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.
The widely cited ego-depletion model — the idea that willpower is a finite resource that gets depleted — failed to replicate in follow-up studies.
Humans are estimated to have 5,000–7,000 thoughts per day, yet can recall essentially none of them afterward, highlighting why in-the-moment emotional tracking matters.
A large Harvard study found that a wandering mind is an unhappy mind — people report greater happiness when their attention is tethered to the present, even if the task is unpleasant.
A key study finding that we have a 'credit card's worth of plastic' in our bodies was likely skewed because researchers used nitrile gloves that shed plastic particles onto the microplastic detector.
Emotionally sensitive people have a hyperactive amygdala, an underactive prefrontal cortex, and a frayed connection between the two — making emotional regulation structurally harder.
Rejection sensitivity can be observed as early as age 2 or 3, suggesting it has strong developmental and likely genetic roots.
A Yale study found that non-judgmental observation of emotions — without rushing to resolve them — reduces activation in the brain, making it a powerful regulation tool.
Dan Gilbert's research found that the psychological immune system — the brain's ability to justify and find satisfaction in choices — activates most powerfully when a decision is perceived as irreversible.
Barry Schwartz's research found that maximizers — people who try to optimize every decision — tend to achieve objectively better outcomes but report lower happiness than satisficers who choose 'good enough.'
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