11 June 2026

#312 Sabrina Pasterski - Theoretical Physicist on the Hidden Code of the Universe

0Frameworks

12Insights

Insights & moments

The myth-busts, hot takes, explainers, and tools worth keeping.

Myth Buster· 1

Myth Buster1:29:30

What Actually Happens If You Fall Into a Black Hole

Sabrina corrects the popular idea that crossing a black hole's event horizon is instantly violent: for a large enough black hole, you wouldn't necessarily notice the crossing right away, since the horizon itself isn't physically special at that scale. The real problems (paradoxes, information loss, 'spaghettification') show up closer to the singularity, and mostly reveal that physicists' assumptions break down rather than that anything mystical happens.

Crossing a large black hole's event horizon isn't necessarily noticeable at the moment it happens
The famous paradoxes (unitarity, thermal radiation) come from trying to place quantum fields on a classical black hole background
'Spaghettification' happens later, as curvature grows extreme near the singularity
She reframes these as unresolved assumptions in our models, not proof that 'physics is broken'

“when you first go through, you don't really know that you went through because like it's the black holes can be different sizes”
Sabrina · 1:29:30

“it's not breaking physics it's showing that there is something broken in our assumptions”
Sabrina · 1:27:30

#black-holes#physics-explainer#myth-busting

Hot Take· 5

Hot Take1:23:00

Playing Devil's Advocate for Flat Earthers, For a Second

Answering a Patreon question about the roughly 1-in-10 Americans who say they believe the earth is flat, Sabrina briefly tries to steelman the flat-earth position before dismantling it: everyday intuition (a flat map, a flat street) works fine at small scales but breaks down when applied beyond its scope, which is why satellite imagery, GPS, and curvature-dependent systems settle the question.

Everyday flat-earth intuition works locally (driving around town) but fails when applied beyond the scale it was built for
Satellite images and views from space are the most direct visual proof the earth is round
GPS and satellite communication systems only work correctly if you model the earth as curved
She frames flat-earth belief as a case study in trusting visceral intuition beyond where it's actually valid

“look at the pictures from damn like satellites or or like people up in space you could see the horizon”
Sabrina · 1:23:30

“you're trying to apply a framework beyond its scope of applicability”
Sabrina · 1:24:30

#flat-earth#science-communication#hot-take

Hot Take50:00

From Childhood Hero to Skeptic: Her Complicated Elon Musk Journey

Sabrina traces how her view of Elon Musk shifted from idolizing him as a kid (he 'liked physics,' so she wanted to too) to a period of resentment over what she saw as overselling and buzzword-driven hype in tech versus the underfunded, slow grind of real physics research, and finally to renewed appreciation now that AI coding tools born from that same hype are actually useful to her work.

She idolized Musk as a kid partly because he 'liked physics,' shaping her own decision to study it
She went through a disillusioned phase, resenting tech figures for overselling buzzwords next to underfunded 'real' physics
She credits getting people onboard with a shared vision as genuinely valuable, as long as the vision is achievable
Ironically, the same hype cycle produced AI coding tools she now finds genuinely useful in her research

“He was my hero as a kid and then I went through different phases of how I feel about the guy.”
Sabrina · 50:00

“there's a lot of value to being able to get other people on board with the same vision because then you can really push for…”
Sabrina · 51:30

#elon-musk#tech-hype#hot-take#career-reflection

Hot Take2:13:00

Who's Actually Winning the US-China Physics Race

Asked directly who's ahead in physics between the US and China, Sabrina says the US is still ahead overall, but argues the real difference is structural: America's elite, exclusionary hiring pipeline (Ivy League-in, Ivy League-out) leaves many capable researchers unemployable in the US system, while China is willing to fund researchers and experiments the US wouldn't prioritize, including work with no near-term military or IP value.

She believes the US remains ahead in physics overall
The US pipeline funnels almost exclusively through a handful of elite institutions, shutting out otherwise capable researchers
She sees value in China funding 'unglamorous' physics experiments the US taxpayer wouldn't prioritize
Because fundamental research is published openly on arXiv, she argues this isn't really an IP or security race the way military tech is

“isn't it great that like they spend their money on the things that we don't value doing”
Sabrina · 2:15:30

“we are ahead”
Sabrina · 2:15:00

#us-china#science-policy#hot-take#academia

Hot Take58:00

Why the 'Blue Sky Research' Funding Pitch Feels Dishonest to Her

Sabrina critiques the standard justification for public physics funding — 'quantum mechanics gave you the transistor, so trust us with the next thing' — as an unconvincing appeal to past payoffs rather than a real argument. She'd rather see the field build tangible, valuable infrastructure and IP that funds itself, similar to how CERN's data-sharing needs contributed to the early web.

