Snapshot · Dwarkesh Podcast
Sagittarius A*, the black hole at the centre of the Milky Way, weighs many millions of times the mass of the Sun, confirmed by tracking the orbits of stars around it over decades.
Where this was said
At 1:17:10 · chapter starts 1:13:03
Dwarkesh pushes on the accounting: if you extract 100% of a brick's energy, what happened to the protons and neutrons? Brown gives the classical answer — they fall into the black hole, and nucleon number is still conserved if you count the black hole itself. Then he opens the quantum mechanics Pandora's box: Hawking and Bekenstein showed black holes radiate and eventually evaporate, and when they do, almost none of the energy comes out as nucleons. The nucleon number is simply gone. This is a clue, Brown says, that quantum gravity violates global symmetries — a teaser for future episodes.
From outside, you never see someone cross the event horizon — they slow, redshift, and fade. From inside, the infaller notices nothing unusual at the horizon. For a galactic-mass black hole, you could cross the event horizon, live your entire life inside, have descendants, and only die when you reach the singularity. Two observers, one event, radically different stories.
We've seen black holes three ways: by tracking stars orbiting Sagittarius A* for decades, by feeling gravitational waves from black hole mergers with LIGO, and by directly imaging the radio glow of infalling matter with the Event Horizon Telescope. Each method independently confirms what was once thought mathematically monstrous.
The first gravitational wave event detected by LIGO in late 2015 was caused by two black holes each weighing about 30 solar masses merging 1.6 billion light-years away.
The first LIGO gravitational-wave signal originated from a black hole merger approximately 1.6 billion light-years from Earth, meaning the event occurred 1.6 billion years ago.
Animals first sensed light 540 million years ago, triggering an evolutionary acceleration known as the Cambrian explosion within 10 million years.
It is estimated that half of all cortical activity in the human brain is involved in visual function, underscoring vision's central role in intelligence.
Cognitive neuroscience literature shows that by age 6, humans can recognize tens of thousands of different object categories — far more data than early AI systems were trained on.
Only about 3% of FDA-approved drugs have genuinely unclear mechanisms of action, making an unknown mechanism a meaningful early red flag for any compound.
Even compounds that clear preclinical testing often fail in humans: 30 to 50% of drugs entering phase 1 trials do not advance to phase 2, frequently because human behavior differs from animal models.
More than 80% of published BPC-157 research comes from a single academic group whose researchers have IP and commercial interests connected to the molecule, limiting independent replication.
Roughly 100 peptide drugs are already FDA-approved, about 150 more are in clinical trials, and 600–700 are in preclinical development, underscoring the legitimacy of peptide science broadly.
The scientist who discovered BPC-157 refused to disclose the screening method used to identify the compound and has never fully published the parent protein sequence — what Peter Attia calls 'scientific trust me, bro.'
The brain's visual, auditory, and motor cortices light up nearly identically whether an experience is real or imagined, making visualization a form of actual neural training.
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