like a big difference, okay so we thought the universe expands. Now the expansion [0:35] also changes in time. That can't be so difficult to include into the equations. And indeed, [0:41] it's not difficult to include mathematically. The problem is entirely on the physical side. [0:47] To get the expansion to accelerate, you need a peculiar sort of energy with negative pressure. [0:53] There's no such energy that we know of. So physicists just postulated that it exists [0:59] and called it dark energy. The authors of the new paper now say that this extra ingredient was never [1:05] needed. The expansion of the universe speeds up simply because Einstein's equations do that [1:11] anyway. This would be amazing because dark energy has become a big expanding headache [1:17] and the headaches expansion seems to be speeding up as well. You see, dark energy, if it exists, [1:23] is not a small contribution to the universe. It would have to make up most of the energy, more [1:29] than three quarters. Despite that, we supposedly can't measure it anywhere on Earth. It just sits [1:36] there doing nothing. We also don't know what, if anything, it's made of. And in the past years, [1:42] it's become clear that the simple idea that dark energy is just a constant contribution [1:48] doesn't quite work. We now have multiple sets of data that require dark energy to change in time. [1:54] And astrophysicists are busy cooking up reasons in hindsight explain why it actually has to be [2:00] this way. The authors of the new paper say that physicists have simply screwed up the mathematics. [2:07] You see, physicists usually assume that dark energy is just there since the beginning of [2:12] the universe. This team of mathematicians instead asks, "Okay, but what if it's not there?" Instead, [2:19] they look at the first moments of the universe without dark energy. They just put matter into [2:25] the universe, not perfectly smooth, but with small deviations from this smooth distribution. Over [2:31] time, gravity will make the matter clump, which creates stars and later galaxies. The presence [2:37] of dark matter alone makes the universe expand, we know this, but it doesn't make the expansion [2:44] accelerate. This is the usual problem. But the mathematicians find that the case in which the [2:50] universe expands evenly due to the presence of matter is unstable. It's a mathematically ideal [2:57] case that doesn't make physical sense. In reality, they say such a matter-filled universe would not [3:02] expand evenly. It would fall apart into regions with different expansion rates. In some regions, [3:08] the expansion accelerates. So they say we live in one of those regions where the expansion happens [3:13] to accelerate and that's it. No dark energy necessary. The reason they get a different result [3:19] from what astrophysicists normally get is that they remove one important assumption which is that [3:25] the universe is on average the same everywhere. It's called the cosmological principle. The [3:30] interesting thing about the paper is that their mathematical treatment is totally different from [3:35] what physicists usually do. They use a formalism that lets them study the stable and unstable [3:42] configurations and the attractors of the entire system. The general idea that physicists have [3:48] oversimplified their description of the universe and cause themselves problems that don't exist [3:54] is not new. What's different about these mathematicians analysis is that they found [3:59] a way to prove that the cosmological principle is physically highly questionable. It's like the [4:05] example of a pencil balanced on its tip. It exists only in Plato's ideal world of mathematics. That [4:13] all sounds intriguing and I do think it's a nice paper. But this is a paper from mathematicians. [4:20] They derive equations and this is all well and good. But they don't check whether the results [4:25] of their calculations agree with the observations and that's a high demand. Their idea would have [4:31] to fit all the cosmological data. Supernovae, the cosmic microwave background, baryon acoustic [4:38] oscillations, lensing, structure formation, etc. The currently used standard model of cosmology, [4:43] the one with dark energy, is not popular because cosmologists enjoy mysterious ingredients, well not [4:50] only because of that. It's popular because despite its shortcomings, it fits a lot of data. This is [4:56] why I give the paper a 6 out of 10 on the [ __ ] meter. nice maths, not much physics. So, for now, [5:03] dark energy remains in the model, mostly because it fits the data and partly because cosmologists [5:10] have already printed the conference posters. If you have a trip coming up, I have a recommendation [5:15] for how you can make this so much more convenient with the electronic SIM card or eSIM from Saily. [5:24] What's it good for? If you're traveling, you can avoid roaming fees just by switching to a local [5:30] eSIM. That can save you a ton of money. 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