She's uncomfortable with the standard pitch that past breakthroughs (transistors, GPS) justify continued blank-check funding for unrelated blue-sky research
She wants theoretical physics to build genuinely valuable infrastructure/IP rather than relying purely on taxpayer goodwill
She cites CERN's role in the early internet/web as a model for research infrastructure paying real dividends
She frames this as a chance to redesign how the field funds itself instead of 'begging for things to have been different'

“it's a weird pitch to try to say oh it's worked before so keep giving me money now I don't it doesn't feel honest”
Sabrina · 1:02:00

“can you innovate in that space of trying to fund or have self-funded valuable enterprises that are not driven by profit”
Sabrina · 57:30

#science-funding#academia#hot-take

Hot Take2:19:00

Her Honest Take on UFOs, UAPs, and the Nimitz Sighting

When pressed on UFO and UAP sightings, including the Nimitz incident, Sabrina says she wishes they were real alien contact because it would be more interesting, but leans toward mundane or classified-military explanations, or people over-extrapolating from limited visual evidence. She's more struck by how confidently people assume 'alien' technology would be exempt from the same physical laws that constrain us.

She believes life likely exists elsewhere statistically, but is skeptical of claims we've been contacted
She suspects many UAP sightings are either classified military tech or people misreading limited visual evidence
She questions why observers assume alien technology could bypass the same physical laws that constrain human engineering
She flags that AI-generated imagery will soon make this kind of evidence even harder to trust

“I wish I wish they were real. It'd be cooler.”
Sabrina · 2:19:00

“I don't think I I believe in aliens, but I don't believe in like aliens that have contacted us.”
Sabrina · 2:19:00

#ufos#uap#hot-take#aliens

Explainer· 3

Explainer02:30

String Theory vs. Quantum Computing, Explained Plainly

Sabrina untangles a common public confusion right at the top of the interview: string theory and quantum computing are not the same field, even though people often conflate them. She frames her whole discipline's goal as trying to piece together the underlying laws of nature through mathematical consistency rather than direct measurement, since you can't run an experiment for physics at the very shortest or longest distance scales.

String theory is not the same as quantum computing or quantum information, despite public conflation of the two
Physicists use mathematical consistency of frameworks to infer laws of nature they can't directly measure
The central problem string theory addresses is reconciling short-distance and long-distance physics rules (e.g. having a working graviton)
In practice a theorist studies one narrow facet of a mathematical framework and tries to generalize it

“basically the whole point is we want to try to as a field not individually understand like what the basic rules are what are the…”
Sabrina · 03:00

“string theory is one example of a uh route that people have found to kind of avoid the pitfalls of like understanding how to have…”
Sabrina · 03:30

#string-theory#physics-explainer#quantum-computing

Explainer1:06:30

Gravitational Memory Effect: A Permanent Imprint Left in Space

Sabrina walks through the older, established version of the gravitational memory effect using a buoy analogy: two detectors sitting far apart will permanently shift position, by a calculable amount, after a gravitational wave from a cosmic collision passes through. Unlike a water wave, this shift encodes real information about the energy of the event that caused it, and the shift stays until something else moves it.

Colliding massive bodies (e.g. merging black holes) send gravitational wave ripples through spacetime
Two far-apart detectors will permanently change distance from each other after a wave passes
The buoy analogy: unlike an ordinary water wave, this shift has a universal relationship to the energy of the event, so you can infer the event's kinematics from the shift
The imprint is technically permanent (until another event moves it again), which is why it's called a 'memory'

“there is like a very like long time scale thing that's imprinted because of this scattering process”
Sabrina · 1:07:00

“it will leave an indention, an imprint in the fabric of space... Yep. Exactly.”
Sabrina · 1:11:00

#gravitational-waves#physics-explainer#black-holes

Explainer1:36:00

Is the Universe a Hologram? Celestial Holography Explained

Sabrina explains her current research field, celestial holography: an attempt to describe our 3D-plus-time universe using an equivalent theory that lives on a 2D boundary (the 'celestial sphere' of the night sky), the same trick physicists use in black hole thermodynamics and string theory's AdS/CFT duality. She's careful to caveat that this is a mathematical equivalence, not necessarily proof that reality is 'literally' a projection.

Celestial holography maps observables in the universe onto the night sky ('celestial sphere') to make otherwise-intractable calculations easier
It follows the same core idea used by Hawking's black hole thermodynamics and string theory's AdS/CFT duality: quantum gravity is easier to describe via an equivalent non-gravitational boundary theory
The goal is extending holography to flat, scattering-relevant spacetimes rather than the artificial anti-de Sitter spacetimes string theorists usually use
She stresses this is a useful mathematical equivalence, and cautions against over-interpreting it as a literal claim that reality 'is' a hologram

“celestial sphere literally is, you know, night sky stars.”
Sabrina · 1:36:30

“I would say in some sense, yeah, by definition, but like how physical is it?”
Sabrina · 1:40:30

#holography#quantum-gravity#physics-explainer#string-theory

Story· 2

Story10:00

How a Photo Book of Her Homemade Airplane Got Her Off MIT's Waitlist

Between ages 12 and 14, Sabrina built a single-engine Zenith kit plane, and her dad turned that project into a networking campaign: FAA officials, air show contacts, and eventually MIT faculty were approached in person with a photo book and business cards documenting the build. Rejected by Harvard and waitlisted at MIT, she credits that years-long relationship-building for getting a faculty member to vouch for her once she was on the waitlist.

Carried a physical photo book and business cards showing her airplane build to introduce herself to gatekeepers face to face
Used being a young, non-threatening kid as low-friction access that credentialed adults don't get
Built relationships with FAA officials and MIT faculty years before applying to college
A contact she'd cultivated eventually vouched for her application once she landed on the MIT waitlist

“it's very easy to network when you're a cute little kid. You don't have to be good at public speaking.”
Sabrina · 10:30

“you have little like photo books of the plane, little business cards”
Sabrina · 25:00

#networking#college-admissions#childhood#mentorship

Story1:11:30

The PhD Discovery That Got Stephen Hawking Citing Her Work

Early in her Harvard PhD, Sabrina found a variant of the gravitational memory effect tied to angular momentum instead of energy loss, work that Stephen Hawking cited in 2016 and that made her dissertation only the second Harvard physics PhD ever published in Physics Reports. She's candid that timing and luck played a big role, since she leaned on simpler electromagnetism math rather than the more advanced coursework most peers relied on.

She discovered the angular-momentum ('spin memory') variant of the gravitational memory effect by connecting it to underlying symmetries
Stephen Hawking cited her solo and joint papers in 2016
Her dissertation became only the second Harvard physics PhD published in Physics Reports
She credits leaning on simpler electromagnetism math (rather than advanced coursework) for making the discovery accessible to her early in her PhD

“I discovered a variant of this based on the connection to the symmetries.”
Sabrina · 1:11:30

“I have a fun result pretty early on in my career but it's like it's a lot of luck”
Sabrina · 1:12:30

#gravitational-waves#career-story#physics-research

Takeaway· 1

Takeaway2:06:30

How AI Coding Tools Are Quietly Changing Theoretical Physics

Sabrina describes trying to build a research tool at Perimeter Institute by hiring student interns to code it, a project that stalled because she couldn't manage people on a task she didn't fully understand herself. Within a few weeks of having access to AI coding tools, she rebuilt the same tool solo, which she says is opening up entirely new kinds of research questions that used to be dismissed as not worth an individual physicist's time.

She previously tried and failed to get student interns to build a research tool for her at Perimeter Institute
AI coding tools let her rebuild the same tool solo within a few weeks
This removes the old excuse that certain systematic, brute-force physics questions 'aren't worth doing' because no individual could justify the engineering time
She now sees herself experimenting with parsing/organizing the physics literature corpus using AI, purely because it's newly possible

“within a few weeks, like I could basically redevelop the same thing with cloud code, which is like amazing”
Sabrina · 2:07:00

“I'm getting into being a shitty vibe coder and just seeing like getting to have fun”
Sabrina · 2:25:30

#ai-tools#vibe-coding#physics-research#productivity